United States
Environmental Protection
Agency
Office of Pesticides &
Toxic Substances
Washington, DC 20460
EPA-560/3-80-001
November, 1980
Toxic Substances
Proceedings of the National
Workshop on Substitutes
for Asbestos
Sponsored by:
The Environmental Protection
Agency
The Consumer Product Safety
Commission
The Interagency Regulatory
Liaison Group
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EPA-560/3-80-001
November 1980
PROCEEDINGS OF THE
NATIONAL WORKSHOP ON
SUBSTITUTES FOR ASBESTOS
Arlington, VA, July 14-16, 1980
Sponsored by:
United States Environmental Protection Agency
United States Consumer Product Safety Commission
Interagency Regulatory Liaison Group
Arlene Levin, Co-editor
Contract flo., ,68-02-3168
Task 17
EPA Project Officer and Co-editor: Hope Pillsbury
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Pesticides and Toxic Substances
Washington, D.C. 20460
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DISCLAIMER NOTICE
Convention of the National Workshop on Substitutes for Asbestos and
publication of this document do not signify that the contents necessarily
reflect the joint or separate views and policies of each sponsoring Agency.
Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
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PREFACE
The purpose of the National Workshop on Substitutes for Asbestos was to
obtain more information on the technical and economic feasibility and
possible health problems of substitutes for asbestos, for use in considering
regulation of asbestos. The Workshop was co-sponsored by the Environmental
Protection Agency (EPA), the Consumer Product Safety Commission (CPSC), and
the Interagency Regulatory Liaison Group. It was held at the Sheraton
National Hotel in Arlington, Virginia, July 14 to 16, 1980. It was attended
by over 600 people from industry, government, public interest groups, labor,
and other interested parties.
Most of the technical/economic portion of the workshop consisted of talks
on substitutes for asbestos product categories, followed by question and
answer periods. Eight roundtable discussion sessions were held concurrently
for each category of substitutes for asbestos. An evening panel discussion
was held in which representatives from industry, government, labor, and
environmental groups discussed substitutes for asbestos. On the second day
of the workshop, a session was held in which manufacturers and other experts
on asbestos supplied information about substitute materials and products.
The second portion of the workshop focused on health effects of both
fibrous and nonfibrous types of substitutes. An overview on routes of expo-
sure was presented, followed by papers on epidemiological and experimental
studies of various substances that can ^e used as substitutes for asbestos.
Discussion sessions followed the presentations. An evening session was held
to discuss the health aspects of exposure to talc.
Chairmen
Richard J. Guimond and James N. Rowe, Ph.D.
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
iii
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CONTENTS
Acknowledgments viii
Introductory Remarks, Richard J. Gulmond *
Overview of Regulatory Status, Peter Preuss and Warren Muir 3
ECONOMIC SESSIONS: Richard J. Guimond, Chairman
WORK SESSION ON FRICTION PRODUCTS
Non-Asbestos Friction Materials, Michael G. Jacko, Charles M.
Brunhofer, and F. William Aldrich 9
Discussion on Friction Products 32
WORK SESSION ON GASKETS AND PACKINGS
Gaskets and Packings, Stephen D. Koehler 35
Discussion on Gaskets and Packings 58
WORK SESSION ON PLASTICS AND FLOORING
Asbestos in Plastics: Looking for Alternatives, Matthew Naitove 59
Discussion on Plastics and Flooring 69
WORK SESSION ON PAPER AND ROOFING PRODUCTS
Single-Ply Roofing as a Substitute for Asbestos Roofing Felt,
David E. Bailie 71
Roofing Felt, Nancy Roy 75
Discussion on Roofing Products 82
Mill Applied Coatings for Underground Pipelines, Jack Wink 84
Discussion on Pipeline Wrap 99
WORK SESSION ON TEXTILES
Textiles, Samuel G. Manfer 101
Discussion on Textiles 106
WORK SESSION ON SEALANTS
Asbestos Substitutes in Roof Coatings, Kenneth Brzozowski 109
Overview of Asbestos Substitutes in Sealants, Roof Coatings, and
Cements, Eric Wormser 113
Discussion on Sealants 119
WORK SESSION ON SUBSTITUTES FOR ASBESTOS-CEMENT SHEET
Glass Fiber Reinforced Cement, John Jones and Frank W. Fekete 121
Other Substitutes for Asbestos-Cement Sheet, David Cogley 129
Discussion on Substitutes for Asbestos-Cement Sheet 135
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WORK SESSION ON SUBSTITUTES FOR ASBESTOS-CEMENT PIPE
Substitutes for Asbestos-Cement Pipe, Richard A. Simonds and
James L. Warden 139
Discussion on Substitutes for Asbestos-Cement Pipe 161
PANEL ON DEVELOPMENT OF SUBSTITUTES
Presentations by Richard J. Guimond, Robert Moore, John Gurtowski,
Roy Steinforth, James F. Reis, and Barry Castleman 163
Discussion on Development of Substitutes 175
ROUNDTABLE DISCUSSION SESSIONS
Introductory Material to Roundtable Discussion Sessions 181
Summaries of Roundtable Discussions 194
PRODUCT AND SUBSTITUTE MATERIAL REVIEW SESSION 229
HEALTH SESSIONS: James N. Rowe, Ph.D., Chairman
Scope of the Health Workshop, James N. Rowe 279
OVERVIEW OF THE ROUTES OF EXPOSURE
Inhalation, Deposition, and Clearance of Particles,
Morton Lippmann 283
Fate of Ingested Particulates, James Millette and
M. Rosenthal 313
Discussion on the Routes of Exposure 323
SYNTHETIC FIBROUS SUBSTITUTES
Man-Man Vitreous Fibers and Health, Jon L. Konzen 329
Discussion on Man-Made Vitreous Fibers 342
The Translocation and Fate of Sized Man-Made Mineral Fibers
Following Exposure by Intratracheal Instillation in Rats,
David M. Bernstein, Robert T. Drew, and Marvin Kuschner 343
Discussion on the Translocation and Fate of Sized Man-Made
Mineral Fibers 391
Occupational Exposures to Mineral Wool, Douglas P. Fowler 395
Discussion on Mineral Wool 418
Mortality Patterns of Rock and Slag Mineral Wool Production
Workers, Cynthia F. Robinson, Gregory 0. Ness, Richard J.
Waxweiler, and John M. Dement 419
Discussion on Rock and Slag Mineral Wool 420
Industrial Hygiene and Toxicology Aspects of 3M Nextel 312
Ceramic Fibers, Robert S. Larsen and William McCormick 425
Discussion on Ceramic Fibers 441
Toxicology of Aramid Fibers, C. F. Reinhardt 443
Discussion on Aramid Fibers 448
Environmental Exposure Considerations Due to the Release of
Graphite Fibers During Aircraft Fires, Benjamin Sussholz 451
Discussion on Graphite Fibers 474
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NATURAL FIBROUS SUBSTITUTES
Cross-Sectional Medical Study of Wollastonite Workers,
Brian Boehlecke, D. M. Shasby, M. R. Petersen, T. K. Hodous,
and J. A. Merchant 475
Discussion on Wollastonite * 476
Endemic Pleural Disease in Relation to Zeolite Exposure,
Arthur N. Rohl 477
Discussion on Zeolites in Turkey 482
Chemical Detoxification of Asbestos Fibers, Earl S. Flowers 489
Discussion on Chemical Detoxification of Asbestos Fibers 497
NATURAL NON-FIBROUS SUBSTITUTES
Health Considerations in the Perlite Industry, W. Clark Cooper 505
Discussion on Perlite 511
Review of the Health Effects of Micas, Ilmar Lusis 513
Discussion on Mica 554
Health Effects of Venniculite, James E. Lockey and
Stuart M. Brooks 555
Discussion on Venniculite 560
Talc: Roundtable Discussion (Evening Session)
Opening Remarks: Natural Non-Fibrous Substitutes: Talc,
Arthur M. Langer 563
Cross-Sectional Epidemiologic and Industrial Hygiene Survey of
Talc Workers Mining Ore from Montana, Texas, and North Carolina,
John Gamble, Alice Greife, and John Hancock 570
Roundtable Discussion on Talc 612
SYNTHETIC NON-FIBROUS SUBSTITUTES
Occupational Exposures in the Manufacture and Application of
Polyurethane and Urea Formaldehyde Insulation Systems,
Robert F. Herrick, A. A. Alcarese, R. P. Reisdorf, and
D. W. Rumsey 621
Discussion on Foams 644
Human Pulmonary Function Study (5 years) on Occupational
Isocyanate Exposure, Hans Weill 647
Discussion on Isocyanate 652
CRITERIA FOR EVALUATING SUBSTITUTES
Criteria for Animal, Tissue Culture, and Biochemical Studies
on Asbestos, Mineral Dusts, and Proposed Substitutes for
Asbestos, Earl S. Flowers 653
vii
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ACKNOWLEDGMENTS
We gratefully acknowledge all who aided in organizing and producing the
Workshop on Substitutes for Asbestos. The Chairmen express special thanks
to the speakers and participants, who provided much insight and information
about the subject.
The editing work on the Proceedings, performed by the EPA and CPSC staff
and their contractors, GCA Corporation and Merenda Associates was also very
much appreciated.
viii
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INTRODUCTORY REMARKS
by
Chairman Richard J. Guimond
U.S. Environmental Protection Agency
Washington, D.C.
Welcome to the first National Workshop on Substitutes for Asbestos. I
will be chairing the technical and economic sessions of this workshop.
We hope you find the meeting informative. I have been looking through
the presentations and I have found much that I was not aware of before and
much that has expanded our horizons.
There are going to be eight Roundtable discussions. There is a list of
questions, issues, and topics that we would like to take up in those Round-
tables. The first page of the handout for the Roundtable discussion is a
general set of questions that apply to all Roundtable discussions, but the
remaining pages focus on the individual sessions. There is a session for
asbestos friction products, reinforced plastics, flooring, gaskets and pack-
ings, paper and roofing products, textiles, asbestos cement sheet, and asbes-
tos cement pipe. People are free to move around the various sessions, in
case you want to learn about more than one topic or participate in more than
one session.
Because of the large number of participants attending the meeting, I am
going to ask that all remarks or questions be held to 3 minutes, so that
everyone has an opportunity to ask a question or to make their comment.
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REGULATORY STATUS
by
Dr. Peter Preuss
U.S. Consumer Product Safety Commission
Washington, D.C.
and
Dr. Warren Muir
U.S. Environmental Protection Agency
Washington, D.C.
DR. PETER PREUSS
We are here at this workshop to try to learn from you about an issue that
is of a great deal of concern in many places. Some of you may not be entirely
familiar with the Consumer Product Safety Commission (CPSC) and what we do and
how we function. The Consumer Product Safety Commission is an independent
agency headed by five commissioners and a chairman appointed by the President.
Basically, we administer two statutes that allow us to deal with and regulate
asbestos, other hazardous materials, and health and safety issues related to
consumer products.
Under the Consumer Product Safety Act, the Commission has the general
responsibility to protect the public from unreasonable risks of injury, illness,
or death associated with consumer products.
The second Act, the Federal Hazardous Substances Act, allows us to regu-
late hazards presented by the presence or use of toxic and other hazardous
substances.
In the past, the agency has used both of these Acts in controlling sub-
stances they felt posed a hazard. Regardless of which statute we have used
in the past or which we might use in the future, one of the keys to effective
regulation is having not only good communication from all involved parties,
but also having regulations that are based on good and appropriate information.
This has been one of the issues that 1 have been speaking about ever since I
came to the Commission about a year ago because it has troubled me that there
has not been a sufficient flow of information. And whether it was at the meet-
ing of the Asbestos Information Association or a variety of other forums where
I have been privileged to represent the Commission, I have tried to make this
point: that our regulations and our efforts are, indeed, limited by the quan-
tity and quality of the information that we have available to us at the time
that we make our decisions.
3
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Now, on this issue specifically, that is the use of asbestos and asbestos
substitutes, we have made a number of attempts over the past 8 or 10 months to
try to acquire some of the information that we felt was important and necessary.
In October of last year, the Commission, together with EPA, published an
Advanced Notice of Proposed Rulemaking (ANPRM) where we, in general, outlined
our thinking and our approaches to the question. CPSC, in particular, tried to
get some idea of the scope of the potential problem posed by consumer products
containing asbestos. A number of very specific questions were asked at that
time.
And since then, we have followed through in the direction that ANPRM had
indicated. Very recently, the Commission has voted to approve a General Order
that requires the submission of information about the use of asbestos in a
variety of consumer products. The point is to obtain some very specific infor-
mation for a number of defined and specified consumer products. We hope that
these kinds of efforts will provide us with the information that is important
and necessary to make our decisions.
In addition, we have just completed setting up a test facility in Chicago
to look at asbestos and other fibers as they may be emitted from consumer
products. That laboratory is now beginning to look at many materials and prod-
ucts. This kind of effort will become more important and the information we
gather will become more important as we move from asbestos to some of the
substitute materials.
I think one of the points of this workshop is that if we have learned
anything from our past efforts, it really is very important to try to accumulate
the information and assess and evaluate the information before we go too far
down any one road. We cannot wait until materials are in widespread use, until
everybody is exposed, or until they are present in all parts of the environment
before we begin to look at deleterious health effects.
So we are looking forward, during these 3 days, as a regulatory agency, to
obtaining some of the information dealing with the identity, the uses, and the
possible adverse health effects from consumer exposure to this potentially very
large group of materials that we are, for convenience, calling "asbestos
substitutes."
I want to point out that this workshop, although the headings indicate
"EPA/CPSC," is more than just an effort of these two agencies. It is, indeed,
an effort that is being coordinated by all of the agencies belonging to the
IRLG, the Interagency Regulatory Liaison Group, which is composed of five
agencies. In addition to the EPA and CPSC, there is the Food and Drug Admin-
istration, the Occupational Safety and Health Association, and the Food Safety
and Quality Service of the Department of Agriculture. I mention this because
these IRLG agencies have been working very hard over the past year on this
topic of asbestos and asbestos substitutes to try to make sure that we are
sharing information; that we are not stepping on each other's toes', that we
are not duplicating efforts; that we make sure what we are doing is as coherent
and as reasonable as we can possibly make it so that this workshop and the
information that comes from it will clearly be shared with all of those
agencies.
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Again, these agencies, the IRLG agencies, have been looking for ways to
foster communication and to try to be a little bit more innovative than in the
past. Hopefully, this workshop will serve as a model for that effort, and so,
after the 3 days are over, we will all agree that we have benefited from this
exercise. We will have benefited particularly by learning a great deal from
you; by learning a little better what our needs are; and jointly, by under-
standing how we can communicate a little bit better with each other.
The workshop is structured in a way to allow maximum participation by all
of the people who are attending. And to get those of you who, clearly, know
much more about many of these specific areas to participate with us and to try
to share knowledge. The sessions will cover a variety of topics, everything
from physical uses to health effects. I think you all have an obligation to,
in fact, participate with us in these efforts so that we can make this work-
shop a success. And, again, I think that the more informed we are, as
regulatory agencies, as we proceed in our regulatory investigations, the better
our chances are of obtaining the best results.
DR. WARREN MUIR
We in the Office of Pesticides and Toxic Substances are currently con-
ducting a rulemaking investigation on the commercial and industrial uses of
asbestos. We are holding this conference as part of our investigation in an
effort to expand our knowledge regarding the substitutes of asbestos. We want
to learn as much as possible about asbestos substitutes in various product
categories. We are eager to learn about their performance, their cost, and
any health and environmental risks that they may pose. This rulemaking pro-
ceeding is being conducted under the Toxic Substances Control Act, more often
referred to as TSCA. The Act required that EPA eliminate unreasonable risks
of human and environmental injury posed by chemical substances.
Several factors are involved in evaluating whether or not asbestos, or any
chemical substance or mixture, presents an unreasonable risk. To promulgate
a rule to control risks from exposure to asbestos, the EPA plans to consider
the following three things and, indeed, such factors would weigh into any
control regulation under the Toxic Substances Control Act.
The first of these is the hazard of asbestos on health and the magnitude
of exposure to humans. Secondly, the benefits of asbestos from its various
uses and the availability of substitutes. And thirdly, the reasonableness of
the ascertainable economic and regulatory impact of any rulemaking that we
would undertake. These three factors would enter into, generally, any regu-
latory action that we would take.
EPA's preliminary health assessment, which we have been undertaking, indi-
cates that asbestos poses a substantial risk to human health. The various
toxicological characteristics of asbestos have been well known for many years
and our assessment has, in essence, confirmed those relatively well known
characteristics.
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This conclusion has prompted our initiation of the rulemaking proceeding.
In deciding on the specifics of such a rule, we felt it appropriate to investi-
gate the substitutes of asbestos; and, hence, we are interested in participating
with the Consumer Product Safety Commission in undertaking this workshop. We
wanted to make sure that we had made a careful examination of the availability
of reasonable substitutes for the various uses of asbestos and, therefore, we
are investigating both those substitutes already available commercially and
those anticipated to be available in the near future.
EPA wants to know about the good and bad characteristics of the substi-
tutes so that our decisions will reflect the best information available. This
workshop is one of our efforts aimed at gathering and evaluating such informa-
tion. As Dr. Preuss has pointed out, our ability to undertake these actions,
in any reasonable fashion, is really predicated upon a good information phase.
Other information collection actions include contractor studies and com-
ments on an Advanced Notice of Proposed Rulemaking that we had in the Federal
Register. Under our current schedule, we expect to complete our deliberations.
to the extent that the agency could propose a suitable role regarding commer-
cial and industrial uses of asbestos by this winter. This will be a proposed
rule.
We expect that this workshop will provide us with valuable data and in-
formation, as well as perceptions of the industry, environmentalists, academia,
and the public. The more informed we are, as we proceed in our regulatory
investigation, the better our chances of obtaining an optimal result, namely,
the elimination of unreasonable risks from exposure to asbestos while minimizing
the adverse impacts of such a regulation.
We have structured this workshop to provide us with a broad array of view-
points regarding the substitutes of asbestos. We have representatives from
companies that use asbestos to achieve various product characteristics; those
that are suppliers of asbestos; manufacturers of substitutes; research scien-
tists; concerned private citizens, and others. We also have representatives
from industry and elsewhere on the possible asbestos substitutes currently
available or projected.
I would like to focus on some of the specifics about the workshop. The
kind of information we are looking for covers substitutes for the many uses
that have been found for asbestos. We want to know about their technical per-
formance, their economics, and their effects on human health through the
environment.
We have divided these uses into eight product specific categories, which
are friction products, gaskets and packings, plastics and floorings, paper
products, textiles, sealants, asbestos cement sheet, and asbestos cement pipe.
This will enable all of us to focus on specific areas of interest and concern,
and will help us obtain information and advice from the most qualified people
in each of the respective fields. The technical performance of asbestos and
the economic aspects of developing, marketing, and using asbestos substitutes
will be discussed within each of the category review sessions.
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In evaluating substitutes our initial step is to determine the range of
uses within each.product category. From this we can find out where substitutes
are available for product categories or subsets of categories and how they per-
form technically. We want to look at both the general fiber substitutes for
asbestos and at substitutes for specific asbestos products. We want to know
about the technical limitations of the substitutes present; for what applica-
tions are there no feasible substitutes; and how much has been invested in
research and development to find such substitutes.
We are also concerned about the economic and practical impacts of conver-
sion to asbestos substitutes. We are aware that there are many situations
where economics may prevent*the use of a substitute. Where has this occurred,
and how might the situation be improved? What are the estimated conversion
costs in the various product industries? Would industry requirements be
altered significantly, and are there performance standards and regulatory
guidelines that might encourage or inhibit the production or introduction of
any such substitutes? These are a few of the topics for the Round Table
sessions.
And, finally, we will be addressing the health aspects of various fibrous
and nonfibrous substitutes, both synthetic and natural. We will review the
routes of exposure and the results of exposure to various substances, many as
reported in studies and surveys of exposed workers in several industries.
We have set aside some time for open discussion on the evaluation of cri-
teria for health studies and on the scientific evaluation of substitutes. We
are here to learn; we have come with open eyes and open ears. We hope that
you will do the same. We want to know all sides of the issue, the essential
uses for asbestos, those applications for which there are no feasible substi-
tutes yet available, and those for which substitutes exist and may even be
superior.
The workshop is not the end of our search for information. We hope that
it will stimulate your thoughts and generate new ideas. So, if you have any
additional data, information or comments, or wish to elaborate on any of the
discussion that has occurred during the workshop, we would encourage you to
make that available to us.
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NON-ASBESTOS FRICTION MATERIALS
by
Michael G. Jacko, Ph.D.
Bendix Advanced Technology Center
Southfield, Michigan
and
Mr. Charles M. Brunhofer and Mr. F. William Aldrich*
Bendix Friction Materials Division
Troy, New York
ABSTRACT
Friction materials for automotive orakes are complex composites containing three
general types of ingredient materials: reinforcing fibers; modifiers that
adjust or maintain friction level, wear rate, and noise properties; and organic
resin binders. Historically, the foundation or major constitutent of automo-
tive friction materials has been asbestos fiber, so chosen because of thermal
stability, friction level, reinforcing properties, availability, and relatively
low cost.
Numerous substitutes for asbestos in conventional organic materials have been
evaluated, including both naturally occurring and synthetic materials. Direct
substitution of these alternative materials in conventional formulations has
resulted in poor friction levels, friction instability, roughness, structural
failure, increased noise, mating surface deterioration and/or front-to-rear
vehicle brake imbalance. Complete reformulation, not simple substitution, is
necessary to meet the numerous, complex performance requirements of consumers,
manufacturers, and government standards, such as FMVSS 105-75 and FMVSS 121.
In the 1960fs, a new class of friction materials, called semimetallics, was
developed to meet severe braking requirements, primarily in heavy-duty disc
brake and extreme duty truck block applications. Semimetallics operate satis-
factorily against the ventilated cast-iron rotors in the smaller brakes of
downsized cars, as well as against the solid rotors found in the lighter brakes
of new front wheel drive vehicles. Semimetallics rely on steel fiber and pow-
der metallurgy techniques for reinforcement, and do not require asbestos. The
improved performance of semimetallics compensates for their higher costs due
to more expensive ingredients, higher specific gravity, and more costly pro-
cessing requirements. Overall development took more than 10 years from intro-
duction to significant customer acceptance.
*Presented by Mr. Charles M. Brunhofer
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The characteristics of semimetallics make them extremely difficult and costly
to process as a drum lining segment. Consequently, an additional new class of
friction materials is under development, specifically for drum lining applica-
tions. Additional development effort is necessary, not only to confirm the
performance characteristics of these new substitute fiber formulations, but
also to develop new processing techniques. These new-type friction materials
will be more costly, however, due to the ingredients and new processing
techniques.
INTRODUCTION
Automotive brakes can be viewed, quite simply, as energy transformers.
During a brake application, the friction material (stator) makes contact with
the rotating drum or disc (rotor), creating a friction force resisting the
relative motion between the two bodies. The energy of motion is transformed
into heat energy, which is dissipated, primarily through the rotating member.
As one might expect, the friction material must operate in a rather hostile
environment. Lining soak temperatures in excess of 400°C (750°F) are not
unusual, and temperatures at the contact interface can exceed 850°C (1560°F).
The nature of the on-the-road operating environment (dust, mud, salt, water,
etc.) complicates the problem. The friction material must possess an optimized
balance of characteristics, and maintain those characteristics throughout
20,000 to 40,000 miles of vehicle operation.
The fundamental characteristics of friction materials are listed in
Table 1. Friction level must be adequate and stable over a wide range of
operating speeds, application pressures, and temperatures, regardless of the
conditioning and age of the material. Of particular interest are the fade/
recovery characteristics; i.e., the ability to resist friction level deterio-
ration when subjected to extreme elevated temperatures (the fade) and then to
return to the pre-fade friction level on cooling (the recovery). The friction
material must have good wear properties for long life, but it must also not
cause excessive wear or grooving on the mating disc or drum. Excessive com-
pressibility, noise and roughness (chatter, vibration, pulsation) must be
avoided, and sensitivity to moisture must be minimized. Finally, the friction
material must be capable of being manufactured with consistency at a reasonable
cost.
Detailed definitions of these characteristics, and their interaction and
interdependence, have been discussed at length by Aldrich and Jacko.1 In gen-
eral, attempting to improve upon one characteristic often results in the deterio-
ration of other characteristics. The development of friction materials is
therefore a complex, interactive process seeking an optimized combination of
interdependent characteristics.
The existence of numerous brake designs provides another level of com-
plexity in designing friction materials. Linings for drum brakes require a
wide range of properties. The duo-servo drum brake (the most popular U.S.
design) requires two different types of linings, designated primary and
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TABLE 1. CHARACTERISTICS OF
FRICTION MATERIALS
Friction
• Level (coefficient)
• Stability - speed
- pressure
- temperature
- conditioning
- age
• Fade/recovery
Wear
• Friction material
• Drum or disc
Noise
Roughness
Moisture sensitivity
Manufacturability
• Processibility
• Uniformity
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secondary, each of which needs different properties of strength, wear resistance,
friction level and friction stability. The non-servo drum brake (used on many
sub-compact vehicles) requires a friction material which encompasses the best
characteristics of the primary and secondary in a single formulation, with
emphasis on low-temperature properties and static friction capability. The
large hydraulic and air-operated drum brakes utilized on medium and heavy trucks
require, in general, the maximum properties of the smaller vehicle linings but
at significantly higher operating temperatures. The arcuate form of drum brake
linings places additional restrictions on the formulation, because of processing
requirements.
Disc brakes demand a totally different set of operating conditions for the
friction materials. Disc brakes generally operate at significantly higher tem-
peratures than equivalent drum brakes, and the front disc brakes run hotter than
the rear drum brakes on the same vehicle (Table 2). The friction material for
disc brakes must be specifically designed for these higher temperatures, and
must possess a higher coefficient of friction and better wear characteristics
across the temperature range. Friction-material formulations must also be
tailored to the specific needs of the particular vehicle application. Numerous
parameters such as vehicle weight, front-to-rear brake balance, actuating system
design, and duty cycle affect the capability of a particular lining formulation
to perform satisfactorily.
The existence of numerous complex performance standards emanating from con-
sumers, associations, manufacturers, and government agencies provides an addi-
tional set of parameters that friction materials must meet. Significant dif-
ferences can exist between friction materials used as original equipment in new
vehicles and friction materials available as replacement parts in the after-
market. Each vehicle manufacturer has a unique, extensive set of test and
acceptance standards to ensure the safety, durability, and performance of its
products and the components used therein. Government-instituted requirements
exist at the federal, state, and local levels. Federal requirements include
those promulgated by the Department of Transportation (vehicle performance),
the Occupational Safety and Health Administration (manufacturing work practices),
and the Environmental Protection Agency (manufacturing practices and raw
materials).
In order to meet the many characteristics outlined thus far, friction mate-
rials for automotive brakes have developed as complex composites containing
three general types of ingredient materials: reinforcing fibers; modifiers
that adjust or maintain friction level; wear rate and noise properties; and
organic resin binders. Historically, the type of friction materials used in
most automotive applications has been conventional organic friction material.
The foundation or major constituent of conventional organic friction material
has been asbestos fiber, so chosen because of its unique combination of char-
acteristics. Asbestos fibers provide reinforcement, possess a high coefficient
of friction, and more importantly, have excellent thermal stability. The open-
ness of the fiber, its adsorptiveness, and its compactability enhance the pro-
cessing and uniformity requirements. Finally, asbestos fibers have been avail-
able in a variety of grades at a relatively low cost.
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TABLE 2. BRAKE FADE TEMPERATURES3(°F)
(SUBCOMPACT FRONT WHEEL DRIVE
VEHICLE)
1st SAE fadeb 2nd SAE £adeb
(10 stops) (15 stops)
Disc front Drum rear Disc front Drum rear
Combination 1 780 300 870 360
Combination 2 985 235 1030 240
Combination 3 760 200 855 235
Temperatures measured before the last stop. Actual temperatures
for disc brakes are 80 to 180°F higher, as measured below the rub-
bing surface. Surface temperatures are in excess of 1600°F (870°C).
bSAE J843c
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Once the friction material has been cured, the asbestos fibers are locked
into the matrix. During brake operation, the high temperatures generated at
the interface convert more than 99.7 percent of the asbestos to non-fibrous
residues (primarily olivine) in the wear debris,2 and less than 0.02 percent
asbestos becomes airborne.3*1*
The conventional organic formulations and the processes by which they are
made have been dependent upon and tailored to the physical and chemical proper-
ties of asbestos. Two courses of action are open for elimination of asbestos
from automotive friction materials:
1. Develop a new generation of friction materials, designed from
the start without asbestos in mind.
2. Attempt to substitute an alternative fiber system for the
asbestos in conventional formulations, with subsequent mod-
ification of composition and process techniques.
Bendix is aggressively pursuing both courses of action. As Mr. William
Agee, our Chairman and Chief Executive Officer, has stated, Bendix is committed
to being asbestos-free at the earliest possible date within this decade.
SEMIMETALLIC DISC PADS
Properties
In the 1960s, a new generation of friction materials, called semimetallic,
was developed to meet severe braking requirements which organics could not meet.
Class A organics (typical U.S. materials), which perform well in low and mod-
erate temperature duty, are prone to fade and exhibit compressibility and poor
wear resistance at high temperatures. Class B organics (typical European and
Japanese materials) provide good high-temperature wear and friction levels, but
have poor low-temperature wear resistance, produce rotor scoring and/or wear,
and are prone to being noisy. Semimetallies were initially develed for these
extreme, high-temperature applications.5
Semimetallics rely on steel fiber and powder metallurgy techniques for re-
inforcement. Various property modifiers are added to enhance performance to
desired levels, with a resin binder holding the materials in a uniform solid
mass. Semimetallics may contain metallic powder, sponge iron particles, ceramic
powder, steel fiber, rubber particles, graphite powder, and phenolic resin.6*7
Some manufacturers utilize a backing layer of a different composition which
can contain asbestos.
Problems Overcome
Inherent in the uniqueness of the semimetallic formulations and their per-
formance properties were a number of significant problems which required reso-
lution. Concentrated development effort was required to resolve both proces-
sing and performance related issues. Processing issues included: the unifor-
mity of the raw materials mixtures, the ability to form and handle the in-
process material, and the ability to manufacture high-quality parts consistently.
14
-------
Performance issues included: materials strength, cold friction properties,
initial wear resistance, and attachment to the backing plate. The development
effort on semimetallic friction material has been continuous, not only to fur-
ther improve its characteristics and properties, but also to overcome the prob-
lems inherent in accommodating new vehicle applications.
Semimetallics gained acceptance because they were able to solve some of
the problems that could not be overcome using Class A or Class B organics.
The Improvements/advantages are listed in Table 3. The key element is the
attainment of overall excellent properties at both low and high temperatures.
Semimetallics cost more because of more expensive ingredients and a costlier
process, but the improved performance capabilities offset these factors. An
increased usage of Semimetallics has occurred over the past few years. The
downsizing of vehicles, with resulting smaller front brakes and higher oper-
ating temperatures has given impetus to increased use of Semimetallics.8 It
is expected that the trend toward asbestos-free semimetallic disc pads will
continue.
SEMIMETALLIC DRUM LININGS
An obvious alternative to conventional organic drum brake linings is the
use of semimetallic material for drum linings. In fact, one of the first
applications for Semimetallics was for air brakes on heavy-duty trucks used
in the logging industry—an extremely severe application.
Significant development effort has been expended on semimetallic drum
brake linings. However, the basic nature of Semimetallics does not lend itself
to the arcuate segment configuration required for small drum brakes. The semi-
metallic mix does not possess the necessary green strength, is difficult to
bend into the arcuate shape, and is more brittle in its cured form and there-
fore subject to cracking. Modifications to the formulation to facilitate pro-
cessibility generally result in a product that cannot achieve commercially
acceptable performance characteristics.
These difficulties present a clear challenge, and development work on
semimetallic drum brake linings continues.
ALTERNATE FIBERS/REINFORCERS
Properties
Alternative fiber systems in conventional organic formulations represent
the second course of action open to friction-material manufacturers. Table 4
is a summary of the properties of some of the various materials which could
be considered as alternate reinforcements. Since conventional organics and
Semimetallics have traditionally been reinforced with asbestos and steel fiber,
respectively, these fibers are also included in the table for comparative pur-
poses. The data in Table 4 were obtained from the material manufacturer's
literature and extensive characterization data developed at Bendix. Charac-
terization included scanning electron microscopy and x-ray energy spectroscopy
(SEM/XES). The selection of suitable alternate materials must also consider
15
-------
TABLE 3. IMPROVEMENTS OFFERED BY
SEMIMETALLIC DISC PADS
Improved energy absorption
Fade resistance
• Temperature insensitivity
• In-stop fade
• Speed spread
Friction stability (FMVSS 105-75)
Higher temperature capabilities (life)
Rotor compatibility
• Scoring
• Heat checking
Reduced noise
Smaller brake sizing
16
-------
TABLE 4. CHARACTERISTICS OF REINFORCING AGENTS
BANE
MANUFACTURER
OMPOSITXOH
(HEIGBT PERCENT)
COST (e/LB)«*
SHAPE
LENGTH (MM)
DIAHBTER (u»)
ASPECT RATIO
SPECIFIC GRAVITY
TENSILE STRENGTH (PSI)
AVG:
THERMAL STABHITf:
UPPER USE TEMP (^)
Tg (°P)
Tfue <°W
»TTop)
HARDNESS (Mph)
MISCELLANEOUS
INFORMATION
ASBESTOS
JM, etc
3HgO.S102.2B20
SlOj
MgO
1.0
FIBER
250+
0.25*
10,000*
2.56
280-440 KPSI
360 RPSI
1200
1600
3.0 - 4.0
FIBERGIIAS
497
OWENS/CORMlNti
E CLASS
S102 54.5
A120S 14.5
00 17.0
HgO 4.5
B203 8.5
H»20 1.0
5.0
FIBER
3175+
13
240+
2.6
450-550 KPSI
500 KPSI
1300
1350
2000
6.5
SILANIZED
MDIBRAL
FIBER
U.S. PIPE
AMD niUHbHX
S102 42
A120, 8
C«0 35
Hgo a
Other 7
1.9
FIBER
28
1-10
40-60
2.7
3-20 KPSI
70 KPSI
1400
1400
2300
6.0 - 6.5
ALSO HINERAL
WOOL
SDZORITE
MICA
MARIETTA
RESOURCES
SiOj 41
Al20j 16
MgO 21
K20 10
F«0 8
Other 4
0.8
PLATE
3175+
2.7
33-37 KPSI
2960
2.5 - 3.0
FIBERFRAX
(CHOPPED)
CARBORUNDUM
S102 47
Al20j 51
Other 2
5.9
FIBER
305
2
150
2.73
400 KPSI
2300
7.0 - 7.5
VOUASTONITE
MOOD BT
HRERPACE (RT)
CeSlOj
CaO.StOa
S102 51
00 47
Other 2
1.0
FIBER
15
2.9
-
1200
1200 (tr)
1540
4.5
SILAHIZED
FORM
AVAILABLE
FRABKUH
FIBER
CERTAIN
TEED
CaSO*
WISKERS
*
0.8
FIBER
SO*
2
25+
3.0
300 KPSI
1800
2100 (tr)
2600
~3.5
SLIGHTLY
SOLUBLE IN
WATER 0.1 g>
GRAPHITE
UFA
UHIOB CARBIDE
99.5Z C
98.9
FIBER
6350+
8.4
750*
1.4
120 KPSI
1200
-1.0
CARBOR
WFA
UHIOH CARBIDE)
912 C
29.6
FIBER
6350*
11
575+
1.4
30 KPSI
1000
-1.0
SOLKA-FLOC
BROWR CO.
CELLULOSE
1.2
FIBROUS
76
18
4
1.4
-
-400
1.0
5.7X
MOISTURE
KEVLAR 29
DUPONT
AROMATIC
POLUHIDB
1007. ORGANIC
19.8
FIBER
6350*
15
423+
1.45
400 KPSI
700
800
1.0
STEEL FIBER
AMERICA!!
STEEL WOOL
SAB 1010
C 0.1
Mn 0.4
S 0.1
Fe 99.4
2.7
FIBER
800-2000
80-100
10+
-
~1000 F
~2SOO F
5.5
•Fibril Dloettr
"Relative to ubeitoi.
-------
the health and safety implication of the substitute fiber system. After con-
siderable study of existing information, Bendix has chosen substitute materials
which, in our judgment, are free from serious health implications.
Processing Conditions
Current organic friction materials have been developed around the unique
properties of asbestos. Asbestos fiber bundles open during mixing and entrap
the friction modifiers and resin, giving a consistent mix. The compactability
of asbestos facilitates forming at room temperature with moderate pressure.
The non-asbestos fibers are much more difficult to handle. Most are very
brittle and have little or no surface adsorptivity. High bulking and segrega-
tion occur during mixing. Spring back and low tack lead to weak structures.
Combinations of additives and new processing techniques are required to over-
come these problems and produce the cohesiveness necessary for manufacturing
parts.
Performance Characteristics
The characteristics of the fibers can have significant influence on the
performance properties of the final composite. Asbestos has a high, stable
friction level, good adsorptivity for strength and wear resistance, and does
not contribute to noise.
Substitute fibers generally show greater frictional instability, little
or no surface adsorptivity, and/or significant contribution to both noise and
mating-surface degradation.
NON-ASBESTOS ORGANIC DISC PADS
Failures on Direct Substitution
A commercial Class A organic disc pad formulation, similar to one reported
earlier9 and known to contain phenolic resin, asbestos fiber, organic friction
particles (cashew and rubber dusts), zinc chips, and barytes was selected as a
baseline composition. In a series of new formulations, the asbestos fiber was
replaced with glass fiber, mica, mineral wool, Franklin fiber, a glass fiber/
mica mixture, a glass/Fiberfrax/graphite fiber mixture, and a glass/Wollastonite
fiber mixture.
The composites were run on an inertial dynamometer equipped with a Bendix-
designed Series III disc brake loaded to 1000 pounds. Stops from 50 mph (80
kmph) at 3.66 mpsps (12 fpsps) deceleration were run at different initial brake
temperatures up to 315°C (600°F). All fiber substitutions produced roughness
followed by poor friction. Generally, the composites were structurally inade-
quate producing tear-out and poor wear resistance, in addition to roughness
(Table 5). All formulations were considered failures. This led to the conclu-
sion that simple direct substitution of alternative fiber systems was not
practical.
18
-------
TABLE 5. DIRECT SUBSTITUTIONS AND THEIR FAILURES
Formulation
Baseline
b.c.e
d
f
g
h
Reinforcement
Asbestos
Glass
Mica
Glass/Mica
Glass/Fiberf rax/Graphite
Glass /Wollas toni te
Strength
• Strong
No defects
• Pad surface
tearout
• Pad surface
and edge
tear outs
• Weak
• Strong
• Pad surface
tearout
Performance
• Stable friction
Good wear resistance
• Erratic friction, fade, high
pad wear, and scored rotor
• Good friction, SL fade,
high pad, and rotor wear
• Poor friction, fade, and
inner pad wearout
• Roughness, fade, acceptable
pad wear, and scored rotor
• In-stop fade, acceptable
pad wear, and scored rotor
-------
Alternate Approach
A new baseline was selected with Increased reinforcement content to better
screen the following characteristics:
• processing
• strength
• performance (friction, wear, drum compatibility, and noise properties)
• cost
The initial objective was improved structural capability. A number of
formulations were made using high fiber concentration. As shown in Table 6,
the tensile strength results were very encouraging. The next step, which
proved very difficult, was attaining a proper balance of friction and wear to
go along with the strength.
Sample Dynamometer Results
A series of combinations of materials with a fixed ratio of glass fiber
and the other reinforcements was evaluated on a sample dynamometer (Table 7).
The results indicate that all of these reinforcement combinations are poor sub-
stitutes for asbestos fibers in that they exhibit poor friction, poor wear
resistance, poor friction stability, or poor rotor compatibility. However,
some clues were provided and it was possible to combine two of the formula-
tions to produce a new composite M. This material was then reformulated with
additional property modifiers in six other iterations to produce yet another
formulation S, which exhibited a high but stable friction coefficient, equiva-
lent wear resistance, and slightly poorer rotor wear resistance. At this point,
the study was transferred to full brake inertial dynamometer testing.
Inertial Dynamometer Results
The inertial dynamometer confirmed that formulation S had a higher fric-
tion level, slightly better wear resistance, and slightly poorer rotor compati-
bility than the baseline (Table 8). Approximately 40 iterations of formulation
S led to formulation AA which gave good friction with friction stability and
very good wear resistance. Further iterations (~10) led to formulation AL
which gave lower friction, poorer wear, and good rotor compatibility. In addi-
tion to inertial dynamometer tests, a series of vehicle tests was also
initiated.
Vehicle Test Results
Several formulation iterations were coupled with processing improvements.
Formulation DA was developed after approximately 50 iterations following"Formu-
lation AL. Formulation DN was developed after 13 iterations of a new-concept
material which has been patented.10 The vehicle test results (effectiveness,
fade, and recovery, in addition to wear data and noise ratings) are given in
Table 9 and were run according to a modified SAE J843c schedule. Formulation
Bendix D7180 is a Class A organic used as the baseline.
20
-------
TABLE 6. TENSILE STRENGTH DATA
Formulation
Baseline
A
B
C
u
D
E
B1
Reinforcer
- Asbestos
Glass fiber
Mineral fiber
Wollastonite
Suzorite mica
Glassa
Silanized mineral fiber
Tensile
Min.
3100
3400
600
850
850
2750
2900
strength
Avg.
4000
4800
1300
1500
1400
3500
3150
(psi)
Max.
4600
6350
1850
2350
1750
3750
3250
Deduced
content.
21
-------
TABLE 7. SAMPLE DYNAMOMETER TEST RESULTS
fO
N>
250F
Formulation
Baseline
A
F
G
H
J
K
L
M
S
Reinforcer(s)
Asbestos
Glass fiber
WOL/GF
Mica/GF
MF/GF
FRAX/GF
FF/GF
SOFL/GF
Proprietary
Proprietary
y
0.32
0.32
0.33
0.49
0.32
0.36
0.36
0.35
0.35
0.45
w*
0.002
0.005
0.004
0.004
0.004
0.009
0.003
0.002
0.002
0.002
450F
V
0.28
0.23
0.34
0.19
0.17
0.45
0.50
0.18
0.22
0.45
W
0.004
0.010
0.009
0.010
0.012
0.013
0.005
0.003
0.003
0.006
650F
v»
0.30
0.16
0.16
0.22
0.16
0.50
0.32
0.18
0.18
0.46
W
0
>0
>0
>0
>0
>0
0
>0
0
.022
.080
.040
.060
.080
.200
.016
.080
-
.018
250Rb
RF
1.00
1.31
1.16
1.08
1.37
-
1.75
-
1.20
1.04
RW
2.62
1.70
1.68
2.31
-
-
2.07
-
1.12
2.27
Rotor
Wear
0.0000
0.0003
0.0003
0.0001
0.0001
>0.0005"
0.0001
0.0000
0.0001
0.0001
All wear figures are in inches
3Rerun used to provide relative friction (RF) and relative wear (RW) trends after high temperature
operation.
-------
TABLE 8. INERTIA! DYNAMOMETER TEST RESULTS
Burn
Baseline
S
W
AA
AD
AL
LP*
380
400
400
400
420
440
'Wb
0.
0.
0.
0.
0.
0.
004
003
003
002
003
003
300F
LP
660
400
400
370
650
510
W
0.003
0.003
0.003
0.002
0.003
0.002
450F
LP "
700
300
350
340
600
580
i
-w
0.009
0.008
0.007
0.006
0.012
0.008
600F
LP
490
280
300
390
450
430
W
0.028
0.018
0.015
0.008
0.037
0.034
300F Rotor
LP W
470 0.007 0
0
- - 0
440 0.003 0
330 0.006 0
270 0.004 0
W
.0000
.0007
.0004
.0003
.0002
.0000
a
All line pressures are in psi.
All wear figures are In inches..
-------
TABLE 9. VEHICLE TEST RESULTS (1977 FULL SIZE STATION WAGON LOADED TO 5540 LBS)
K>
Fronts*
Preburnish effectiveness**
Full system
Post-burnish effectiveness**
Full system
Fronts only
First SAE fade (10 stops)**
Max
(Recovery - 10)
Second SAE fade (15 stops)**
Max
(Recovery - 10)
Post-fade effectiveness**
Full system
Fronts only
Wear (Mils)
Burnish (F/R)
Fades (F/R)
Total pads (F/R)
Total rotor
Noise ratings
Fronts
Rears
Class A organic
D7180
30 MPH 60 MPH
(48 KMPH) (97 KMPH)
500 500
600 600
1180 970
1100 Max
(410)
800 Max
(410)
600 500
900 670
6/6
42/3
48/9
0
10
10
Non-asbestos organics
DA
30 MPH 60 MPH
(48 KMPH) (97 KMPH)
440 460
520 530
1020 900
1000 Max
(380)
800 Max
(360)
450 460
960 850
11/9
33/3
44/12
1.0
8
10
DN
30 MPH 60 MPH
(48 KMPH) (97 KMPH)
440
500
620
(320)
(340)
420
700
11/6
22/2
33/8
1.5
6-8
10
400
420
620
1000
880
460
920
*A11 tests used same rears (BX4641A/H3133).
**Line pressures needed for 15 FPSPS deceleration per SAE J843C.
-------
The line pressure data show that the non-asbestos organics have higher pre-
burnish, post-burnish, and final effectiveness than the baseline, based on full-
system as well as fronts-only checks. This higher friction level and friction
stability are also demonstrated in the fade and recovery portions of the test.
Both non-asbestos organics showed poorer burnish wear resistance, and both
showed improved wear resistance during the fade and recovery portions of the
test. The rotor compatibility of both non-asbestos organics was poorer than
that of the asbestos-based baseline.
Formulation DA, which is more typical of Class A organics, showed less
loss in rotor wear than did the new-concept DN material. Both materials were
prone to be noisy.
Status
Non-asbestos organic disc pads are still in the development stage because
several problems have not yet been resolved:
• rotor compatibility
• wear durability
• noise properties
• processing
Bendix is continuing development efforts to commercialize non-asbestos,
organic disc pads.
NON-ASBESTOS ORGANIC DRUM BRAKE LININGS
Process Characteristics
Drum-brake linings require different processing characteristics than do
disc pads. When made by a wet process technique, friction materials require
a binder-wetted plastic mass with good cold flow properties. When made by a
dry process technique, they require good hot flow properties, but must first
be capable of being preformed under cold pressure conditions to develop
strength for handling purposes. Both wet and dry process types require the
capability of ultimate arcuate formation. All currently known alternate fibers
result in serious problems in these areas.
As in the case of disc pads, the direct substitution of alternate fiber in
existing asbestos formulations has been unsuccessful. Basic processibility has
been the first obstacle. The generally stiff, nonabsorptive alternate fibers
do not result in a wetted, densified mass. This precludes cold-pressure forming
into brake-lining strip configurations typical of wet process methods. In the
case of dry-process methods, the fiber stiffness is a deterrent to good physical
integrity of preforms and also leads to excessive lining cracking during bending.
In general, the alternate fiber materials do not result in a mix character which
allows them to be processed effectively by currently known techniques. The
solutions to these problems call for radically different approaches to material
25
-------
formulation and processing techniques. The new processing techniques require
substantial capital investment.
Testing and Development
With the application of suitable material and process changes, non-asbestos
type drum linings have been experimentally fabricated and tested. Hundreds of
formulations of duo-servo primary linings and secondary linings, along with
those for non-servo type brake linings, have been made. When processed satis-
factorily, these materials have been tested on sample dynamometers and inertial
dynamometers before selecting the better ones for vehicle testing. The use of
different formulations to overcome the process problems has resulted in sub-
stantially different frictional and wear characteristics which have had to be
modified to duplicate current materials more closely.
Table 10 illustrates the magnitude of some of the early problems and some
of the later results. Initial tests using very high friction combinations (A
and B) run on Vehicle 1 with-a front-brake hold-off valve, resulted in a seri-
ous duty shift with front brakes projecting greater than normal mileage, and
the rear brakes projecting short life because of their higher work load. How-
ever, when Combination A was run on Vehicle 2 (which had no front-brake hold-
off valve), the secondary lining (the same as in Combinations A and B) pro-
jected almost the minimum requirement of 15,000, although the primary gave only
7900 miles. Subsequent tests of improved combinations, particularly with
improved primary lining life, projected over 20,000 miles. Tests on Vehicle 3,
again without a front hold-off value, projected reasonably good life on Com-
binations E, F, 6, and H, with quite acceptable life on the more recently
developed Combination H. A comparison of wear projections on Combinations F
and G shows the importance of primary-secondary teaming. Both combinations
had the same primary, but with different secondaries, the life of the primary
decreased from 20,900 to 12,200 miles.
The above data illustrates that basic life and performance are achievable,
at least on certain vehicles. However, the materials noted above were prepared
by more involved, more expensive processes and are noisier than current asbestos
types, and the mating surface condition requires further improvement. Further,
the ability of these materials to withstand extended in-service usage must be
evaluated in a wide range of vehicle applications and environments.
Status
The first generation of asbestos-free drum linings is being evaluated by
some vehicle manufacturers. Bendix is continuing development efforts on further
improved materials.
ECONOMIC IMPACT
The economic impact of eliminating asbestos from automotive friction
materials is significant and includes three distinct segments:
26
-------
TABLE 10. LIFE TESTING ON VEHICLES
Front disk
Rear lining Pad life
combination* (miles)
Vehicle 1
Vehicle 2
Vehicle 3
A
B
A
C
D
E
F
G
H
59,600
44,500
31,400
33,200
27,600
31,100
34,800
28,100
21,450
Rear drum brake
• Primary
life
(miles)
3,700
6,600
7,900
20,700
28,300
17,600
20,900
12,200
32,800
Secondary
life
(miles)
8,200
5,900
14,500
26,800
20,400
15,900
16,900
18,700
27,400
*Same type front disc pads for all tests.
27
-------
1. Research and Development/New Capital Investment: Bendix has
committed, and will continue to commit, extensive funding to
both research and development efforts and to the new equipment
and facilities required to support asbestos-free friction mate-
rials. Over the last 5 years, the number of dynamometers, and
test vehicles at our Friction Materials Division has doubled,
and engineering headcount has been increased by over 60 percent.
The total engineering budget has tripled, and the share of the
budget devoted to asbestos-free product development has grown
from 13 percent in 1976 to over 71 percent for 1981. The corp-
orate research laboratories have also expended significant effort
in support of the division. Based on our current plans, Bendix
estimates that it will have committed over $25,000,000 to engi-
neering activities on asbestos-free product in the U.S. by 1985.
Capital expenditures must also be increased significantly. Over
the next 5 years, the average annual expenditure related to
asbestos-free products will be triple the historical average
annual expenditure for the entire division. Based on our cur-
rent plans, Bendix estimates that it will invest over $60,000,000
(1980 constant dollars) in new equipment and facilities for
asbestos-free products.
2. Product Cost: The basic cost of the product itself is a complex
function involving many factors. The amount and types of mate-
rials used, and the basic raw materials cost are obvious factors.
The fixed and variable costs of manufacturing can differ greatly,
based on the type of process and its complexity, production vol-
umes, labor costs, energy cost, and process yield, among other
factors. Administrative costs and handling/distribution costs
are also significant variables.
Preliminary cost estimates indicate that asbestos-free drum brake
linings may cost 20 percent to 50 percent more than current lin-
ings. Disc brake pads may cost 20 percent to 100 percent more
than current materials. These estimates are for products deliv-
ered in the original equipment market. We emphasize these are
preliminary estimates. Until parts can actually be manufactured
on production equipment in significant volumes, costing esti-
mates must be preliminary. The estimates are highly dependent
on the raw materials and processing techniques, which can vary
significantly. Moreover, research and development continues,
and future results can affect product cost.
3. Implementation Costs: As noted earlier, vehicle manufacturers
have an extensive series of stringent test requirements. Each
different vehicle configuration requires the series of tests to
ensure that the product conforms to the requirements. Since
asbestos-free materials may have some performance or property
differences from current materials, vehicle system redesign may
be necessary. We do not have sufficient information to accu-
rately estimate costs associated with the test programs. We
28
-------
would expect that each vehicle manufacturer would expend millions
of dollars, and possibly tens of millions, in converting their
product lines to asbestos-free materials. A key element is the
timing of the test programs. Expenses could be minimized by con-
verting to asbestos-free materials as part of the scheduled new
vehicle design programs, where significant brake-system testing
is already necessary.
TIMING
Friction materials development is a lengthy process. As mentioned pre-
viously, the materials themselves and their properties are the results of
optimization procedures, and the necessary testing programs are extensive.
These programs include not only testing by the friction material supplier to
develop and document the materials' capability, but also extensive testing by
the customer to ensure suitability and regulatory conformance in the particular
application.
Historical data gives us a sense for program timing. Evolutionary changes
generally require 18 to 24 months for supplier development and validation test-
ing, and 6 months manufacturing lead-time—that is a total of 3 to 4 years. An
example of such a change would be an improved organic disc pad utilizing the
same basic components (i.e., asbestos, resin, modifiers). Compared to its
predecessor, the new formulation might exhibit 15 percent better wear, improved
fade resistance, and the same friction and noise properties. Today's asbestos
organic linings are essentially the product of 40 years of evolutionary changes.
Revolutionary changes, which advance the state of the art, are more dif-
ficult to come by. It is unrealistic to put a timetable on invention, but
establishing the feasibility of a new concept can take 12 to 18 months.
Reducing that concept to a product with some or most of the basic character-
istics can take 12 to 24 months. Formulation development to obtain a balanced
set of characteristics for commercial application, and validation of those
properties requires 24 to 36 months. As before, 12 to 18 months for customer
application testing, and 6 months manufacturing lead-time are needed—that is
a total of 5*5 to 8*5 years. The semimetallic discussed previously is a good
example.
Semimetallic development began in 1962. The first low volume, special-
purpose applications occurred in 1969. General acceptance came in the mid
1970's with the second generation of semimetallic formulations. Today, semi-
metallic disc pads are utilized on the front brakes of approximately 50 percent
of the new vehicles built in the U.S., and projections approach 100 percent
utilization by 1985. It has taken continued development and improvement of
semimetallic properties to achieve this level of use.
The elimination of asbestos from automotive friction materials must be
considered a revolutionary change. There are strong indications that the
asbestos-free materials can achieve general acceptance more rapidly than semi-
metallies did. However, basic development needs demand a minimum time from
the start of a program to initial production and application. Assuming a 1975
start date, historical data would suggest that initial applications could be
29
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expected in the 1982/83 time frame, and we believe that we are close to that
timetable. However, this only applies to the first generation of asbestos-free
materials. Continued engineering effort (evolutionary changes) will be required
to develop both the second generation of materials with improved properties, and
the multiplicity of types of formulations necessary for different applications.
As indicated earlier, semimetallic disc brake linings containing no asbes-
tos in either the friction material or the backing layer are in use today. It
should be pointed out that the semimetallic friction materials have some char-
acteristics which may preclude their utilization in certain vehicle applica-
tions. An orderly transition to significantly increased utilization of semi-
metallic disc pads on new U.S. vehicles is in process, and will probably
approach 100 percent utilization no later than 1985.
Development continues on both asbestos-free organic disc-brake linings
and on semimetallic drum brake linings, but the timing for production Imple-
mentation cannot be accurately predicted.
The initial generation of asbestos-free organic drum-brake linings is in
the final development stage at Bendix, and initial evaluations are underway at
vehicle manufacturers. Some asbestos-free blocks are available commercially
for heavy truck applications. While it is too early to tell whether these
formulations will achieve commercial success, the first significant production
release would probably be in 1982.
Although this presentation has primarily addressed original equipment con-
siderations, the use of asbestos-free materials in the automotive aftennarket
will create additional challenges. As new vehicles are produced with asbestos-
free friction materials, they should be serviced with asbestos-free products.
However, since the asbestos-free materials may very well have property and
performance differences compared to current friction materials, it may not be
possible to substitute the asbestos-free materials directly in older vehicles
without compromising safety. Hence, significant time and effort will be needed
to evaluate the effect of new asbestos-free friction materials in aftermarket
applications to ensure safe and efficient braking and adequate lining life
prior to the release of these asbestos-free materials for use in the aftermarket.
SUMMARY
ji
Automotive friction materials are complex composites that have developed
around the properties of asbestos. There is no simple substitution for asbes-
tos fibers in automotive friction materials. Extensive engineering programs
are required to develop new asbestos-free formulations and process techniques,
and to conduct testing to ensure the adequacy and safety of the new friction
materials.
Semimetallic disc pads, originally developed for heavy duty applications,
meet the criteria of being asbestos-free and are in use today. The trend
toward significantly increased usage is well established. The first generation
of asbestos-free drum linings for passenger cars and light trucks is in the
final stages of development at Bendix, and in the initial stages of evaluation- by
30
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vehicle manufacturers. If these asbestos-free drum linings prove to be com-
mercially acceptable, initial limited production usage could occur as early as
1982. Some asbestos-free friction materials are currently available on the
market for heavy truck applications.
Engineering programs continue on Improved versions of the materials men-
tioned above, and also on other types of materials which might prove successful.
Bendix is committed to developing asbestos-free alternatives, and an orderly
transition to such materials is now taking place. Significant engineering
effort and time is needed to accomplish this transition.
As stated in the Bendix Corporation's 1979 annual report, "...Bendix early
in the 1980's will offer its automotive customers brakes made with long-wearing
high-performance friction materials that are asbestos-free." We intend to meet
that commitment.
REFERENCES
1. Aldrich, F. W. and M. G. Jacko. Organic Friction Materials. Bendix
Technical Journal. Vol. 2 (No. 1), 42-54. (Spring 1969.)
2. Jacko, M. G. and R. T. Ducharme. Brake and Clutch Emissions Generated
During Vehicle Operation. Society of Automotive Engineers Transac-
tions. JJ2, 1813 (1973); also SAE Paper 730548.
3. Anderson, A. £., R. L. Gealer, R. C. McCune, and J. W. Sprys.
Asbestos Emissions from Brake Dynamometer Tests. Society of Auto-
motive Engineers Transactions. 82, 1832 (1973); also SAE Paper 730549.
4. Murchio, J. C., W. C. Cooper, and A. DeLeon. Asbestos Fibers in
Ambient Air of California. Final Report. University of California
Contract ARB 4-054-1. March 1973 (also EHS Report #73-2).
5. Klein, B. W. Semimetallic Outer Pads for Disc Brakes. Bendix Tech-
nical Journal. Vol. 2 (No. 3), 109-113. (Autumn 1969.)
6. Rhee, S. K. and J. P. Kwolek. U.S. Patent 3,835,118, issued
* Sept. 19, 1974.
7. Jacko, M. G. and S. K. Rhee. Brake Linings and Clutch Facings.
Kirk-Othmer Encyclopedia of Chemical Technology. Vol. 4, 202-212,
(1978).
8. Kwolek, J. P. Friction Materials for Small Car Solid Rotor Applica-
tions. SAE Paper 750874. October 1975.
9. Jacko, M. G. Physical and Chemical Changes of Organic Disc Pads on
Service. Wear 46, 163-175 (1978).
10. Klein, B. W. and M. G. Jacko. U.S. Patent 4,175,070 issued
November 20, 1979.
31
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DISCUSSION ON FRICTION PRODUCTS
QUESTION (Chairman Guimond) : You discussed quite a bit relative to the
work that has to be done in research and development and the
cost involved in equipment. In discussing the increased costs,
that is 20 to 50 or 20 to 100 percent, depending upon what pro-
duct line you were talking about* did these increased costs re-
flect research and development in the capital equipment writeoffs?
And secondly, could we also anticipate, that as you learn more
about manufacturing that the relative costs would come down?
ANSWER (Mr. Brunhofer): As I tried to indicate in the presentation, we
separated the cost discussion into three segments. The first
was research and development and capital, and since we discussed
those costs under that topic, we felt it would not be fair to
also include amortization of those costs when we talked about
product cost; therefore, we did not include research and develop-
ment costs or capital. We simply looked at the manufacturing
process and the types of materials, as best we could identify
them, and did cost studies on the cost of the materials.
Part of the variance that we put into the discussion of increased
costs has to do with estimates on what our effectiveness will be
as the process gets started. Obviously, with semimetallic
materials, there is a significant body of knowledge available.
The variance there, as I tried to indicate, is more with respect
to what the base line material is, as opposed to any new process
development. But in the area of drum brake linings, where we
feel we are close, and in the area of semimetallic drum and sub-
stitute fiber disks, we simply do not have any method of running
production materials at this time. The capital equipment is on
order, but it is not in place, and until we get those lines
running, it is very difficult to come up with firm numbers.
QUESTION (Mr. Fenton): I am from Marietta Resources. To what extent have
you been codeveloping, or working with any of the suppliers who
may be competent or able to modify drum brake linings?
ANSWER (Mr. Brunhofer): We have worked with suppliers. We recognize
the fact that their knowledge as to treatments of materials for
our specific application can be very helpful. Other than that,
it is a source of information we have used and we will continue
to use and look forward to anything that anyone might have to
offer in that area.
32
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QUESTION (Mr. Wing): I represent Dow Chemical, which neither makes brake
linings nor any components that go into them, so my concern as a
citizen is the cost of regulation. Based upon the Bendix report,
I believe there is about one ton of airborne asbestos, produced
annually from passenger cars, and a total of about three times
that amount, scattered over an area of about 3,000 miles by 2,000
miles. I cannot conceive that that presents an unreasonable risk,
so why are we even talking about substituting asbestos?
ANSWER (Chairman Guimond): No, I would rather not get into the bad or the
good points of why we should or should not regulate asbestos at
this stage from the standpoints of a health hazard. Clearly,
there are problems with the various occupational exposures; but
nonetheless, we appreciate your comment.
QUESTION (Mr. Castleman) : I would like to know if you deal in international
as well as domestic markets, and what interest is there from
foreign automobile manufacturers and foreign governments in pro-
ducts that you talked about today?
ANSWER (Mr. Brunhofer) : In answer to your question, yes, we do deal in
international markets. Most of what I have addressed today has
to do with the business of the Friction Materials Division of
Bendix, which is the U.S. operating arm. Bendix also has divi-
sions involved in friction materials worldwide. Those divisions
also have programs with respect to friction materials in their
own market places and with their own customers.
There is international interest. For a while, the interest in
the U.S. was more intense than the interest in Europe; then for
a period of time, the interest in Europe became very intense.
There are materials under evaluation in Europe. The Japanese
have been interested.
We have tried to work with our customers (vehicle manufacturers)
to keep them informed of the situation as we see it, and that
does include not only the U.S. and U.S. auto makers but also
international markets, both as they pertain to those marketplaces
themselves and the products that may come into the U.S.
QUESTION (Mr. Castleman): At this point is the United States at the
leading edge, in commercially developing and using the substitutes
or do you find there are other countries that are in an equivalent
position today?
33
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ANSWER
QUESTION
ANSWER
(Mr. Brunhofer): I am not really an expert in that area. Just
from top-of-the-head knowledge, I would say the European market
is about even. As I understand the European market right now,
it is roughly at the state where there are products that are being
evaluated by the suppliers and by the vehicle manufacturers. I
believe in one or more of the Scandinavian countries there is
legislation that either severly limits or totally bans the use of
asbestos. I am not 100 percent positive in that area.
(Mr. Moon): I am with Jim Walter Research Corporation. I would
be interested in knowing what kind of criteria you use in looking
at substitute fibrous material? What kind of health information
do you require in evaluating substitute fibers? Is it specific
or is it general?
(Mr. Brunhofer): Some of it is rather specific; some if it is
obviously general. Primarily, we have looked at the information
available in the literature. We have worked with the suppliers.
One of the things we have special concerns about is fiber size.
We feel it is a very important issue and we have made some judg-
ments as to what size fibers we will and will not use. And that
is one of the restrictions on any fiber that we will consider.
Obviously, a second very important aspect is the capability to
withstand severe use and that eliminates many fibers. We also
have some concerns as to what is going on at the fiber surface.
We are seeing extremely high temperatures at the surface. We
wonder what the byproducts might be of some of the substitute
materials, and this is an area that I think is in its infancy.
I do not want to be more specific than that but those are some
of the considerations.
34
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GASKETS AND PACKINGS
by
Mr. Stephen D. Koehler
Greene, Tweed and Company
North Wales, Pennsylvania
ABSTRACT
ALTERNATIVES TO ASBESTOS AS A BRAIDED PACKING MATERIAL
The advantages of asbestos packings are that they are strong, inexpensive,
and are resistant to heat and chemicals. Disadvantages are that they are
very abrasive and have poor heat dissipation. Substitutes for asbestos
packings are available. To properly evaluate their performance, mechanical
(pressure, velocity), chemical (acidity, causticity), and thermal
(environmental, friction) factors must be compared to those of asbestos
packings. The costs of non-asbestos packings might seem higher than those
of asbestos packings. However, when maintenance and operating costs are
considered, the newer synthetic packings are competitive.
GASKETING
Commercially available non-asbestos gasketing materials include vegetable
fiber, cork composition, plastics, rubber, graphite, beater-saturation
materials, and metals. Performance characteristics.of these materials
are discussed and compared with those of asbestos-containing gaskets.
ASBESTOS AS A BRAIDED PACKING MATERIAL AND ALTERNATIVES
Asbestos yarns are the most common materials used in the manufacture
of braided and woven packing materials, used as sealing devices in fluid
processing and fluid power equipment. Braided packings are technically
compression packings, because of the manner in which they perform, the
sealing function. Made from relatively soft, pliant materials, compression
of Jam packings consist of a number of rings which are inserted into the
annular space (stuffing box) between the rotating member and the body of
the pump or valve. By tightening a follower or packing gland against the
top ring, pressure is transmitted to the packing set, expanding the rings
radially against the side of the stuffing box and rotating member,
effecting a seal.
35
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Compression packings find their major uses in the process industries
such as petro-chemical, paper and steel mills, and in services such as
utilities, marine, water, sewage, food and nuclear power. They seal all
types of fluids-water, steam, acids, caustics, solvents, gases, oil, gasoline
and other chemicals—over a broad range of temperature and pressure con-
ditions. They are used in rotary, centrifugal and reciprocating pumps,
valves, expansion joints, soot blowers and many other types of mechanical
equipment. There are dozens of manufacturers of compression packings and
thousands of marketing outlets, when you consider the fact that the
majority of compression packings are sold through local industrial
distributors.
Compression packings are made up of two or three components. The most
important component is the yarn, which is made up of fibers or filaments
spun together to produce a material which can be braided to form the body
of the packing. This yarn gives the packing shape and is the strength
member of the packing. Asbestos is the most common base material of which
yarn is made for braided packings. The other two components are the
suspensoid which fills the interstices in the braid and acts as a blocking
agent, and the lubricant which reduces the frictional drag of the body
materials on the shaft, to reduce heat build-up and energy requirements to
operate the pump.
Asbestos has been used as a body material for compression packings for
four main reasons. First of all, it is a very strong material. It can
withstand the mechanical beating and abrasive attack found within the stuff-
ing box area of a pump. Second, it is highly resistant to chemical attack,
holding up to fluids from pH of 2-14. Thirdly, it is temperature resistant.
AAAA asbestos can withstand temperatures up to 1000F. Fourth, and probably
the most important reason for its use today, is that it is a relatively
cheap material. Raw asbestos yarn sells for less than $2.00 per pound, when
purchased in large quantities.
The disadvantages of asbestos, from an application engineer's stand-
point, are as great as the advantages. Asbestos is a mineral, mined from
the ground in rock form. To get it to packing yarn form, the asbestos fiber
is spun around a carrier filament such as cotton or TFE. Asbestos fiber is
very abrasive, acting much like a grinding wheel, when the yarn is
compressed against a rotating shaft (as in a stuffing box). The suspensoid
and break-in lubricant protect the shaft for awhile, but eventually the raw
asbestos contacts the shaft or sleeve, causing scoring and eventual de-
struction of the component with which it comes in contact. Unfortunately,
this process is often aided by the untrained maintenance man, who over-
tightens the packing gland, to reduce the pump drippage. As he does this,
heat builds up, because of frictional drag. We are all familiar with
asbestos as an insulator, basically to hold the heat in or out of our houses.
The same thing happens within the stuffing box—with disastrous results.
The trapped frictional heat boils all the lubricant and suspensoids out of
the packing. The built up heat then has no place to go but along the shaft,
eventually overheating the bearings, causing a failure and shutdown of the
whole pump for major repairs. To keep this from happening, all packing
36
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manufacturers and pump manufacturers recommend a fairly generous flow of
pumpage to be allowed to leak past the asbestos packings, to provide a
cooling flow, and also a fluid film for the packing to ride on rather than
the metal surface of the shaft. In some cases, an outside source of cooling
and lubricating fluid is injected into the stuffing box area, through a
porous ring called a lantern ring.
In spite of the problems just described, a well-trained maintenance
crew could get reasonable life out of a set of packing, or what they thought
was reasonable life because they had nothing with which to compare. In the
1950's, the development of teflon, by DuPont, began the era of the synthetic
packing yarn. Teflon covered a wide range of applications with a pH range of
1-14, temperatures up to 500 F, and shaft speeds up to 1200 FPM. Its heat
dissipation is poor, and not only that, it expands when heated at a rate
ten times higher than the metal around it. So for a different reason we
get the same mode of failure. In the 60 *s and 70* s, other synthetic packings
were developed, the state-of-the-art now being the carbonaceous fiber packings.
Table 1 outlines the most important packing fibers in use today, showing
their advantages, disadvantages, and most common usage. TFE impregnated
Aramid fiber is becoming the most pjpular asbestos substitute for service
within the pH range of 3-11, for temperatures up to 500°F, and for shaft
speeds under 2000 FPM. Its strength and non-contaminating qualities account
for its popularity in such industries as pulp and paper and waste water
treatment. Another popular packing fiber is Graphite/TFE composite. Its
wider pH range of 1-14, and greater heat dissipation, makes it more versatile
than Aramid or pure teflon. Its only drawback is its color, which is gray,
causing some concern where color contamination could be a problem. The
carbonaceous fiber packings, as stated above, are the first choice for all-
around service superiority. They cover almost any process fluid, except for
the very volatile strong oxidizers, such as oleum, fuming nitric acid, aqua
regia and fluorine. For this reason, these products are approaching truly
"universal packing" status, and once their usage becomes widespread, the
economics of scale will bring their costs within the range of the synthetics
which preceded them.
Performance of Asbestos Substitutes
In the selection of a dynamic service packing, two important criteria
are the PV and the pH factors.
The PV factor, which is the factor for mechanical conditions, is
determined by multiplying the pressure on the stuffing box by the velocity
of the shaft. The resultant PV factor will pinpoint a range of applicable
packings .
PV Factor = Pressure on stuffing box (PSI) multiplied by
velocity of shaft (FPM)
PV = 2/3 discharge pressure x x Shaft Diameter x 3.14)
37
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TABLE 1. FIBER USAGE CHART
Fiber
Advantages
Disadvantages
Most common usage
00
Asbestos Heat resistant, pressure resis-
tant, strong (tear resistance),
availability, price.
Aramid Super strong, tear resistant,
flexible, lowest priced
synthetic fiber, non-staining,
long service life.
Graphite/TFE Reduces run in time, chemical
Composite resistant, low thermal expan-
sion, nonscoring, good heat
dissipation, light weight
(more feet/lb), not messy,
nonstaining, flexible, will
not extrude, a product you
can standardize on. Great
in valves, long service life.
TFE Low friction, chemical resis-
tance, nonstaining.
Carbon Heat dissipition, takes high
shaft speeds, least expensive
in the carbon/graphite family,
temperature resistant to
1200"F, operated with a lower
drip rate, repack costs
reduced total,removal not
always necessary.
Graphite Heat resistant, heat dissipa-
tion, fastest shaft speed,
chemical resistance, long
service life, light weight,
near zero thermal expansion,
near zero drip rate, a viable
alternative to the mechanical
seal, will not harden.
Heat insulator, abrasive,
health hazard, messy, low
service life, fluid
compatibility.
Hard to cut, cannot be die
formed, 3-11 pH range 500
temp, limit.
If over tightened, it may
glaze, possibly price.
Thermal exoansion, low shaft
speed, SOO°F limit, possible
price.
Brittle, possibly price.
Brittle, frays, price.
Depending on braid and lube:
General service pumps, valves,
etc.
Papermill-stock pumps hydro-
finers, etc., sewage treatment
plants-centrifugal sludee pumps,
etc., all slurries in the 3-11 pH
range. Possible future to
replace all TFE/Asbestos.
Chemical pumps, especially effec-
tive on chemical slurries,
sewage/slurries, general service.
Chemical pumps and valves,
food and drug pumps and valves,
nonstaining applications.
The best boiler feed pump
packing going especially the
large ones in power plants,
chemical pumps, boiler recircu-
lating pumps, this is a good
general power plant packing.
In the dry form it is used in
high temperature valves in power
plants, high speed-low drip
rate pumps, very hot chemicals,
chlorine agitators, exotic high
temperature and highly corrosive
materials.
-------
The Fluid Sealing Association has developed a chart showing this range,
and it has been reproduced in this treatise as Table 2.
The pH factor is a numerical measurement of the intensity of severity
of an acidic or caustic solution. This is the measurement of chemical attack
which a packing will encounter. Tables 3 and 4 cover the pH values, and
shows which packings are applicable to a specific pH factor.
The third criteria, equally important as the first two, is resistance
to temperature. Aramid, Teflon and Graphite/TFE composites are generally
limited to 500°F. Carbon Yarn is rated to 1200°F in steam or 650°F in
oxidizing atmospheres. Pure Graphite goes all the way up to 6000°F in non-
oxidizing atmospheres, 1200°F in steam, and 800°F in oxidizing atmospheres.
An important factor to consider as far as temperature goes is frictional
heat. If the surrounding atmosphere in which the packing must perform is
close to the temperature limit of the packing (within 75-100°F) , then care-
ful attention must be paid to proper break-in of the packing, and maintaining
adequate drip rates to enhance cooling and heat transfer away from the packing
and delicate pump components. Even though packing materials such as graphite
could withstand the heat, the crystalline structure of the metallic pump
components could be altered, causing degradation and failure, or else oil
seals and bearings may succumb'to the heightened temperatures, also causing
shutdown for major overhaul.
Table 5 represents an attempt to compare the various packing materials
discussed in this treatise in some meaningful, practical way. It is titled
"Experimental Preference Rating Chart", because the ratings are based on our
experience in the field, and take into account more than just the three
factors discussed previously. We have set up hypothetical examples of
applications which could be found in almost any of the process industries.
Service life of the packing, efficiency of energy usage, and equipment life
are the three criteria which we give an experimental rating. One hundred
is the highest a product can be rated and zero is the lowest a product can
be rated.
The Economics of Change Over to Asbestos-Free Braided Packing
Braided packings are sold to the MRO user directly by the manufacturer
and through industrial distributors on a per pound basis. Table 6 shows
the comparative cost per pound of the most often used packing materials, in
a ready to use braided form. Graphited and TFE impregnated asbestos re-
present probably 60-80 percent, in poundage, of all the heavy duty packings
sold today. Even though braided packings are sold on a per pound basis, to
understand the cost of using a specific packing, it is more relevant to talk
about costs per packed stuffing box. Table 7 gives us this comparison.
Studying these charts, it would seem that there will be some economic
hardship for the user to switch over to the asbestos-free packings. The
truth is, that when all the costs are taken into account, the non-asbestos
packing becomes the most cost effective alternative. The examples shown on
Table 8 very clearly show that because of the superior life characteristics,
39
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TABLE 2. PV FACTORS
Surface
velocity,
Pressure FPM PV factor
0-50 PSI 52-916 45,800
51-100 PSI 916-1885 188,500
101-174 PSI 916-1885 328,000
175-250 PSI 916-1885 471,300
Stuffing box
temp., "7 Aramid
50-150 X
151-500 X
501-600
601-750
50-150 X
151-500 X
501-600
601-750
50-150 X
151-500 X
501-600
601-750
50-150
151-500
501-600
601-750
Graphite /TFE
Carbonaceous TFE composite
X X
X X
X
X
X X
X X
X
X
X X
X X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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TABLE 3. pH VALUES
14 Very severe caustic
13
12 Severe caustic
11
10
9 Mild caustic
8
7 Neutral (distilled water)
6
5 Mild acid
4
3
2 Severe acid
1
0 Very severe acid
The pH factor is a numerical measurement of the intensity
of severity of an acidic or caustic solution. In addition,
the degree of concentration of the pump fluid will effect
packing selection, and it also must be taken into con-
sideration. From Table 3 you can select the materials
which are suited to the pH value of the fluid.
41
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TABLE 4. pH FACTOR DETERMINES CORRECT
PACKING MATERIALS
pH Applicable packing
range materials
0-1 TFE Fiber
Carbonaceous Fiber
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
2-3 TFE Fiber
Carbonaceous Fiber
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
4-5 TFE Fiber
Carbonaceous Fiber
Aramid TFE-Dispersion
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
6-7 TFE Fiber
Carbonaceous Fiber
Graphite Tape
Cellulostic
Aramid TFE-Dispersion
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
8-9 TFE Fiber
Carbonaceous Fiber
Cellulostic
Aramid TFE-Dispersion
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
10-11 TFE Fiber
Carbonaceous Fiber
Aramid TFE-Dispersion
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
(continued)
42
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TABLE 4 (continued)
pH Applicable packing
range materials
12-13 TFE Fiber
Carbonaceous Fiber
Graphite Tape
Graphite/PTFE Composite
FTFE Impregnated Carbon
14 TFE Fiber
Carbonaceous Fiber
Graphite Tape
Graphite/PTFE Composite
PTFE Impregnated Carbon
43
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TABLE 5. EXPERIMENTAL PREFERENCE RATING CHART
Application data
Service 1
Service 2
Service 3
Motion
Fluid
Temperature
Shaft speed
Discharge pressure
Drip rate
Flush
Rotary
Clear, neutral
200°F
800 FPM
50 PSI
100 drops/tnin
No
Rotary
slurry, pH 6-8
200°F
800 FPM
50 PSI
100 drops/min.
Yes
Rotary
Acid slurry, pH 2
400°F
2000 FPM
150 PSI
20 drops/min
Yes
Service life
Energy use
Equipment life
Service life
Energy use
Equipment life
Service life
Energy use
Equipment life
Service life
Energy use
Equipment life
Service life
Energy use
Equipment life
Service life
Energy use
Equipment life
Asbestos
40
10
5
Aramid
60
60
70
Graphite/TFE
composite
90
80
80
Teflon
90
90
60
Carbon
95
90
90
Graphite
100
100
100
Asbestos
40
10
5
Aramid
100
60
70
Graphite/TFE
composite
90
80
80
Teflon
90
90
60
Carbon
95
90
90
Graphite
100
100
100
Asbestos
10
10
5
Aramid
10
60
70
Graphite/TFE
composite
100
80
80
Teflon
25
90
40
Carbon
95
90
90
Graphite
100
100
100
Note: 100 = Highest efficiency
50 = Satisfactory
30 = Unsatisfactory
44
-------
TABLE 6. BRAIDED PACKINGS USER COST/LB
The following chart is based on a 1 Ib
unit of interbraided packing material.
The packing cross-section (square) is
3/8".
Material Cost/lb*
Flax $ 9.50
Cotton 9.60
Graph!ted asbestos 13.50
TFE impregnated asbestos 23.00
Aramid 37.50
PTFE 61.00
PTFE/Graphite 69.50
Carbon 111.50
Graphite 170.50
*Cost/lb is based on an average user list
price of four major suppliers. Actual
cost may vary due to quantity buying or
other variable factors.
-------
JS
ON
TABLE 7. BRAIDED PACKINGS COST PER PACKED STUFFING BOX
The following chart is based on packing a pump, valve, mixer or similar rotating shaft
driven component. The sealing rings are located in a housing called a stuffing box.
Our model for this chart requires five sealing rings per stuffing box. The packing is
braided interbraided style, and is 3/8" square cross-section. Costs shown are based
in industry norms, and could vary with different suppliers.
Shaft
diameter
1"
IV
2"
2V
3"
3V
4"
Oraphited
asbestos
$2.68
3.52
4.65
5.64
6.48
7.61
8.60
TFE/Impreg.
asbestos
$ 4.29
5.72
7.36
9.00
10.43
12.57
13.50
TFE impreg.
aramid
$ 6.45
8.60
11.11
13.62
15.77
18.28
20.43
TFE/Graphite
composite
$10.50
13.78
17.72
22.31
25.59
29.53
32.81
Graphite impreg.
carbon
$12.00
16.80
21.60
26.40
31.20
36.00
39.60
Shaft TFE impreg. Graphite impreg.
diameter
1"
IV
2"
2V
3"
3W
4"
TFE
$13.06
17.42
22.86
27.76
32.12
37.57
41.92
graphite
$21.17
28.87
36.57
46.20
53.90
61.60
69.30
-------
TABLE 8. ONE YEAR TYPICAL OPERATING/MAINTENANCE COSTS
PACKING A PUMP WITH ASBESTOS BRAIDED PACKINGS
VERSUS SYNTHETIC PACKINGS
1.
2.
3.
4.
5.
Economic factor
Expected packing life
Packing set costs (1)
Labor to repack (2)
Sleeve replacement
Energy consumption (3)
Total
Graphited
asbestos
4 months
$ 13.95
90.00
300.00
480.00
$883.95
Graphite/TFE
composite
12 months
$ 17.72
30.00
00.00
384.00
$431.72
Minimum 1 year savings per packed pump by using non-
asbestos packing is $452.23.
Other variable cost factors inherent with continued
usage of asbestos packings:
1. Downtime costs while repacking glands and/or
replacing sleeves.
2. Downtime costs, labor costs, parts costs to
replace bearings damaged due to heat build-up
caused by high friction and poor heat dissipa-
tion qualities of asbestos packings.
3. Product loss necessitated by high drip rates.
Also clean up and housekeeping costs.
NOTES: (1) Based on 2" diameter shaft, 3/8" cross-
section packing 5 rings per set.
(2) Based on 2 men, 1 hour per repack, $15.00
per man hour.
(3) Based on 2 kw/hr for pump packed with
asbestos, 1.6 kw/hr for pump packed with
synthetic packing. (Assuming 20 percent
differential due to friction, actual
differential will be greater), 4000
operating hours per year.
47
-------
lower friction, and non-abrasiveness of the alternatives, non-asbestos packing
should be the first choice of packing users, irrespective of the other prob-
lems associated with asbestos usage.
The packings industry has for many years been marketing and recommending
asbestos-free packings as the most cost effective seals for all types of
rotating equipment. Original equipment manufacturers and maintenance personnel
have resisted this movement, mainly for economic reasons. Much time and
money has been spent educating these two packing users on the benefits of the
asbestos-free alternatives. The major cost then, to the manufacturer of braided
packings is not in capital equipment, but in training sales and engineering
people to overcome the resistance to changing over to non-asbestos packings
because of the lack of understanding of the problems of asbestos usage.
What Effect will the Change-Over to Asbestos-Free Materials Have on
the Packings Industry?
The packings industry will be very happy to see the day when there is
a total change-over to asbestos-free packings. There are various reasons for
this.
First, it is in our, and our customers, best interest to supply the best
product for a given application. When asbestos packings were invented and
developed, they were the best product then available. Asbestos packings have
been used for so long, that they have become the standard. The newer synthetic
packings have capabilities which make them much preferable. The resistance
to their usage, based on ignorance of the over-all operating costs of
utilizing asbestos packings, will eventually be overcome, but it is costing
both the manufacturer of packings and the user money, in the meantime.
Second, because the synthetic fibers can be applied in every application,
elimination of asbestos as a packing material will allow us to concentrate
our resources on fewer products, allowing us to stock a better range of sizes,
while at the same time cutting our costs for advertising and training. We
will be able to make more efficient usage of our braiding equipment and labor,
as we do not have to set-up for asbestos any longer. We will have less
expenditures for housekeeping and monitoring equipment to ensure our workers
safety.
Finally, we can eliminate the danger of future legal entanglements, and
the drain on our resources which accompany such involvement. Any manufacturer
that has had any asbestos in any of its products is subject to enjoinment
in class action suits, and this has us constantly looking over our shoulder.
The sooner that the pump manufacturer, and the pump operator, is forced to go
to alternative packings materials the better.
GASKETING
Back in the days of the Roman Empire, a system of aqueducts was con-
structed to carry water from distant points to the cities. Some sort of
material was required to provide a seal between pipe sections since
48
-------
surfaces smooth enough to seal against each other could not be manufactured.
The Romans in many instances decided upon flax rope that had been dipped
in animal fat, as a very workable solution - and to our knowledge the first
recorded instance of gasket use.
Through the years as process temperatures and pressures began to rise,
and more reactive fluids came into use, better and better materials had to
be found. One of the best turned out to be the combination of long asbestos
fibers and high temperature rubbers. Put together with the asbestos serving
as the strength member and heat resisting material, and the rubber as the
binder and sealing material, gaskets cut from compressed asbestos sheet
have found extensive use in virtually every plant in the world.
Even in temperatures well in excess of the char point of the rubber
binder, compressed asbestos will still provide a seal. The remains of the
rubber and the filler are held in place by the thick matrix of the long
asbestos fibers and the axial pressure exerted by a tightly bolted pair
of flanges. And at moderate temperatures between a good pair of flanges,
pressures in excess of 2500 psi have easily been sealed.
The Asbestos Problem and the Alternatives
Today, with the health hazard of asbestos becoming well known, manu-
facturers have been hard at work in an attempt to develop gasketing mate-
rials that would offer physical and chemical characteristics similar to
those of compressed asbestos. Some of the materials currently commercially
available are: vegetable fibre, cork composition, cork/rubber, plastics,
beater-saturation materials and metal.
Vegetable Fibre Sheet—
Made of plant fibers and a binder, it is mostly used for solvents, fuels,
air, gases and refrigerants with temperatures to 250°F.
Cork Composition—
Produced from ground cork granules and protein or synthetic binders;
cork is used where light bolt loading is a must (glass and ceramics for
example) in water, lubricating oils and petroleum derivatives to 250°F.
Plastics—
Of all the plastics, one has emerged as the most common: PTFE. PTFE
can be used in virtually all fluids to 500°F, but in its virgin state can
creep (cold flow) under flange loading. Thus PTFE is commonly found loaded
with glass or carbon fibers to reduce creep relaxation.
Expanded PTFE—
A micro-porous PTFE structure, expanded PTFE offers high tensile
strength, virtually no significant cold flow and extremely high compress-
ibility. Coupled with PTFE's legendary fluid resistance and wide.
temperature capability (-450°F to 600°F), this material is one of the most
significant replacements for compressed asbestos gaskets now on the market.
49
-------
Rubber—
Both natural and synthetic rubbers are used, with or without a strength
member of woven wire or cloth. Normally sheet rubber gasketing is manu-
factured in a durometer (hardness) from 55 to 80 (Shore A) and varies in
thickness from 1/32" to 1/4". See Tables 9, 10, and 11 for the various
properties of each rubber.
Graphite—
Manufactured of pure graphite, this material is available with or
without wire reinforcement in thicknesses from .030" to .120" and up to
26" x 26" in size. Suitable for use in most fluids to 3000°C.
Beater-Saturation Materials—
Manufactured using a process similar to that of making paper (where the
binder is deposited uniformly over the individual fibres while suspended in
water), these materials can replace compressed asbestos sheet in most of the
same fluids although with temperature limits in the area of 350 to 500°F.
(Note: much of the research on asbestos sheet replacements falls into this
area.)
Metal--
When very high temperatures and/or pressures are encountered, spiral-
wound gaskets are normally specified. Manufactured of continuous vee-
shaped metal strip wound radially with a soft high temperature material
between each layer, they can be designed for most applications.
The Mechanics of Gasketing
Simply put, a gasket is used to create a static seal between two
stationary members of a mechanical assembly confining a liquid or gas
under vacuum or pressure. While complex formulas are used to determine
gasket design and material selection, a few simple rules can provide the
user with enough information to properly select the right gasket most of the
time.
Figure 1 illustrates the static forces acting upon a gasket.
In addition to the static forces, 3 other factors affect gasket
material selection:
1. Temperature: As temperature increases or decreases, metals
expand or contract. This affects bolt loading and can cause
softening of the gasket (creep relaxation) or burn-out of
the binders.
2. Medium: Highly reactive fluids (acids, caustics, plastics,
solvents, etc.) readily attack many binders, thus care must
be taken in specifying the correct material with each fluid.
3. General Conditions: The type of flange (see Figure 2), the
surface finish (where the surface may range from a rough
50
-------
TABLE 9. RUBBER PRODUCTS
New ASTM
reference
Features of the more commonly used
elastomers in gasketing materials
BUNA-S OR GRS SBR Good mechanical properties; economical; extensively seen as the common
"red rubber" sheet for gasketing, or as most common binder material in
compressed asbestos sheet. Suitable for hot and cold water, air, steam,
some mild acids. An all rubber SBR sheet is generally not recommended for
oils, solvents nor in aggressive type applications, i.e., ketones,
esters, etc.
Heoprene CR Excellent oil resistance; low permeability to gases; suited for nonaromatic
gasoline and petroleum solvents; highly resistant to ozone, sunlight,
weather, aging. Will not propagate flame.- Used widely in automotive,
aircraft, refrigerant type requirements.
A more expensive elastomer than SBR. Limited resistance to chlorinated
and aromatic solvents such as carbon tetrachloride, benzol, lacquer solvents.
Nitrile or NBR Superior to Neoprene in resistance to oils and solvents, aromatic and
BUNA-N aliphatic hydrocarbons, animal fats, carbon tetrachloride, lacquer solvents.
Has higher temperature resistance than SBR or Neoprene.
Limited resistance against amines, ketones, esters, ethers and some organic
acids.
Natural or NR Primarily employed as gasketing in all rubber sheet form. Properties:
Synthetic IR exceptional elongation; excellent tear strength; good wear resistance; low
Natural permanent set; recovers well; resists most inorganic salts, ammonia, mild
acids and alkalies.
Has poor resistance to oils and solvents and many chemicals and not recom-
mended where exposure to ozone, oxygen or sunlight.
Sillcone SI Outstanding elastomer for extremely high and low temperatures (-160°F to
400°F); excellent resistance to oxidation, ozone, sunlight, heat aging.
Has fair resistance to oil and gasoline but poor resistance to aliphatic
and aromatic hydrocarbons. Ordinarily furnished In rubber sheet form only.
Fluorocarbon CFM Excellent resistance to acids, aliphatic and aromatic hydrocarbons, oils,
FVSI gasoline and many corrosive industrial applications. High temperature
FPM ' limits similar to silicone, but limited in cold applications below - 40°F.
Exhibits very low permeability to gases. Ordinarily furnished in rubber
sheet form only.
-------
TABLE 10. ELASTOMER COMPARISON CHART'
Oi
Common or
trade name
Natural
Synthetic
Natural
Neoprene
SBR
NBR (nitrile)
Butyl
Chlorobutyl
Butadiene
Thiokol
BPR
EPDM
Hypalon
Silicone
Urethane
Viton
Acrylics
Hydrin
Chemical
designation
Natural
Polyisoprene
Synthetic
Polyisoprene
Chloroprene
Styrene- Butadiene
Acrylonitrile
Butadiene
Isobutylene
Isoprene
Chloroisobutylene
Isoprene
Polybutadiene
Stereo-specific
Poly alky lenesul fide
Ethylene-Propylene
Ethylene-
Propylenediene
Chlorosulfonated
Polyethylene
Polydlmethylsiloxane
Polyester
Urethanes
Fluorinated
Hydrocarbon
Polyacrylate
Epichlorohydrin
Heat
resist.
5
5
4
5
4
3
3
5
4
2
3
3
2
5
1
2
3
Oil
resist.
5
5
3
5
2
4
4
4
1
5
5
2
5
2
2
3
1
Ketone/
ester
resist.
3
3
5
3
4
2
2
3
1
2
2
4
4
3
5
5
3
Ozone
resist.
5
5
3
5
4
2
2
5
2
1
1
2
1
2
2
5
1
Low tem-
perature
resist.
4
4
4
4
4
4
4
4
4
3
3
4
1
2
5
5
2
Abrasion
resist.
2
2
2
3
3
2
3
2
4
3
2
3
5
1
3
3
2
Flame
resist.
5
5
1
5
5
5
4
5
5
5
5
2
5
4
2
5
4
Gas
perm.
4
4
2
3
3
1
1
3
2
3
3
1
5
3
2
3
1
"Numerically rated from 1 to 5 Indicating comparative suitability for a given property; i.e., "l"-most resistant,
"5''-least resistant.
-------
TABLE 11. EFFECTS OF NUCLEAR RADIATION ON RUBBER
Property effected
NR
SBR
NBR
CR OR GR
Tensile
strength
retention
3
2
1 best
4
Resistance to
decrease in
elongation
1 best
2
3
4
Retention
of elastic
modulus
1 best
2
3
4
Retention
of dynamic
modulus
1 best
2
3
4
Resistance
to
abrasion
3
2
1 best
4
The numbers in this chart are numerically rated from 1 to 4 indicating
comparative suitability for a given priority; i.e., "1" Best.
Note: NR - Natural Rubber
SBR - Styrene Butadiene Rubber
NBR - Nitrile Butadiene Rubber
CR or GR - Chloroprene Rubber
Ref: W.J. Born
B.J. Goodrich
-------
Ul
BOLT
LOAD
HYDROSTATIC
END FORCE
GASKET
BLOW OUT PRESSURE
Figure 1. Static forces acting upon a gasket.
-------
Ul
JL Ji. JL
FLAT FACE MALE 8 FEMALE, LG MALE 8 FEMALE, SM
JL JL JL
RAIS€D FACE TONGUE - 8 - GROOVE , LG TONGUE-8 - GROOVE, SM
JLJLJL
METAL-TO-METAL METAL-TO•METAL RING-GASKET JOINT
Figure 2. Flange facing types.
-------
casting to a lapped finish - also see Figure 3) and the
number and spacing of the bolts.
As the bolts are tightened, the gasket is compressed and flows into the
surface imperfections so that no pathway for leakage remains. Only the
surface does the actual sealing. The body of the gasket provides its
elastic, resilient properties (density is critical to the flow-through of
fluids). As fluid contacts the inner edges of the gasket, in many cases
the gasket will swell - increasing its sealing properties; although too
much swell signals degradation of the material itself. One final note.
The thinner the gasket, the better. But with thin gaskets the better the
flange surface finish must be, and the better the finish, the higher the cost
of manufacture. Normal gasket thicknesses range from 1/32" to 1/8" with 1/16"
being the most popular.
In summation it appears that in the gasketing industry materials do
exist that can replace asbestos. It is also apparent that standard sheet
materials have been overlooked in many applications. Compressed asbestos
sheet gasketing use can be immediately curtailed by applying one of the
aforementioned materials. This can be done with little added expense to the
customer unless the application is over 500°F. Graphite sheet metal gaskets
can replace asbestos over 500°F but their cost will constitute a major
expenditure for plant maintenance. It is the 500°F to 1000°F area where
gasketing manufacturers are searching for cost effective substitutes.
56
-------
CONCENTRIC-SERRATED
PHONOGRAPHIC
Figure 3. Types of surface finish.
57
-------
DISCUSSION ON GASKETS AND PACKINGS
QUESTION (Mr. Castleman): I would like to know if you have some data on
the amount of exposure an individual can get, trying to forcibly
remove some of these gasket and packing materials?
ANSWER (Mr. Koehler): Green Tweed does not have that particular
information. I am sure it is available from OSHA. It is not
particularly high. Based on our experience that the amount of
fiber coming off of a gasket on a flange, as it is being scraped,
probably does not create much of a health hazard. This is because
in a wet, saturated area, the fibers are contained. If the binders
are burned out and the fibers are fairly loose, it can create some-
what of a hazard. Today, you will find most plants taking
extensive precautions with masks and so forth, and roping areas
off when they have to deal with that type of problem.
58
-------
ASBESTOS IN PLASTICS: LOOKING FOR ALTERNATIVES
by
Mr. Matthew Naitove
Plastics Technology Magazine
New York, New York
ABSTRACT
Asbestos has been used as a reinforcing agent in a variety of plastics, most
notably phenolic molding compounds, vinyl asbestos floor tile, and polyester
autobody putties. In each of these areas, material suppliers and plastic
product manufacturers have been looking for alternatives to asbestos, with
varying degrees of success. This paper will summarize where asbestos is being
used in plastic and what efforts are being made to replace it.
ASBESTOS IN PLASTICS: LOOKING FOR ALTERNATIVES
Asbestos has long been considered from a technical and economic point of
view to be a valuable reinforcer/filler for plastics. However, in recent
years, the pressure of government health regulations and of a strongly neg-
ative public image that has come about with wider recognition of the hazards
of using this material have tended to discourage asbestos use in all but a
few remaining plastics applications. Given industry's successful efforts
to develop cost-effective substitutes for asbestos, as well as recently
renewed regulatory initiatives by agencies such as EPA and CPSC, asbestos
definitely appears to be on the way out of plastics, though it may take
some time before its disappearance is complete.
WHY AND WHERE ASBESTOS HAS BEEN USED IN PLASTICS
The most important functions of asbestos in plastics include enhancement
of thermal and mechanical properties, such as heat resistance, stiffness, dimen-
sional stability and impact strength, as well as improving processability
through flow control and thixotropy, plus improving economics as a result
of resin extension. (Table 1 shows some of the effects of asbestos on phy-
ical properties of plastics.)
Because of those desirable properties, asbestos has traditionally been
used in a wide variety of plastics resins—including phenolic, vinyl, epoxy,
unsaturated polyester, urea, diallyl phthalate, polypropylene, nylon and
59
-------
TABLE 1. TYPICAL CHANGES IN RESIN PROPERTIES WITH
ASBESTOS REINFORCEMENT3
Material
ABS
Nylon 6
Phenolic
Polyethylene
Polyphenylene
sulfide
Polypropylene
Polystyrene
Flexural
modulus
+130
+170
+120
+320
+60
+360
+110
%
Flexural
strength
-20
+100
+50
+30
+100
-
+5.0
change
Tensile
strength
-5
+85
-
+20
+10
-4
+20
Impact
notched
izod
-60
+20
+5
0
+100
+125
-40
HDT,
°F
+16
+200
-
+72
+35
+25
+18
gt
Optimum reinforcement usually requires 20 to 40 percent short fiber
asbestos.
Source: "Asbestos" by Robert E. Byrne, Jr., Union Carbide Corp.
brochure, reprinted by permission from the Modern Plastics
Encyclopedia, McGraw-Hill Inc.
60
-------
thermoplastic polyester (PBT). Applications have ranged from rocket parts
in military/aerospace applications to automotive brake and transmission
components, floor tiles, engine housings, bins and containers, and a variety
of coatings, adhesives, caulks, sealants and patching compounds.
This paper will concentrate on two areas that have dominated asbestos
use in plastics: phenolic molding compounds and vinyl-asbestos floor tile
(VAT). In phenolics, asbestos has been all but eliminated over the past
eight years; in VAT, the transition away from asbestos appears to be just
beginning. Virtually all other asbestos uses in plastics are believed to
be extinct, though the picture is somewhat unclear in the area of polyester
auto body fillers.
It may be noted that virtually all asbestos use in plastics involves
chrysotile asbestos. Some anthophyllite was imported from Finland in the
past, but has since become unavailable.
ASBESTOS SUBSTITUTES
Asbestos used in plastics generally costs in the range of 5-40c/lb. A
variety of naturally occurring mineral products in the same price range have
proved to be cost-effective asbestos replacements, including mica, clay talc,
clay, and wollastonite. Two of these products that are rapidly expanding their
roles in plastics filling and reinforcement are mica and wollastonite.
Mica comes in several mineral forms; however, all of them consist of
plate-like particles, which can be supplied commercially in a range of sizes
and ratios of platelet thickness to diameter.
Wollastonite is a naturally occurring calcium silicate of fibrous or
needle-like shape. Typical particle diameter is 3.5 microns and typical
aspect ratio (length/diameter) ranges from 3:1 to 20:1. It costs 3-6
-------
TABLE 2. PMF VERSUS ASBESTOS IN GENERAL-PURPOSE PHENOLIC3
Filler
Wt. %
Flex. Str. , 10 3 psi
Flex. Mod., 10 5 psi
Tens. Str. , 103 psi
Tens. Mod. , 10s psi
Notched Izod Impact
Str., ft-lb/in.
Volume Resistivity.,
10 ai ohm-cm
UL94 Flammability
(1/8 in.)
None
-
10.4
6.75
7.52
4.53
0.18
1.5
V-0
PMF
33
8.8
7.98
6.62
6.01
0.23
0.7
V-0
STb
PMF
33
12.6
10.87
8.78
5.96
0.26
1.5
V-0
Asbestos
40?
9.1
10.55
5.01
4.93
0.25
0.03
V-0
a
Data supplied by Jim Walter Resources.
Surface-treated.
Q
Commercial compound.
Source: Plastics Technology, September 1977.
62
-------
TABLE 3. PROPERTIES OF PMF-FILLED POLYMERS
Resin/FMF Z
G-P Phenolicb
0
33
33STC
50
50ST
HIPSd
0
33
50
Acetale
0
20
33
G-P PPf
0
33
50
PBT8
0 Dry
0 Wet"
33 Dry
33 Wet
33ST Dry
33ST Wet
50 Dry
50ST Dry
Nylon 661
0 Dry
0 Wet
33 Dry
33 Wet
33ST Dry
33ST Wet
Nylon 612^
0 Dry
0 Wet
33 Dry
33 Wet
33ST Dry
33ST Wet
Tens,
str.,
10s psi
-
-
-
-
-
3.9
4.4
4.1
7.6
6.9
6.2
4.9
4.5
4.1
7.3
7.0
7.8
4.6
9.5
8.5
8.2
10.8
10.3
6.9
9.3
5.5
12.7
8.7
8.6
7.3
7.3
6.0
10.8
9.0
Flex,
str.,
10 psi
13.1
9.2
13.4
8.7
12.4
_
-
-
-
-
-
-
9.5
8.3
11.8
8.7
14.5
13.2
11.9
17.2
11.4
5.9
14.7
8.9
17.7
11.4
9.4
6.3
12.4
8.7
15.0
11.2
Flex,
mod. ,
10s psi
6.62
8.23
11.58
9.38
15.55
2.97
7.50
12.00
2.80
5.50
16.00
1.56
5.50
8.10
3.30
2.83
8.15
6.45
7.84
6.02
12.80
12.70
2.04
1.80
7.80
4.30
7.30
4.30
2.98
2.12
6.63
4.33
6.42
4.67
Notched
Izod,
ft-lb/in.
0.13
0.25
0.24
0.28
0.27
1.29
0.58
0.38
1.32
0.55
0.56
0.45
0.63
0.69
0.34
0.46
0.47
0.31
0.51
0.47
0.57
0.53
0.88
1.85
0.57
0.90
0.59
1.20
0.32
0.45
0.41
0.59
0.35
0.54
Heat-distortion
temp. , F
66 psi
-
-
-
_
-
181
196
200
308
317
-
236
266
268
-
-
-
-
-
-
-
is A jSlcc
-"
-
-
-
-
-
_
386
383
386
383
264 psi
-
-
-
-
_
-
-
_
-
278
-
_
-
165
-
359
-
365
_
394
394
360
_
394
-
400
-
217
200
329
324
322
328
Avg. aspect ratio of PMF varies from 40 to 60 for the different polymers tested,
though this reportedly affects the data little.
''Durez 12763.
£
Surface treated.
dShell-324.
eCelanese M-90.
fShell P-520.
8Celanese J-105.
water conditioning: 16-hr soak of molded specimen at 122 F.
ThiPont Zytel 101.
^DuPont Zytel 151 L.
Source: Plastics Technology., April 1977.
63
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Still another synthetic product which has become important for asbestos
is glass fiber. It is being used in some new asbestos-free phenolics (see
below), and development of new sizes and types of glass fiber are expected
to increase its utility in this area, according to one phenolic supplier.
One potential drawback to glass fiber, however, is that it can significantly
increase the cost of a plastic compound relative to asbestos, though this
need not always be the case. Although glass fiber is available in many forms,
some typical grades used in plastics are priced in the range of 60-70£/lb.
One more potential asbestos replacement is presently still in the experi-
mental stages. Franklin Fiber is a crystalline calcium sulfate microfiber
with a diameter of 4-6 microns and aspect ratio around 100:1. It's produced
in pilot-plant quantities by CertainTeed Products Corporation, Elverson, PA.,
and costs 10-15C/lb. The product is slightly water soluble, and company
sources say that it is made from a non-hazardous material and does not tend
to remain in the body if ingested.
It should be noted that a considerable amount of research is being devoted
to increasing the utility of asbestos-replacement products in plastics by
treating them with silanes or other coupling agents that promote a chemical
bond between the filler and the plastic matrix. Use of such surface treatments
tends to improve both the processability and ultimate mechanical properties
of filled and reinforced compounds.
Because of the above developments, asbestos* future in plastics is in
doubt. Table 4 shows projections for total asbestos use in plastics, one
set of figures dating from 1974 and one set prepared in 1980. In 1974, the
average growth rate projected was 9%/yr; in fact, it has turned out to be
more like 7%. For the future, the latest projection is for 4.5%/yr growth,
though even this is termed "optimistic" by the source of these figures. The
remaining plastics market for asbestos is VAT, whose market curve reportedly
appears flat in the future, and will probably decline as asbestos substitutes
are found (see below).
REPLACING ASBESTOS IN PHENOLICS
About six years ago, according to one major phenolic producer, approxi-
mately 70% of all molded phenolic parts contained from 1% to 30% by weight
asbestos. At one time, 250-million Ib of phenolic compounds reportedly
contained asbestos; today, that figure is said to be 50-million Ib out of
a total market of 300-million Ib.
Asbestos-filled phenolics have been used in a number of applications
where heat resistance is required, including automobile brake and transmission
components, electrical parts, pot handles, and various knobs and other com-
ponents of large and small appliances, such as clothes washers and dryers,
dishwashers, refrigerators, portable heaters, popcorn poppers and broilers.
64
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TABLE 4. ASBESTOS USAGE IN PLASTICS
1974 Market analysis (million Ib)
Avg. annual
1971 1973 1974 1976 1984 increase '74-'84
350 405 441 523 1042 9%
1980 Market analysis (million Ib)
Avg. annual
1976 1980 1985 1990 increase '80-'90
440 518 645 803 4.5%
Source: Business Communications Co., Stamford, Connecticut.
In 1972, General Electric Company's Plastics Division was the first major
phenolic compound supplier to announce that it was completely eliminating all
use of asbestos. In 1976, another major, Durez Division of Hooker Chemicals &
Plastics Corporation said it would do the same. The company finally completed
the transition in 1979. Fiberite Corporation, which was at one time a small
factor in asbestos-filled phenolics, also eliminated asbestos use several years
ago.
Only recently has it become apparent that all remaining producers of
phenolic molding compounds intend to pursue a thorough phase-out of asbestos,
which they hope to accomplish by the end of 1980. Rogers Corporation, Reich-
hold Chemicals, Plastics Engineering Company, and Valite Division of Valentine
Sugars, Inc. all now intend to discontinue using asbestos-filled grades. Only
one smaller producer, Resinoid Engineering Corporation has said that it has
no plans at the moment to drop asbestos; rather, the company appears to be
taking a "wait-and-see" attitude regarding new proposed government regulations.
In addition, a very minor amount of asbestos-filled phenolic is being imported
from Canada.
It has taken phenolic suppliers several years of continuous evolutionary
development to arrive at a full line of asbestos replacement. At first,
there was considerable customer resistance to the new products while asbestos
grades were still available, but this customer resistance seems to have been
largely overcome. To quote a spokesman for one major phenolic supplier;
"It was a product-by-product change, using a variety of materials to develop
the same processability and end-product properties as those provided-by
asbestos. The transition was difficult. At one time, 90 percent of our
phenolic compounds contained some asbestos—today we haven't got a pound on
the premises."
65
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Although non-asbestos formulations are proprietary, and probably contain
mixtures of fillers, products such as clay, talc, wollastonite, glass fiber
and Processed Mineral Fiber are all said to have been used as asbestos re-
placements. Mica has also been evaluated in this application, but with lim-
ited success. Although mica reportedly builds stiffness much more than
equivalent loadings of asbestos, experiments reportedly showed that mica-
filled phenolics cannot be exposed to elevated temperatures for long periods
without blister formation, according to sources at a mica producer, Marietta
Resources International. However, this company reports that better property
retention is exhibited for phenolic samples containing finer grades of mica.
Today, it appears that some, if not yet all, phenolic suppliers have
been able to replace asbestos across the board with phenolic compounds that
exhibit nearly identical properties (90-98% as good, according to one supplier)
at nearly identical cost. (See Table 5.) In some cases, electrical properties
and surface appearance are said to have been improved by replacing asbestos.
There are also reports that some asbestos-free phenolic compounds flow better
for easier processing.
But there are also some trade-offs, however. In flame resistance, an
asbestos-filled grade can receive an Underwriters Laboratories UL 94V-0
rating at 0.040 in. thickness, while a non-asbestos grade may have to be 0.060
in. thick to obtain the same flammability rating. To quote a major phenolic
supplier, "We've pretty much closed our books on asbestos. We've survived
the transition in good fashion, but in our replacement products we have
sacrificed long-term heat resistance to some degree." There seems to be
some difference of opinion in industry as to whether asbestos-free phenolics
do or do not provide the same degree of long-term heat resistance. Some
suppliers say the heat resistance (retention of properties at elevated
temperature) of newer asbestos-free grades is more than adequate. But for
the very highest performance materials, confidence in asbestos replacements
may still be less than absolute.
Also, it should be noted that replacement of short-fiber asbestos has
proved easier than finding substitutes for long-fiber asbestos, which is
used in phenolics for high impact strength. Long glass fibers reportedly
can provide the same degree of impact stength, but may cost as much as 40%
more than long asbestos fibers. Long glass may also have the disadvantage
for the user in creating more machine wear than does asbestos.
ASBESTOS IN VINYL FLOOR TILE
One asbestos supplier estimates that, at one time, as much as 200-million
pounds of asbestos was used in vinyl-asbestos floor tile. This source estimates
that the figure may be slightly less now, owing to competition with VAT from
synthetic carpeting materials and non-asbestos containing types of vinyl
flooring. VAT generally contains only 10-15% by weight of asbestos. A very
short-fiber asbestos is used, costing about 5
-------
TABLE 5. GLASS FIBER VERSUS ASBESTOS IN PHENOLICS
a*
Grade
Filler
Specific Gravity
Tensile Strength, psi
Flexural Strength, psia
Flexural Modulus,
million psi
Compressive Strength,
psi
Deflection
Temperature , °F
Dielectric Strength,
V/mil Short Time
Step by Step
RX862
Glass
1.88
6,500
12,0007
14,000
2.3
28,000
500+/
550
300
250
RX865
Glass
1.88
7,500
15 ,000/
17,000
2.5
33,000
550+/
550+
300
250
RX866D
Glass
1.94
6,000
11,500
2.5
28,000
550+/
550+
290
220
RX867
Glass
1.71
6,000
11,500
1.8
27,000
450+/
500+
230
180
RX867D
Glass
1.78
6,000
11,500
2.0
28,000
500+/
550+
RX462
Asbestos
•' ' C
1.79.
6,000
12,000
2.0
24,000
500+
125
100
RX466
Asbestos
..V
« '
1.70
6,500
11,000
1.8
30,000
500+
150
100
RX468
Asbestos
1.72 ..
6,000
10,000
1.8
26,000
450
150
100
Compression molded/transfer molded.
As molded/post baked.
Source: Rogers Corp., Rogers, Connecticut.
-------
Recent conversations with two VAT producers (some refused to discuss the
subject) indicated that both are working actively to either replace asbestos
with something else or perhaps to develop a new flooring product based on
an entirely different plastic that does not require filler. Also, one pro-
ducer said it had been able to sharply reduce the asbestos content in some
of its current products, but would not explain how.
One of the two VAT producers interviewed said it hopes to be able to phase
out asbestos in the next two years, the main reason for doing so being the
bad name asbestos has acquired—consumers are becoming afraid of it anywhere.
According to this supplier, all VAT producers are working to eliminate
asbestos. "Asbestos is dead," he said.
ASBESTOS IN OTHER PLASTIC PRODUCTS
Numerous miscellaneous uses of asbestos in plastics have appeared over
the years, and some were once thought to be quite promising growth areas,
but all are thought to be defunct today. These include nylon and polypropylene
auto and appliance parts (asbestos has since been replaced by glass fiber,
mica and talc), vinyl plastisol coatings and sealants, epoxy coatings and
roofing compounds, and polyester premixes for molding auto and tractor parts,
engine housings and bins and containers. In one application where asbestos
has been used, polyester auto body putties, it's not entirely clear whether
it may still be used to any extent. Spokesmen for the Autobody Filler
Manufacturers Association (AFMA), headquartered in Chicago, assert that its
member companies do not use asbestos but also say that some non-affiliated
firms may do so. Platy talc is the approved filler, says AFMA. At least
some sources in that industry believe that there is use of asbestos or
asbestos-like materials (perhaps as a contaminant in some talcs) in some
body putties, but this could not be confirmed directly.
ACKNOWLEDGMENT
I would like to thank my associate, Assistant Editor Carl Kirkland,
for his invaluable assistance in researching this topic.
68
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DISCUSSION ON PLASTICS AND FLOORING
QUESTION (Mr. Koehler): For my own edification, I'd like to know if all
plastic products that are put out for consumer use today contain
warning labels?
ANSWER (Mr. Naitove): I am not aware of any consumer product made of
plastic containing asbestos that has a warning label. I don't
believe such a thing exists.
ANSWER (Chairman Guimond): I have seen a few manufacturers put identi-
fiers on tile and a few other products, but that is all.
69
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SINGLE-PLY ROOFING AS A SUBSTITUTE FOR
ASBESTOS ROOFING FELT
by
Mr. David E. Bailie
Koppers Company, Inc.
Pittsburgh, Pennsylvania
ABSTRACT
Asbestos has served Industry and consumers in many ways. In the roofing in-
dustry, it has solved a problem and created another. The rapid changes now
taking place in the roofing industry have presented adequate alternatives to
the use of asbestos-containing roofing felt.
Asbestos has served industry and consumers in many ways. In the roofing
industry it has solved a problem and created another.
Some of you may not be familiar with the construction of a built-up
roof, so I would like to give you a quick course on how a roof is usually
constructed.
A typical built-up roof is constructed by alternating layers of bitumen
and felt; the bitumen being either asphalt or coal tar, and the felt being
organic, asbestos, or most recently, glass.
Organic felt is in greater use, and at one time, was produced with a
high rag content. However, economics and lack of supply has caused the
producers of organic felt to go to a high paper content with a small amount
of wood fiber. Dry felt is run through a saturator that allows the dry felt
to soak up the bitumen saturant close to a point of saturation.
The bitumen used in built-up roofing is either asphalt or coal tar.
Asphalt is a derivative of petroleum and is available with various softening
points to suit the specific needs of the roofing contractor. Coal tar is
derived by the destructive distillation of coal, better understood as the
production of coke used for making steel. Both bitumens require heat to
cause the bitumen to be fluid.
71
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After the roof deck is in place, insulation is attached to the deck by
means of mechanical fasteners or a hot adhesive. The emphasis placed on con-
serving energy has increased the use of insulation and many times two layers
of insulation are applied. The felt laying begins by mopping on a prescribed
amount of bitumen into which the felt is embedded. The application progresses
from one side of the roof to the other, laying the felt in shingle-like
fashion. When a gravel surface is required, a flood coat of bitumen is poured
on the top felt and gravel is embedded while the bitumen is still hot.
Built-up roofing is very labor intensive. Modern practice utilizes
mechanical equipment to speed installation. Mechanical insulation fasteners
are driven into the insulation and deck by a drill-like device. The bitumen
is laid down with a spreader instead of a hand mop, and the felt is rolled in
behind it. On some jobs, the felt is contained on the same piece of equip-
ment. The top pour of bitumen is also laid down with this piece of equipment,
and when gravel is required, a gravel buggy is used to lay the gravel.
The success and longevity of the roof is dependent upon the homogeneous
formation of the layered construction, and you should now understand why
this type of roofing is called built-up roofing.
A built-up roof is analogous to plywood in that the layers of a roof have
little strength individually. A number 15 organic felt, for example, has aver-
age breaking strength of 30 Ibs. in its longitudinal direction and.15 Ibs. in
the transverse direction, and- can easily be torn. When the felts are laminated
with bitumen, however, the strength is substantially increased. The strength
of a built-up roof is important because of the stress induced by structural
movement and temperature fluctuations.
The degradation or weathering of a organic felt occurs when it becomes
exposed to the atmosphere. The absorption and subsequent drying of the
organic felt causes it to break down and eventually blow away. The ability
of organic felts to absorb moisture creates other problems for a roof. It
was these problems that opened the door for the use of asbestos felts in
the roofing industry.
Asbestos roofing felt became the new kid on the block. A better roofing
felt. One that did not absorb water and rot away. A roofing felt that had
better fire resistance. Indeed, a premium roofing felt to produce a premium
roof. And, I might add, at a premium price. Currently, asbestos felt is
priced at approximately twice the price of organic felt.
Asbestos felt entered the roofing industry as a substitute for organic
felt primarily for roofs that had a smooth surface, that is, without gravel
on the surface. Asbestos offered a distinct advantage on a' smooth surface
roof because this type of roof was more susceptable to degradation, and
asbestos felt would not deteriorate as would an organic felt when the top
coating of asphalt weathered and allowed moisture to penetrate. The use of
asbestos felt spread to other roofing applications as the advantages of
asbestos felt were broadcast. There is a single law that applies to every-
thing in existence — Murphy's Law. As it sometimes occurs with products that
offer advantages, there are disadvantages as well. Sometimes the disadvantages
72
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do not appear until late in the game. Such was the case with asbestos felt.
Along with the high price of asbestos felts, we have found that asbestos
felts are lacking in breaking strength. When tested as per the same ASTM
(American Society for Testing and Materials) method used to test organic felt,
asbestos possesses 1/3 less breaking strength than that of organic felt. Con-
sequently, the industry has experienced a higher rate of splitting roofs when
asbestos felts were used to build up the roof.
The use of asbestos felt for roofing has greatly diminished. There are
only two producers of such felt in the U.S. There are viable alternatives.
One such alternative is glass felts. The other is a single-ply roofing
system.
Although there have been single-ply systems existing in this country for
15-20 years, they did not blossom until the early seventies. At the present
time, the market is flooded with various single-ply systems. However, all of
them can be categorized into two groups - modified bitumen or polymeric systems.
Within those two groups lies a real variety.
Modified bitumens include systems in which the bitumen has been modified
in different ways. Some are reinforced, others are not. Some are adhered
with hot adhesive, others with a cold adhesive. And there are systems that
are not adhered at all, but instead are held down with heavy ballast.
The polymeric systems have similarities to the modified bitumen systems
in that they contain different polymers. Also, some are reinforced while
others are not. In addition, polymeric systems can also be loose-laid or
adhered. Polymeric systems include EPDM (Ethylene Propylene Diene Monomer),
Butyl, Neoprene, PVC (Polyvinylchloride), CPE (Chlorosulfonated Polyethylene),
and PIB (Polyisobutylene).
There simply is not enough time to delve into the makeup of each membrane,
nor am I qualified to adequately describe the composition of each. Each system
also has its own procedure for application, and I'll not bore you with that
either.
Instead, I would like to dwell on the two generic methods of application.
Loose-laid and adhered or semi-adhered.
Adhered systems are those that are held down with an adhesive. All
polymeric membranes use a cold adhesive, while some modified bitumen membranes
will use hot, and others use cold adhesive. The application of adhesive is
achieved simply by rolling, spraying, brushing, or mopping the adhesive onto
the surface to which the membrane is to be applied. The membrane is then
laid in place, overlapping the preceding layer. The laps are then sealed to
provide a watertight system.
The semi-adhered systems are applied by first mechanically attaching a
small piece of the membrane (9-12" square). Adhesive is then applied to these
patches which have been placed l'-2' apart. The membrane is then placed so
that the membrane is adhered only to the patches. The membrane is sealed at
the laps in the same manner as the adhered systems.
73
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The loose-laid systems are a new concept in the roofing industry. In my
opinion, it makes a great deal of sense. This method of application places
the membrane on the deck, insulation, or existing roof loosely, without any
attachment. The laps are sealed in the usual manner and heavy stone is
placed on top of the membrane to resist wind uplift. The value of this system
is that the substrate can move underneath without transmitting stress to the
roofing membrane.
In summary, I've given you a quick course in the construction of a built-
up roof, its components, the entry of asbestos felts, and an alternate to the
use of asbestos roofing felts.
In closing, I want to add that knowledgable people in the roofing industry
feel that the demise of asbestos roofing felts is imminent and asbestos felts
can, at the present, be substituted with materials of proven performance with
no economic disadvantage.
74
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ROOFING FELT
by
Ms. Nancy Roy
GCA Corporation
Bedford, Massachusetts
ABSTRACT
Asbestos provides dimensional stability, rot resistance, fire resistance, and
heat resistance to roofing felt that is impregnated with asphalt. Commercially
available substitutes include organic and fiberglass felts. Alternative pro-
ducts are compared on the basis of composition, strength, durability, product
life, cost, and length of time in the marketplace. Substitutes for asphalt-
saturated asbestos roofing felt are well-established in the roofing industry.
Installed costs of asphalt-saturated roofing felts are surprisingly close.
Labor costs for installation outweigh the costs of materials by a significant
factor.
INTRODUCTION
The following subjects: roofing felts and nonasbestos substitute products
Including organic and fiberglass felts, their composition, special qualities,
cost differentials, and length of time on the market will be discussed in this
paper. From this information, conclusions may be drawn as to the availability
and economic reality of alternatives to asbestos roofing felt.
Roofing has been a basic need ever since man first built crude shelters
to protect himself from the weather. In the past, settlers used sod and
thatched roofs as these materials were cheap and easy to come by, but they
needed to be replaced at frequent intervals, and often leaked in heavy rain
storms. At present, home and business owners are offered a wide variety of
roofing materials from which to choose, all of which fit various requirements
and contribute desired attributes to satisfy varied roofing needs.
A basic distinction can be made between roofs belonging mainly to home-
owners and large roofs on business properties. Roofers would view the dif-
ference in terms of "minimum slope" for which a roof is adapted. Whereas the
majority of homeowners' roofs are quite sloped, commercial and industrial roofs
are mainly flat. Asbestos felt underlay may be used in both instances, but
the Industrial or built-up roofs are described here.
75
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In all cases, the material discussed is used as an underlay either to other
common residential roofing systems such as asphalt shingles or classic cedar
shakes where asbestos helps prevent moisture penetration, or to asbestos felt
layers themselves in industrial built-up roofing.
ASBESTOS ROOFING FELTS
Asbestos fibers are useful in roofing felts because they provide:
• dimensional stability, and
• resistance to rot, fire, and heat.
Dimensional stability is particularly important. Given the extreme weather
conditions a roof must face, such as rapid heating and cooling of the roof
surface, cracking may occur which allows water penetration, particularly in
damper climates or in areas where snow accumulates on the roof and is then
subject to periodic melting. Asbestos roofing is considered by many roofers
to have an exceedingly long life.3*1* Rot resistance is of paramount impor-
tance on flat or nearly flat roofs with poor drainage. The fine resistance of
asbestos felt provides an extra margin of safety to property owners, and thermal
resistance enhances roof durability.
Asbestos felt sheet is manufactured with varying formulations on con-
ventional paper-making machines, then converted into roofing felt by saturation
with asphalt or coal tar. Major United States companies who have produced
asbestos roofing felt include: Johns-Manville Corporation and Celotex Corpora-
tion. Manufacturers often make the felted sheet at a centrally located site
and ship this product to geographically scattered sites for^saturation. This
saves on shipping costs as the unsaturated felt weighs less . Asbestos roofing
felt is typically composed of 85 to 87 percent asbestos fibers, 8 to 12 percent
cellulose fibers, and 3 to 5 percent starch binders . Grade 6 or 7 chrysotile
fiber imported from Canada is usually used. Other materials, such as wet and
dry strength polymers, Kraft fibers, fibrous glass, and mineral wool are often
added as fillers. The paper is made in either single or multilayered grades
and may have fiberglass filaments or wire strands embedded between paper layers
for reinforcement. The felt's thickness or grade and the amount of asphalt
costing required depend upon the product's intended use.
In built-up roofing systems, the most common type - a hot roof - often
involves the use of asbestos roofing felt. Cold roofs, not requiring the
application of hot tar or asphalt, were covered in the discussion of single-
ply membrane systems; only hot roofing systems will be considered here. They
involve the application of several plys or layers of roofing felt alternating
with asphalt or tar, often with a top layer of gravel imbedded in the asphalt.
Layers used may consist of organic, fiberglass, or asbestos felts.
Built-up roofing such as this is commonly prepared at the job site by
cutting lengths from product rolls to the required sizes and shapes. "Built-
up", as implied, refers to the practice of layering or building up paper lengths
on top of each other while hoc roofing tar is mopped between the layers for
adhesion and/or additional weather protection, having a sandwich effect. The
roofing is attached to the surface roof deck with adhesive tars (which may
76
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also contain asbestos) or by nailing If the roof can accept such treatment.
Built-up roofs can be topped with:
• gravel
• smooth, or
• mineral surfaces.
Gravel and smooth roof tops are similiarly constructed except that smooth-
surface roofs are only lightly mopped with asphalt whereas gravel surfaces are
flooded with asphalt and then covered with aggregrate gravel which generally
serves more for appearance and ballast than for true protection. In mineral
surface roofs, roofing paper is sealed with weather grade asphalt embedded
with opaque, noncombustible mineral granules giving the builder a choice of
roof colors. Asbestos roofing felt has an advantage over organic felt here
as it does not require a gravel surface, a feature which makes it easier to
inspect and repair.
Asbestos felt may also be used as an underlayer for other roofing pro-
ducts, mostly in residential applications. For this, asbestos roofing paper
is attached to the roof deck, again by tar adhesives or by nailing, then
covered with shingles, cement sheets, or other forms of common roofing. In-
cluded in this category are: metal roofs, which formerly were often galvanized
steel in corrugated sheets but now are mostly non-rusting aluminum panels;
slate roofs, an old stand-by which is now offered in imitation form offering
the hand-cut slate look at a lower cost; and tile roofs and wood shakes, both
commonly seen materials used mainly for homeowner applications. At least
60 percent of asbestos roofing felt is applied during re-roofing jobs while
the remainder is used in new construction.
ALTERNATIVE ROOFING FELTS
There are two alternatives to asbestos roofing felt other than singly-ply
membrane systems. These substitute products are organic felt and fiberglass
felt.
Organic felts have been used in United States built-up roofing systems
for about 25 years. They are made primarily from cellulosic fibers on paper-
making machines, and, as with all roofing felts, are saturated with coal tar
or asphalt. Major manufacturers of organic felts include: Johns-Manville,
Celotex, Bird and Son, Koppers Company, GAF, and CertainTeed Corporation.
Fiberglass roofing is a newer product, introduced around 1964 by Owens-
Corning, but only recently enjoying widespread use. It is composed of glass
or refractory silicate and a binder. Owens-Corning, Johns-Manville, and
others produce fiberglass felt; other companies such as PPG Industries and
Reichold Chemical Company manufacture the basic.fiberglass strand and sell
this to the actual paper product manufacturers. ' . Three basic manu-
facturing processes are employed, including the continuous filament process
used by Owens-Corning, a steam blown process using shorter fibers, and a
slurry process similar to the basic paper-making process.
77
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To compare these two products with asbestos felts, several factors
must be considered, including:
• strength and durability
• product life
• product cost, and
• length of time that the product has been available.
Although organic felt rates lowest in terms of strength and durability, it is
still the most widely used. The primary reasons are its low cost and time-
tested nature; since it has been on the market the longest, its qualities are
well known. Fiberglass products have been praised for exceptional uniformity
and natural venting characteristics. More uniform porosity of this product
allows deep penetration of asphalt leading to improved interply adhesion.
Fiberglass has the same technical features as asbestos, but requires
less asphalt saturation. Both fiberglass and asbestos systems are inorganic
and, therefore, have better rot resistance and dimensional stability than
organic systems.
ECONOMICS
A comparison of installed unit costs, which may be more meaningful, still
shows organic felt to be least expensive, but the prices are now closer. Or-
ganic felt averages about $60.00 per installed square, asbestos and fiberglass
around $70.00, and single-ply membrane at about $100.00. This is where the
single-ply membrane really shows itself to be more competitive than apparent
based only on material cost, because it is not labor intensive and material
savings (such as tar or asphalt) become evident. This should make products
like fiberglass and single-ply membrane systems become even more competitive
in the future. Industry sources believe that these materials will reduce the
share of both organic and asbestos felts in the built-up roofing market.
Lifecycle costs should also be considered: that is to say, an asbestos
roof may be slightly more expensive than an organic roof, but if the asbestos
roof is replaced every 20 years while the organic roof must be replaced every
10 years, the asbestos roof is more economical. Unfortunately, data on the
expected lifetime of the different roofing types is sparce. Lifetimes depend
on such factors as surface finish (smooth is more susceptible to degradation)
and whether coal tar or asphalt is used (coal tar lasts longer), as well as
climate and.yearly weather cycles; the roof lifetime is a difficult parameter
to predict.
A product such as Johns-Manville's Glas Fly system meets the 200 pounds
per square inch (at 0°Fahrenheit) tensile strength preliminary performance
criteria recommended by the National Bureau of Standards. This product re-
quires less mopping asphalt than other systems as more asphalt is impreg-
nated during product manufacture.
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Cost is certainly a most important aspect of substitute analysis. Specific
roofing costs are given in Table 1, attached. Two cost comparisons are valu-
able: first, basic roofing material costs for asbestos, organic and fiberglass
felts and second, the cost for installed units of roof. Since rolls come in
different sizes and the number of layers installed on the roof will vary de-
pending on the felt used, the basic unit of comparison employed is the square
- a one hundred square foot area of roofing.
In terms of material cost per completed square, only organic felt is
cheaper than asbestos, while asbestos and fiberglass are nearly equal. In
general, prices range from around $10.00 a roll for organic, to about $25.00
per roll for asbestos and fiberglass, and finally to about $65.00 for the single
ply membrane system. Prices differ from the conference hand-out figures, in
that, in most cases, they are now lower. Only the cost of asbestos has gone up.
Asbestos and fiberglass are nearly equal in quality and durability, and cost,
which is very close at present, will probably shift to favoring fiberglass in
the near future.
Since a price comparison of average costs of installed roofs only shows
about a $25 fluctuation between products, one must also look at other attri^
butes. Time-tested qualities and builder experience together with these cost
findings now become valuable in predicting market trends.
CONCLUSION
Organic felts have been marketed longer than all other roofing materials
covered, although the single-ply membrane system has been used in Europe for
a longer period than its 5-6 year introduction in the United States. Asbestos
felt is also a fairly new product in the roofing industry; however it had an
advantage that shot production ahead. In 1968, the American Society for Test-
ing and Materials issued a recommendation for the use of asbestos felt on built-
up roofs which helped asbestos felts quickly penetrate the roofing market. Now,
competition and health concerns appear to be dulling this edge. In 1976 built-
up roofing sales of all types were about 53 million squares. Organic systems
had about 45 percent of the market, asbestos felt 25 percent, and fiberglass
felt 10-15 percent. The remainder consisted of single ply and other roofing
systems. Some companies such as GAF and Nicolet Industries, have terminated
or cut back their production of asbestos roofing felt. From telephone surveys
it appears that the use of organic felt is widespread, at least in the North-
eastern United States. In the West and Soutwest tile roofs are common.
A product such as tile roofing, however, is suitable only for pitched roof
surfaces which are usually residential, as compared to built-up roofs where
asbestos is used. Tile roofs require little underlay, which likely increases
their popularity.
Since only organic felt roofs have been used in the United States for more
than 20 years, it is difficult to draw firm conclusions concerning the long-
term durability of the various roofing systems. Industry representatives differ
in opinions of superiority between asbestos, fiberglass, and organic felts, with
questions stemming from possible variability in fiberglass felt quality. Con-
version of asbestos felt manufacturing lines to the fiberglass felt mat product
79
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requires manufacturing experience and applicator training. Nevertheless,
fiberglass seems to be quickly gaining on the built-up roofing market. Problems
with alternative materials such as these are currently being investigated by
manufacturers; many difficulties will be minimized when installers become more
familiar with their use. If costs become more competitive, as they seem bound
to be with rising asbestos and petroleum product costs, there is every reason to
believe that dependable, cost-competive substitutes are available to replace
asbestos roofing felts.
TABLE 1. ROOFING COSTS
Roofing
felt type
Organic
felt
Asbestos
felt
Fiberglass
felt
Single-ply
membrane
system
Retail cost
per roll ($)
10.00
25.00
25.00
65.00
Installed cost
per square ($)
$50-60
$70
$70
$100
Cost includes labor and materials for base
sheet plus equal amounts of layers of felt.
Source: Telecon. D. Bailie, Koppers Company,
with N. Roy, GCA Corp./Technology Div.
July 11, 1980.
REFERENCES
1. Time/Life Books. Roofs and Siding. Alexandria, VA 1977.
2. Cogley, D. C., and N. K. Roy, et al. Asbestos Substitute Performance
Analysis. Draft Report. U.S. Environmental Protection Agency, Office
of Pesticides and Toxic Substances, Washington, D.C. March 1980.
3. Telecon. McLaughlin, E. Estimator, C and M Roofing, Somerville, MA,
with D. Ramsay, GCA Corp./Technology Div., August 20, 1979.
4. Telecon. Estimator, Matick Roofing Company, Chelsea, MA, with
D. Ramsay, GCA Corp./Technology Div., August 20, 1979.
5. Asbestos Industry Draft Profile, Prepared for OPTS, U.S. EPA, June
1980. EPA contract No. 68-01-5818.
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6. A. D. Little. Characterization of the U.S. Asbestos Papers Markets.
Prepared for the Minister of Industry and Commence - Government of Quebec;
Final Draft Report to Sores Inc. (Montreal), Report C-79231, 1976.
7. Anonymous. Manual for Built-Up Roofs. Published by Johns-Manville Corp.,
1978
8. Wright, M.D. et al. Asbestos Dust Feasibility Assessment and Economic
Impact Analysis of the Proposed Federal Occupational Standard, Part I:
Technological Feasibility Assessment and Economic Impact Analysis. U.S.
Department of Labor, Occupational Safety and Health Adminstration. Wash-
ington, D.C. Contract No. J-9-F-6-0225 Task 2. September 1978.
9. Contact with various industry sales persons by GCA Corp./Technology Div.,
1979.
10. Telecon. H. Chess, PPG Industries, Pittsburgh, PA, with S. Bianchetti,
GCA Corp./Technology Div., June 27, 1980.
11. Telecon. Ms. McKinney, Reichold Chemical Co., Irwindale, CA, with
S. Bianchetti, GCA Corp./Technology Div., June 27, 1980.
12. Telecon. D. Bailie, Koppers Company, Inc., Pittsburgh, PA, with
N. Roy, GCA Corp./Technology Div., July 9, 1980,
13. Telecon. A. Noble, Assistant Sales Manager, Koppers Company, Eastern
Division, West Orange, NJ, with D. Ramsay, GCA Corp./Technology Div.,
August 30, 1979.
14. Telecon. G. Perkins, R-625 Products Marketing Manager, Owens-Corning
Company, Toledo, OH, with D. Ramsay, GCA Corp./Technology Div.,
August 29, 1979.
15. Telecon. Salesman, Bradco Supply Corporation, Woburn, MA, with
D. Ramsay, GCA Corp./Technology Division, August 17, 1979.
16. Telecon. D. Bailie, Koppers Company, Pittsburg, PA, with N. Roy,
GCA Corp./Technology Div., July 9, 1980.
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DISCUSSION ON ROOFING PRODUCTS
QUESTION (Mr. Shaimes): Do you use the same number of plys for a glass fiber.
inlay as you use for organic fiber inlay?
ANSWER (Mr. Bailie): Right now, I think the industry is trying to reduce
the number of plys of felt used. You will find each producer with
his own various specifications. Most of the time, you will find the
same number of plys. I would not be surprised, in the future, as
the production of glass felts is firmed up, that the number will be
reduced; but as a rule, right now, I think it is most typical to
find the same number of plys. The use of a glass base sheet, a very
heavy glass, might become more prominent, thereby allowing the num-
ber of plys to be reduced even further.
QUESTION (Mr. Castleman): A couple of questions. One, do you have any
problems of irritation or skin reactions from workers handling the
fiber glass products; and, two, can you tell me the size distribu-
tion and diameter of the fibers used in the fiber glass product?
ANSWER (Chairman Guimond): I think the size question, relative to the fiber
glass product, will be discussed in the health-related session. I
personally do not know which size fibers are used.
ANSWER (Mr. Bailie): They will vary by different processing methods.
Certainly, when you handle fiber glass in its raw form, it can be
irritative. However, in fiber glass felts, the felt pretty well
encapsulates the glass fiber, so unless you happen to hit the edge
of the felt where it has been cut, you should have no irritation at
all. There is enough asphalt on it to protect you from the glass
fiber itself.
QUESTION (Dr. Millette): I am with the EPA Water Health Effects. I want
to make one comment about some work that we are doing on the
exposure of asbestos to home cisterns from different types of
roofing material.
We have not done a lot of work yet, but in one case we looked at
asbestos cement tiles and found that over a number of years, the
tiles had deteriorated by the weather. Therefore a roof that
collected water for a cistern would contain very high amounts of
asbestos. When we looked at several fairly old roofs that used
the asbestos roofing felt material, we did not find any fibers in
the drinking water of the cisterns that collected water from these
types of roofs. But we did take samples of the roof and dissolved
it and did find that fibers were present. But, apparently they
are well enough encapsulated that they did not come off in large
numbers into the drinking water. The third type of roof was
asbestos-containing coatings painted onto metal roofs. At least
in one case we have found some asbestos fibers in the drinking
water in that cistern.
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You gave a breakdown on the amount of different materials sold in the
last year or so. Do you have an estimate on how many residential
roofs in the United States would have asbestos felt materials in them?
ANSWER (Mr. Bailie): I seriously question whether any have asbestos felts
on them because it is quite unlikely that a roofing contractor would
use an asbestos asphalt saturated felt underneath shingles when he
can use an organic felt.
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MILL APPLIED COATINGS FOR UNDERGROUND PIPELINES
by
Mr. Jack Wink
Bredero Price, Inc.
Fairless Hills, Pennsylvania
ABSTRACT
The purpose of this discussion is to cover the fundamental philosophy for the
selection, application and performance of pipe coatings, as used for pre=
vention of the deterioration of metals buried in earth or submerged in water.
The basic function of a pipe coating on underground or underwater structures
±B to isolate the metal from contact with the surrounding environment. Metals
are unstable in these environments and reversion from their commercially pure,
unstable form to a more stable chemical compound is corrosion. Pipe coatings
form the first line of defense against this corrosion. Since a properly
selected and properly applied coating should provide approximately 99 percent
of the protection required, it is of utmost importance to know the advantages
and disadvantages of all available coatings. "The right coating materials
properly used will make all other aspects of corrosion control relatively
easy."1 This coating system will be supplemented with cathodic protection
to give the necessary overall corrosion control. Today with the many
coating systems available, the job of selecting the proper coating
necessitates careful analysis of the many desired properties for an effective
pipe coating.
PIPE COATING FUNDAMENTALS
The purpose of this discussion is to cover the fundamental philosophy for
the selection, application and performance of pipe coatings, as used for
prevention of the deterioration of metals buried in earth or submerged in
water.
The basic function of a pipe coating on underground or underwater
structures is to isolate the metal from contact with the surrounding environ-
ment. Metals are unstable in these environments and reversion from their
commercially pure, unstable form to a more stable chemical compound is
corrosion. Pipe coatings form the first line of defense against this
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corrosion. Since a properly selected and properly applied coating should
provide approximately 99 percent of the protection required, it is of utmost
importance to know the advantages and disadvantages of all available coatings.
"The right coating material properly used will make all other aspects of
corrosion control relatively easy.1" This coating system will be supplemented
with cathodic protection to give the necessary overall corrosion control.
Today with the many coating systems available, the job of selecting the
proper coating necessitates careful analysis of the many desired properties
for an effective pipe coating. The National Association of Corrosion
Engineers clearly defines the specific qualities that a pipe coating should
possess in NACE Standard RP-01-69, Section 5: Coatings.
Let us first review the desirable characteristics of a pipe coating:
1. Effective Electrical Insulator
Since soil corrosion is an electrochemical process in which an electrical
current flows from the structure to the soil carrying metallic ions with the
flow of current, a pipe coating has to stop this current by effectively
isolating the structure from the environment.
2. Ease of Application to Pipe
The coating material must be suitable for the intended service and
properly applied to be effective. There are many excellent pipe coatings that
require exacting application procedures that are difficult to maintain. Con-
sistent quality may best be obtained with a coating system that is least
affected by variables. Coating application specifications and good construction
practices combined with proper inspection contribute to the quality of the
finished coating system.
3. Applicable to Piping with a Minimum of Defects
This characteristic correlates with ease of application. No coating is
perfect, and that is why cathodic protection is required; however, no one
wants to buy a pipe coating that has too many holidays (voids in coating)
even before it leaves the mill.
4. Good Adhesion to Pipe Surface
Coating adhesion is important to eliminate water migration between the
metal substrate and the pipe coating. The coating adhesion assures perman-
ence and ability to withstand handling during installation without losing
effectiveness.
5. Ability to Resist Development of Holidays with Time
Once the coating is buried, two areas that may destroy or degrade
coatings are soil stress and environmental contaminants. Soil stress,
brought about in certain soils that are alternately wet and dry, creates
85
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tremendous forces that may split, bog or cause thin areas. Adhesion, cohesion
and tensile strength are important properties to evaluate in order to mini-
mize this problem. The coating's resistance to chemicals, hydrocarbons,
acidic or alkaline conditions has to be known in order to evaluate performance
in known contaminated soils.
6. Ability to Withstand Normal Handling, Storage and Installation
The ability of a coating to withstand damage is a function of its impact,
abrasion and ductile properties. Pipe coatings are subjected to a great deal
of handling between the time of application to the time of backfill. While
precautionary measures of proper handling, shipping and stockpiling are
recommended, the coatings vary in their ability to resist damage. Outside
storage requires resistance to ultraviolet rays and temperature changes.
These properties must be known and evaluated to assure proper performance.
7. Ability to Maintain Substantially Constant Electrical Resistivity
with Time
Since corrosion is an electrochemical reaction, a coating with a high
electrical resistance over the life of the system is important. The per-
centage of initial resistance drop is not as indicative of the pipe coating
quality as is the overall level of electrical resistivity.
8. Resistance to Disbonding when under Cathodic Protection
Since most pipelines will eventually be cathodically protected, it is
necessary for the coating to be able to withstand cathodic disbondment. The
amount of cathodic protection required is directly proportional to the quality
and integrity of the coating. Considering interference and stray current
problems, this becomes a most important requirement.
Cathodic protection does two things to a coating. First, it has the
ability to drive water through a coating which would ordinarily resist such
penetration. Second, it may produce hydrogen at the metal surface whenever
current reaches it and the hydrogen in turn will break the bond between the
coating and the metal surface. While no coating is completely resistant to
damage by cathodic protection, it is very important that we choose a coating
that will minimize these effects.
The ASTM G8-72 test for Cathodic Disbonding of Pipeline Coatings,
commonly known as the salt crock test, is a method used to measure a
coating's resistance to damage by cathodic protection. An intentional
holiday is placed in the coating being evaluated and the sample is immersed
in a 3 percent salt solution (1% sodium carbonate, 1% sodium sulfate, and 1%
sodium chloride.) Then when a negative electrical potential is applied through
the aqueous salt solution by means of an anode or rectifier, an electrical
current will flow through the solution to the bare metal surface as it would
in actual use. The sample is maintained at a constant potential and the
current drain that is required to protect the sample is measured periodically.
After a period of 30 to 90 days, the- sample is removed and examined for
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undercutting or any discontinuities. These discontinuities are easily
Identified by an accumulated calcite deposit around them. Relative resistance
of the coating to cathodic protection is determined by the number of un-
intentional holidays, by the amount or increase in current that has been
flowing and by the amount of cathodic disbondment or undercutting that has
occurred around the intentional holidays. The difference in the reaction to
this test by various coatings is sometimes very vivid. In some cases,
such a quantity of water is driven through the coating that the coating
develops large water blisters all around the sample. Then, in other cases, the
cathodic disbondment around the intentional holiday is so great as to cause
the entire sample to become disbonded from the surface. Then, of course, some
samples experience very frequent unintentional holidays. Some coatings, on
the other hand, exhibit no unintentional holidays, very little water being
driven through the coating and almost no cathodic disbondment around the
intentional holiday.3
9. Ease of Repair
Recognizing that some damage may occur, as well as the necessity of field
coating the weld area, compatible field materials are required to make
repairs and complete the coating after welding. Manufacturers' recommen-
dations should be followed. Field condition variables will influence your
selection of materials.
All nine of these properties are necessary and it is impossible to cite
one as being the most important, as they all contribute to a successful pipe
coating. However, perhaps we can agree that one property not specifically
listed under this recommended practice has the most influence on performance,
and that is resistance to water penetration. Once in its environment, water
penetration will effect performance in that absorbed moisture will carry
electrical current through the coating material and therefore, the electrical
resistance will be reduced. A rather simple test is often used to determine
water absorption and that is to measure weight gain following immersion for
a specific period of time. This test is not recommended, as the results are
not necessarily valid for evaluation comparison of different coating systems.
Factors to consider in this method are that some coating materials could be
dissolving ingredients at the same time they are absorbing water. Therefore,
a net weight increase would not be indicative of water absorption. The
thickness and the composition of the coating material would also be a factor
to consider in this method of evaluating coating systems based on water
absorption. A more accurate method is the ASTM G9-72 standard method of
test for water penetration into pipeline coatings. "This method consists of
an immersion-type test where pipe specimens are suspended in an aqueous
electrolyte for the duration of the test period. Electrical measurements
of coating capacitance and dissipation factor are used to follow the water
absorption rate of the test materials."1*
The following factors should also be considered when selecting a pipe
coating.5
87
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1. Type of soil or back fill
2. Accessibility of pipeline
3. Operating temperature of piping
4. Ambient temperatures during construction and installation
5. Geographical and physical location
6. Handling required and storage conditions
7. Costs
Evaluation of pipe coating properties coordinated with the above con-
siderations will assist in the selection process. Of the above factors,
the most misunderstood one is "costs". In pipe coating economics as in all
cost analysis, the end has to justify the means. In other words, the added
cost of coatings and cathodic protection has to earn its way by paying for
itself through reduced operating costs and longer life. "True" protection
costs should not only include initial costs of coating and cathodic protec-
tion but also installation, joint coatings and repairs.6 Field engineering
and facilities to correct possible damage to other underground facilities
that may be damaged by increases in current requirements may add additional
costs, possibly even outweighing the initial costs of the pipe coating.7
Another well known expression "that you get what you pay for" certainly has
application to the purchase of pipe coatings.
We have defined the purpose of a protective coating and have detailed
the desirable properties of an effective pipe coating. If any one coating
excelled in all these properties, it would be a perfect pipe coating.
Suffice it to say, we are still striving to design the perfect pipe coating.
How can you best select the pipe coating to meet your requirements?
Experience has proven a reliable method but how much experience, 20 years?
it has been approximately 23 years since the plastic coatings have become
available and only 5 to 7 years that present formulations have been on
the market. Many companies utilize accelerated tests as established by ASTM
to enable them to make a quantitative evaluation of these properties. You
as a user have to weigh the importance of these properties in light of your
own conditions.
We will now look at the different coatings available, describe their
properties and then how they are applied.
1. Enamels
The bituminous enamels are formulated from coal tar pitches or petroleum
asphalts and have been widely used as protective coatings for over sixty-
five years. Coal tar and asphalt enamels are available in summer or winter
grades. These enamels are the corrosion coating; they are combined in various
combinations of glass and/or felt to obtain mechanical strength for handling.
You should also specify that these materials meet requirements such as
National Association of Corrosion Engineers, National Association of Pipe
-------
Coating Applicators, or the American Water Works Association. The enamel
coatings have been the workhorse cdatings of the industry; and, when properly
selected and applied, can provide efficient, long-life corrosion protection.
Enamel systems may be designed for installation and use within an
operating temperature range of 30°F to 180°F (-1.1°C to 82°C). When tempera-
tures fall below 40°F (4.4°C), added precautions should be taken to prevent
cracking and disbonding during field Installation. Enamels are effected by
ultraviolet rays and should be protected by kraft paper of white wash. Enamels
are effected by hydrocarbons, and the use of a barrier coat is recommended
when known contamination exists. This coating is available on all sizes of
pipe. In recent years, the use of enamels has declined for the following
reasons:8»9
1. Reduced number of suppliers,
2. Restrictive O.S.H.A., E.P.A., and F.D.A. environmental and
health standards,
3. Increased acceptance of plastic coating materials, and
4. Alternate utilization of raw materials as a tuel.
For all pipe coatings, pipe should be ordered bare, free of mill coatings,
to permit the best surface preparation. Prior to blast cleaning the pipe is
heated to drive off surface moisture and loosen mill scale. The blast
cleaning will use sand or steel shot or grit or a combination of both to
obtain the desired profile and cleaned surface. Blasting operations shall
remove all rust, scale and other impurities from the surface, exposing base
metal over all, which presents a grayish matte appearance between Steel
Structures Painting Council Standard SP-6 and SP-10. This is equivalent to
NACE Standard TM-01, Visual Standards, between NACE No. 3 and NACE No. 2.
The blast cleaned surface is primed by brush, spray or by use of a
priming rag commonly known as a "granny rag." When the primer has dried
sufficiently, the coating and wrapping is performed by the hot application
of a bituminous coating which is pumped from the coating machine through
what is commonly called a spreader, from which the coating flows in a flood
coat onto the surface of the pipe. One important factor is to be sure that
the coating material is melted down properly and brought to application
temperature gradually. This is accomplished in an agitated kettle.
Agitation is needed to maintain uniform heat and to prevent the mineral
fillers (25 to 35 percent) from settling out. Settling of the fillers may
tend to develop what are known as hot spots, or carbon spots on the bottom
of the kettle. These small carbon spots will break down and get into the
coating material and eventually cause jeeps or holidays in the line. Carbon
spots are cathodic to the metal and will cause the metal to pit. Thus, the
melting operation and the mechanical agitators are of extreme importance.10
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An asbestos felt wrapper has generally been used as the outer wrap but
with restrictions on asbestos as a carcinogen, it is being replaced by a
glass wrapper. Care must be taken in application of the glass wrap, that it
is properly encapsulated with enamel to prevent a wicking action of moisture
from the environment to the steel.
Mill wrapping has many variations in specifications as to the various
types of bituminous coating materials which are applied to a nominal 3/32"
(.24 cm) thickness, followed by the glass or asbestos felt or combination
of both. Multiple coatings of enamel are often applied to build up the total
thickness where greater protection is required.
An electrical inspection of the completed coating should be made in
accordance with the procedures established by NACE Standard RP-02-74,
Recommended Practice for "High Voltage Electrical Inspection of Pipeline
Coatings."
For a more detailed treatment of this subject the ANSI/AWWA C203-78
American National Standard for Coal-Tar Protective Coatings is recommended.
2. Asphalt Mastic
Asphalt Mastic pipe coating is a dense, mixture of sand, crushed lime-
stone and fiber bound together with a select, air blown asphalt. These
materials are proportioned to secure a maximum density of approximately
132 pounds per cubic foot. This mastic material is available with various
types of asphalt. Selection is based on operating temperature and climate
conditions to obtain maximum flexibility and operating characteristics. This
coating is a thick, 1/2" to 5/8" (1.27 cm to 1.6 cm) extruded mastic re-
sulting in a seamless corrosion coating.
Extruded asphalt mastic pipe coating has been in use for over fifty
years. It is the thickest of the corrosion coatings and is cost effective
for offshore installations. Its ability to dissipate heat while providing
a relatively holiday free coating, has made it the most used pipe coating
for pipe type cable installations.1J>
Asphalt mastic systems may be designed for installation and use within
an operating temperature range of 40°F to 190°F (4.44°C to 88°C). Pre-
cautionary measures should be taken when handling in freezing temperatures.
Whitewash is used to protect it from ultraviolet rays, and this should be
maintained when in storage. This system is not intended for above ground
use or in hydrocarbon contaminated soils. This coating is available on
4-V to 48" O.D. (Optical Density) (11.4 cm to 122 cm) pipe.
The application procedure is as follows:12
Prior to blast cleaning the pipe is heated to drive off surface
moisture and loosen mill scale. The blast cleaning is accomplished by a
combination of shot and grit to remove all rust, scale and other impurities
from the surface, exposing base metal over all, which presents a grayish
-------
matte appearance between Steel Structures Painting Council Standard SP-6
and SP-10. (NACE No. 2, NACE No. 3). Pipe is then spray coated with an
asphalt primer prior to extrusion of the hot mastic mix to the circumference
of the pipe. This is a continuous extrusion which forms a seamless coating
bonded to the pipe. Whitewash is applied to reflect the sun's rays and to
facilitate stockpiling. An electrical inspection of the completed coating
should be made in accordance with the procedures established by NACE Standard
RP-02-74. Recommended Practice for "High Voltage Electrical Inspection of
Pipeline Coatings." Holidays are patched and retested. Patching is
relatively easy, because the mastic is thermoplastic, it is heated and worked
with a trowel to reseal.
3. Extruded Plastics - Polyethylene and Polypropylene
The extruded plastic coatings have been available to the industry since
1956 and their growth and acceptance has been remarkable during this period.
Initial problems of stress cracking and shrinkage have been minimized by
better quality and grade of high molecular weight polyethylene resins. There
are presently two systems available in the United States. One is an
extruded polyethylene sleeve which is shrunk over a 10 mil asphalt mastic,
and the other is a dual extrusion, where a butyl adhesive is extruded onto
the blast cleaned pipe followed by multiple fused layers of polyethylene.
The latter method utilizes multiple extruders in a proprietary method which
obtains maximum bond with minimum stress. The sleeve type is available on
1/2" through 24" O.D. (1.3 cm to 61 cm) pipe, while the dual extrusion is
presently available on 2*5" through 103" (6.35 to 262 cm) pipe. The operating
temperatures range for polyethylene systems from -40°F to 180°F (-40°C to 82°C)
and for polypropylene it is -5°F to 190°F (-21°C to 88°C). The polyethylene
systems have been successfully field bent (1.9° per pipe diameter length)
at -40°F (-40°C). Swelling may occur in hydrocarbon environments. Polyeth-
ylene has excellent dielectric strength. With the proper selection of polyeth-
ylene resins and the addition of 2% percent carbon black, the dual extrusion
system has withstood long term aboveground storage and aboveground use. An
electrical inspection of the completed coating should be made in accordance
with NACE Standard RP-02-74 Recommended Practice for "High Voltage Electri-
cal Inspection of Pipeline Coatings."
The application methods are as follows:
Both methods preheat bare pipe prior to grit blast cleaning to a
commercial blast clean. With the sleeve type coating, the adhesive
undercoating is applied by flood-coating the hot material over the pipe
before it passes through an adjustable wiper ring which controls the thick-
ness. After the mastic is applied, the pipe passes through the center of
the crosshead die where the plastic is water quenched to shrink it around
the undercoating and pipe. Following electrical inspection, pipe ends are
trimmed for cut back and the coated pipe is stockpiled.
In the dual extrusion system, the cleaned pipe is rotated at a cali-
brated rate through the process. The first of two extruders applies a film
of butyl adhesive of predetermined width and thickness, fusing the film to
91
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the rotating pipe in two layers. While the butyl is still in a molten state,
high molecular weight polyethylene is applied from the second extruder in
multiple layers of a predetermined thickness, producing a bonded coating
50 to 100 mils thick. Water quenching, electrical inspection and cut back
is completed prior to stockpiling.
Polyethylene systems have been in use in Europe for approximately fifteen
years with both crosshead and side extrusion methods. In addition to the
butyl adhesive or asphalt mastic adhesive, some systems use a polyethylene
copolymer adhesive. This system requires high temperature 200°C (390°F)
heating for application of the adhesive.13
For a more detailed treatment of extruded plastic pipe coating systems
the reader is referred to the paper "Extruded Plastic Pipeline Coatings.11*
4. Fusion Bonded Thermosetting Powder Resins
Fusion bonded powder pipe coatings were first introduced in 1959 and
have been commercially available since 1961. These coatings are applied to
preheated pipe surfaces 400°F to 500°F (204°C to 260°C) with and without
primers. On some resins, post curing is required for complete cure. This
coating is applied in a 12 to 25 mil thickness. The fusion bonded powder
coatings exhibit good mechanical and physical properties and may be used
above or below ground. Experience has indicated that on above ground
installations, to eliminate chalking and for longer service life, it is
recommended to topcoat with a urethane type paint system. Of all the pipe
coating systems, the fusion bonded thermosetting resin systems, when properly
applied are the most resistant to hydrocarbons, acids and alkalies.
Perhaps the main advantage of the fusion bonded powder pipe coatings
is that they cannot cover up apparent steel defects because of their lack of
thickness, so they do permit excellent inspection of the steel surface before
and after coating. The amount of holidays that may occur is a function of
the surface condition and the thickness of the coating specified. A recent
steel surface profile study by Dr. Bruno and Ray Weaver of the Steel Structures
Painting Council (SSPC) found the following effect of blast cleaning on
steel: "Dr. Bruno and Ray Weaver of the SSPC explained that viewing shot
or grit blasted surfaces in three dimensions reveals surface characteristics
not visible in two dimensions. SSPC research has uncovered the existence
of abrasive-formed spikes of steel that protrude from one to ten mils from
the surface.
SSPC researchers have dubbed these phenomenons "hackles" and believe
that they are formed by the cutting action of the abrasive. Weaver said that
a hackle may be created when a piece of abrasive strikes a work stress area.
In three dimensions, the hackle stands out in stark relief against its
surroundings, but is barely visible in two dimensions.
Dr. Bruno said that hackles are difficult to locate and unpredictable.
One never knows how many one will find in any given area of surface studied,
he said, and their effect on coatings is not known."15
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Increasing the thickness of the applied coating minimizes this problem
and with minimum cathodic disbondment characteristics, it has proven to be
a most serviceable pipe coating. These coatings are available on 3/4" - 48"
(1.9 cm - 122 cm) O.D. pipe.
The application procedures for thermal bonded powder resins are less
tolerable of variables and more care is required to properly apply them.
Prior to cleaning, pipe is heated to remove moisture and loosen mill scale.
It is necessary to clean the surface to a near-white metal finish as defined
in SSPC-SP10 (NACE No. 2).
Pipe is then heated uniformly to the recommended application tempera-
ture (400°F - 500°F/204°C - 260°C). Each material has its own requirements
and tolerance level which must be strictly adhered to. If a primer is
required there are minimum maximum overcoat times which are necessary to
follow. The powdered resin is applied by electrostatic deposition to the
12-25 mil thickness specified. Certain resins require post heat treatment
for proper cure. Inspection by a minimum of 100 volts per mil of thickness
is recommended. Pipe requiring limited repair (to be agreed to between
customer and applicator, perhaps one holiday per ten square feet) due to
hackles, coating imperfections and other minor defects shall be repaired by
use of a heat bondable polymeric hot metal patch stick. A 100 percent solids
liquid epoxy repair material is recommended within 12" of each end of pipe.
Manufacturers recommendations for field application of patching materials
should be followed.
For a more detailed treatment on Fusion Bonded Thermosetting Powder
Resins, the reader is referred to the ANSI/AWWA C215-78 standard.
5. Liquid Epoxy and Phenolics
There are many different liquid systems available today that cure by heat
and/or chemical reactions; some are solvent types and others 100 percent solids.
Their use is mostly on larger diameter pipes where conventional systems may
not be available or where they may offer better resistance to operating
temperatures in the 200°F (90°C) range.
Generally epoxies have an amine or a polyamide curing agent and require
a near-white blast cleaned surface SSPC-SP10, (NACE No. 2). Coal tar epoxies
have coal tar pitch added to the epoxy resin. A coal tar epoxy cured with a
low molecular weight amine is especially resistant to an alkaline environment
such as occurs on a cathodically protected structure. Some coal tar epoxies
become brittle when exposed to sunlight.16
The application for a mill-applied system is as follows: The pipe is
placed on rotating rollers mounted on a tracked dolly which automatically
feeds the pipe into a grit blasting machine. It is cleaned inside and out.
Then it is transferred into a spray booth where the interior and exterior
may be simultaneously coated with two separate spray coats to provide a dry
film thickness of 12 mils. After which the coated pipe is then subjected to
hot air blowers for proper curing prior to inspection at 100 volts per mil.17
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6. Tapes
Polyvinyl, polyethylene and coal tar tapes are widely used In the field
for joint coating protection or for odd shapes or bends on mill applied
applications. The trend has been to heavier butyl-mastic type adhesives to
provide better adhesion and eliminate water migration at the overlap. When
tapes are applied at a coating plant, padding or rockshield must be provided
to minimize shipping damage. Over the trench, field applied tapes may be
applied with tape wrapping machines. Coatings applied over the ditch are
less susceptible to physical damage because of reduced handling, but they can
be more affected by variations in ambient temperatures and humidity. These
along with inadequate surface preparation are the main disadvantages of a
field applied coating system. The important developments in plastic tapes
have been an increase in their thickness, use of stronger resins and improved
adhesion by the use of new types of adhesives and primers. Mill applied
tapes capable of service temperatures to 210°F (99°C) are presently available
and have had limited use.
7. Wax Coatings
Presently not too much is heard regarding the use of wax coatings.
However, they have been in use over 48 years and are still utilized on a
limited basis. Microcrystalline wax coatings are usually used with a plastic
overwrap. The wax waterproofs the pipe and the wrapper protects the wax
coating from contact with the soil and affords some mechanical protection.
The most popular use of a wax coating is the over-the-ditch application with
a combination machine which cleans, coats, wraps and lowers into the ditch
in one operation. The fact that there are no objectionable or toxic fumes
or smoke present should make this system more acceptable.
8. Polyurethane Foam Insulation
Efficient pipeline insulation has grown increasingly important as a
means of operating hot and cold service pipelines. This is a system
controlling heat transfer in above or below ground and marine pipelines.
While generally used in conjunction with a corrosion coating, if the proper
moisture vapor barrier is used over the urethane foam, effective corrosion
protection is obtained. This is a plant applied process, where the carrier
pipe is centered within the outer jacket which contains and molds the foam
as well as providing an effective moisture vapor barrier. Metered quantities
of foam components are rapidly introduced between the carrier pipe and the
outer jacket. The foam is restrained by end caps and rises on a first-in
basis forming a uniform composite unit. When properly jacketed, usually with
polyethylene or coated steel, the system is moisture and corrosion resistant
and sufficiently strong to resist crushing and flexible enough to permit
allowable field bending.18
9. Concrete
Mortar lined and coated pipe have the longest history of use to protect
steel or wrought iron from corrosion.19 When steel is encased in concrete,
a protective iron oxide film forms. As long as the alkalinity is maintained
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and the concrete is Impermeable to chlorides and oxygen, corrosion protection
is obtained. See AWWA C-205 for a detailed reference on concrete coatings.
Today concrete as a corrosion coating is mainly limited to internal
lining. The external application is applied over a corrosion coating for
armor protection and negative bouyancy in marine environments. A continuous
reinforced concrete coating has proved to be the most effective controlled
method of obtaining desired results.
Materials including water, sand and/or heavy aggregate, and cement are
mixed in the application plant. The materials are conveyed by belt to the
throwing heads where controlled-speed belt/brushes throw the mixture onto
the coated pipe surface. The rotating pipe is moved past the throwing heads
to receive the specified thickness of concrete. Simultaneously the galvanized
wire reinforcement is applied with an overlap. To further increase tensile
strength and to improve impact resistance additional layers of wire or steel
fibers may be specified.20
We have now covered the most popular protective coatings and described
their properties and how they are applied, but I would be remiss if I stopped
here. In the foreword to the N.A.C.E. recommended practice "Application
of Organic Coatings to the External Surface of Steel Pipe for Underground
Service," I quote, "Experience Shows that a Major Cause of Pipeline Coating
Failure is due to Improper Application."21 Therefore the selection of an
applicator might prove to be the most important consideration. A quality
material poorly applied is of little value and the quality of your pipe
coating is only as good as the quality of application. To assist you in your
evaluation of an applicator, the following points should be considered:*2
1. Experience
2. Reputation
3. Reliability
4. Conformance to coating manufacturers specification
5. Modern automated equipment
6. Quality control
1. Experience
A lot of research and also trial and error has gone into the develop-
ment of every coating that is now on the market. This has required close
cooperation between applicator, coating manufacturer, equipment manufacturer
and customer. The transition from laboratory to production line is usually
a costly experience but the value of having accomplished this cannot be
underestimated.
2. Reputation
This is an asset that has to be earned through performance as promised.
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3. Reliability
Consistent quality performance that can be depended upon.
4. Conformance to Coating Manufacturers Specifications
Manufacturers have established minimum specifications for application of
their materials which should be met, if not exceeded.
5. Modern Automated Equipment
Capital expenditure on automated application equipment has been an
important part of the overall success of plastic coatings. The elimination
of human errors through automation and controls will continue to be an
important factor in obtaining improved pipe coatings.
6. Quality Control
Conformance to specifications has to be checked regularly. Knowledge of
applicators quality control procedures on materials, application and finished
product are essential in the selection of an applicator.
To summarize, it is not an easy task to select the "best" coating system
for your needs. This selection requires knowledge of your operating and
installation conditions to be able to evaluate the properties of the pipe
coatings as to filling these needs. 1 reemphasize that selection of a quality
applicator is the most important consideration and frequently is the most
neglected. After the coating and applicator have been selected, inspection
at the coating mill and especially during construction phases will go far in
assuring that you are obtaining maximum benefits from your pipe coating
system.
REFERENCES
1. A.W. Peabody, Control of Pipeline Corrosion, Chapter 3 "Coatings",
p. 9-18.
2. NACE Standard RP-01-69 Recommended Practice "Control of External
Corrosion on Underground or Submerged Metallic Piping Systems".
Section 5.1.2.1, p. 5.
3. S. Boysen, Jr., "Coating Fundamentals", Appalachian Underground
Corrosion Short Course, May 1974.
4. This ASTM method is under the jurisdiction of ASTM Committee G-3
on deterioration of non-metallic materials. American Society for
Testing and Materials, 1916 Race St., Phila., Pa. 19103.
5. NACE Standard RP-01-69 Recommended Practice "Control of External
Corrosion on Underground or Submerged Metallic Piping Systems".
Section 5.1.2.2, p. 5.
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6. Jack T. Kluchi, "Plastics for the Protection of Underground Pipe",
March 1, 1967, Purdue University, 6th Annual Underground Corrosion
Course.
7. O.W. Wade and J.F. Gosse, "A Study of Test Methods for External
Coatings for Underground Pipelines," 1966 American Gas Association
Distribution Conference.
8. Dean M. Berger, "Selecting Coatings for Underground Steel Pipe",
Plant Engineering. September 30, 1976, p. 105.
9. R.W. Horner, "Extruded Plastics", May 1973, 18th Annual Appalachian
Underground Corrosion Short Course.
10. K. Channing Verbech, "Protective Coatings," New England Gas
Association, June 19, 1969.
11. R.N. Sloan, "Present Trends in Coatings to Protect Pipe Type Cable in
the Utilities Industry" Materials Performance, July, 1979, p. 27-30.
12. R.N. Sloan, "Asphalt Mastic Coatings," Fifteenth Annual Appalachian
Underground Corrosion Short Course 1970.
13. N. Schmitz-Pranghe, "Mannesmann's Approach to Extruded PE Mill Coating"
Pipeline Industry, March 1976, p. 40.
14. R.N. Sloan, "Extruded Plastic Pipeline Coatings" NACE Southeast
Regional Conference, Oct. 21-24, 1979.
15. Dr. Bruno, Ray Weaver, SSPC Research Program American Painting Contract-
or, Dec. 1976, p. 14.
16. Dr. Richard W. Drisko, "Introduction to Protective Coatings," p. 7/3.
Materials Science Div., Naval Construction Battalion, Port Hueneme,
Calif. 93043.
17. Linden Stuart, Jr., "Modern Pipe Coating Techniques and Equipment in
the Mill and Field". Corrosion 78, NACE Paper No. 65.
18. Price, Prilo-K Polyurethane Foam Insulation Bulletin 1977.
19. John G. Hendrickson, "Internal and External Concrete Coatings for
Corrosion Control", 15th Appalachian Underground Corrosion Short
Course, 1970, p. 358.
20. Pipeline & Gas Journal Staff Report "Steel Fibers Toughen Coating for
Offshore Pipelines", May 1975.
21. NACE T-10D-8 Proposed NACE Standard Recommended Practice for "Appli-
cation of Organic Coatings to the External Surface of Steel Pipe for
Underground Service".
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22. R.N. Sloan, "Protective Coatings", New England Gas Association
Corrosion Course, Worcester Polytechnic Institute, Worcester, Mass.,
June 21-23, 1967.
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DISCUSSION ON PIPELINE WRAP
QUESTION (Mr. Ward): You talked a lot about oil pipelines and heat waste
pipeline applications underground. Would you address the above-
ground or in-plant steam pipes?
ANSWER (Mr. Wink): I did overlook that big market. Cross-country pipe-
line is basically what I talked about because that is what I am
most familiar with. When you get to your petrochemical plants,
utility plants, or another type of industry, you have overhead
pipelines. There is a different corrosion problem as opposed to
being in the soil. Different types of coatings must be looked at.
Most predominant Is the phenolic epoxy, a liquid type coating that
is sprayed on.
One important thing to consider is the temperature of the line.
You mentioned steam, which can be 800 or 900 degrees; a very special
painting is needed for this in order to withstand the heat and pre-
vent the pipe from disbonding. Napguard could possibly handle
temperatures of that nature.
Coatings undergo worse corrosion aboveground than with a buried
pipeline and maintenance is probably a year-around aspect of this
type of situation.
QUESTION (Mr. Ward): I am also thinking of thermal insulation.
ANSWER (Mr. Wink): For thermal insulation, polyurethane foam is good up to
about 300 degrees Fahrenheit. With steam lines, which have high
temperatures, you probably want to look at calcium silcate.
QUESTION (Mr. Castleman): I would like to know how long polyurethane foam
has be*»n around, and was asbestos insulation used before the poly-
urethane foam?
ANSWER (Mr. Wink): I am really not familiar with asbestos being used as
an insulation.
QUESTION (Mr. Castleman): I mean underground.
ANSWER (Mr. Wink): Polyurethane foam, to the best of my knowledge, has been
used since the early 1950s. I know a couple of jobs overseas where
urethane foam was used, but it primarily replaced calcium silcate,
which is a very brittle pipe insulating material.
QUESTION (Ms. Levy): I am from the Health Standards Bureau of OSHA. This is
a general question to all the members of the panel. I have heard a
lot now, and I am encouraged by hearing that you have new substitutes
for asbestos. I would like to know to what extent you are thinking
about new processes, that is, rather than just plugging in a substi-
tute for asbestos, are you looking at materials that would change
exposure levels. Is any research being done in that area?
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ANSWER (Mr. Wink): I will try to attack the question from my standpoint and
then I will pass it on. Primarily, whereas applicators are con-
cerned, the affect of asbestos in our industry is small — it is more
in the manufacturing aspect. In one material we replaced asbestos
with fiber glass, and primarily, that is what the pipeline industry
will do—just replace asbestos with other material.
QUESTION (Mr. Bailie): Is your question to change the process of production
to handle asbestos or is it to change the process completely to
eliminate asbestos?
QUESTION (Ms. Levy): Well, I am unclear as to how much asbestos you are
going to eliminate, but from what I have gathered, some of the sub-
stitutes will still involve exposures. There is still going to be
some exposure unless you change the workers' direct contact to
some extent, and I am curious about how that is going to come about,
if at all, and is there any ongoing research?
ANSWER (Mr. Bailie): Relative to the roofing industry, the exposure to
asbestos is rather minimal. It is more prevalent at the production
point. To that end, I cannot speak with any authority. I am sure
that your department has leaned heavily on the producers of asbestos
felt to the point that they are taking every precaution in changing
their process.
REMARK (Chairman Gulmond): If I interpret you correctly, you are saying
that where you may have a process now that is using asbestos or
some other kind of fiber, such as fiber glass or mica, either as a
filler or as a binder, are companies changing the processes of
making those pipes or insulations so that the whole system might be
enclosed, so as to eliminate exposure.
REMARK (Ms. Levy): Right.
ANSWER (Mr. Bailie): I can only say this, in the area in which our corpora-
tion uses asbestos, we have spent a lot of money to, first of all,
comply with your requirements, and second, to provide as much pro-
tection as is possible for the workers involved. I think that can
also hold true for the producer of roofing felt.
QUESTION (Chairman Guimond): You have indicated that there seems to be a
transition occurring from asbestos to alternative materials. Do you
know approximately what fraction of the market these alternatives
have at the present time?
ANSWER (Mr. Wink): I would guess, offhand, the coal tar industry, which
is the biggest user of asbestos, is now using fiber glass. This
is about 50 to 55 percent of the pipeline industry. The other
coatings comprise the remaining 45 to 50 percent.
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TEXTILES
by
Mr. Samuel 6. Manfer
The Carborundum Company
Niagara Falls, New York
ABSTRACT
Many U.S. companies, some of them former asbestos weavers, have expended
effort into the development of products to replace asbestos textiles.
Aramids, ceramic fiber, fiberglass and silica have all been processed into
textiles which have gained acceptance as substitutes in many applications.
Major uses for asbestos textiles have been as gaskets, packings, heat shields
and personal protection. Current replacement products have certain, but not
all, performance characteristics necessary to be suitable substitutes in all
applications. Silica and ceramic fiber products, for example, resist
extremely high temperature and most chemicals but will not withstand abrasive
conditions. Inversely, aramids, while possessing good strength and
mechanical resistance, can only be used in temperatures under 650°F.
In most cases, non-asbestos substitutes are more expensive than the asbestos
products they replace. For certain uses, the additional cost is economically
justified by a longer service life. In applications where performance is
relatively equal, health and environmental considerations are usually the
justification.
While many substitutes are available, no one particular product can be
used to replace asbestos in every application. Careful consideration of the
application is necessary to determine the appropriate substitute.
My product today is TEXTILES — Asbestos Replacement Textiles in
particular. I guess it may be somewhat bold, but it is safe to say that
there is now a replacement for every asbestos textile product. When I first
became associated with asbestos replacement, price and performance seemed to
be the problem areas. These are no longer problem areas. There are products
that are very price-competitive and there are products that perform better
than asbestos. My discussions today will not cover friction-oriented textile
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products such as clutch facings and brake lining materials. Additionally, I
will not talk about dynamic packings. These topics have been covered earlier.
The areas I am going to cover are the woven cloth and tapes, ropes and braids,
tapes and sleevings.
The market is big — very big — much bigger than most people would think
for this particular product line. We conservatively estimate yearly purchases
of $50 to $70 million dollars or 5 to 6 million pounds a year for just textiles.
The business is big with innumerable applications. The applications are
welding cloth, maintenance cloth, furnace curtains, expansion joints, static
packings and general packings, furnace door seals, flange gaskets, burner
gaskets, boiler door seals, pipe wrapping and cable protection, safety garments,
gloves and insulation sales. So far, replacement textile products have pene-
trated only 10 percent. The big problems are marketing and user expectations.
It starts with the user who purchases from a fabricator or distributor who is
supplied by the manufacturer. The user is the key person. He's really
unsure of his service conditions. Asbestos always worked and was specified.
Asbestos textiles have been maintained items. It was always on hand and used
universally. It always worked and it was always specified for key engineered
applications.
Direct substitution is difficult. You just cannot throw in a replacement
product where an asbestos product used to be and expect the exact same
performance. Application-by-applicatiori replacement is necessary. Usually
traditional mill supply houses, or asbestos specialty distributors stocked
and delivered. The user must now deal with other people. The forms may be
different. Instead of a 40 inch cloth, he may now have to use a 36 inch
cloth. Or he may want to use a paper or a felt to do a job.
There is really little incentive. What sort of pressure are we putting
on people? The dangers aren't really apparent. You see asbestos and do not
take it seriously. "I'm not going to get that fiber into my lungs. What
are the chances of that one fiber getting in there?" A lot of people think
that way. However, there is a lot of pressure from the foremen and the super-
intendents to keep the production up. Trying new products causes problems
that affect production. This is a big hurdle to overcome. They want some-
thing that is better and cheaper, rather than safer and acceptable.
In regard to the fabricator, they are not too anxious to change either.
They have to come up with new methods. Asbestos used to crease when they
were making their blankets. Substitutes do not crease too well. New methods
have to be used — new molds, dies, new forms. Wetting agents are required
for coating whereas plain water or mortar was used before. Problems exist
with irritability, abrasion and dust.
From the distributor standpoint, these are the people who have to sell
the product to the end user. They need to stock more products now. Before
they used to stock one or two different types of asbestos cloth and that took
care of all the needs. Now they have to stock maybe 4 or 5 different products
and that is not too attractive. That is more inventory, more dollars. They are
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unsure how willing the customers are going to accept and how willing they are
to convert or what they are going to convert to. They need more initial
service and selling effort to convert the customer. That means more salesmen
and more field service. This means more people or more overhead. Profitability
requirement for price, discount, and service are different. They're different
for the different types of distributors.
The manufacturers, the people who make these textile products, they
really do not know the end uses. For so long asbestos manufacturers have been
a material supplier. The fabricators and distributors really know the nitty
gritty application details. Manufacturers supplied asbestos and asbestos
worked. What are the real needs of the end user? What are his service
requirements? Does the end user really know whether his pipeline is 500
degrees or 300 degrees? Is the door seal going to see 1000 degrees or
really only 600 degrees, or maybe 1500 degrees? They do not have the knowledge
of the real user problems. The manufacturers have to develop replacements but
do not know the key applications and the key service requirements. They are
held to a specification written around asbestos. When you try to make a
product that is around an asbestos specification and the product is not
asbestos, it is very difficult to duplicate. But it is possible to meet the
service requirements with different materials and forms.
The manufacturers are not familiar with the fabricators, or the distri-
butors of the end users' needs. Some need price, discount, service and some
need different types of performance requirements. Application selling is
required by the manufacturers. They have to invest in people to get to the
individual accounts, and the individual end users to find all those applica-
tions one by one and determine what product can replace the asbestos. These
are what I consider the major problems in replacing asbestos textiles.
Let me talk a little bit about the products available and some of the
requirements necessary for them. Replacement products have three common
requirements. They must be temperature resistant, inflammable and flexible.
Cloth products need molten metal resistance, wear and abrasion resistance,
the ability to be fabricated and mechanical strength. Some examples are
welding curtains, maintenance blankets, slow cool blankets, expansion joints
and furnace curtains. Packings need resiliency, chemical stability, durability,
abrasion resistance and the ability to be coated. Some static packings
used to prevent leaking of gasses, must have good scalability, compressi-
bility and recovery characteristics. Burner gaskets and pipe wrappings need
good mechanical strength, vibration strength and molten splash resistance.
Clothing must be non-irritating, coatable and easy to fabricate.
There are several types of fibers that are being used for asbestos
substitution.
Fiberglass is currently very popular with a wide range of acceptance.
It can be used very successfully in certain applications. Advantages are:
it has moderate thermal resistance, 1000 degrees, it can be blended with
other fibers, it is relatively low cost and it has good mechanical strength.
The disadvantages are; it has poor abrasion resistance at higher tempera-
tures, it has limited molten metal resistance, it is irritating to workers'
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skin, and it has poor scalability. These are not concrete advantages and dis-
advantages. In each application the advantages and disadvantages may be dif-
ferent. Some of the leading contenders—for example PPG and Owens Corning—
seem to be the strong supporters of asbestos replacement textile fiberglass.
PPG has introduced Text'o and Owens Corning also has texturized fiberglass pro-
ducts. The texturized product is a product that was developed, in my
estimation, to look similar to asbestos and to provide thermal insulation
characteristics. Many users are finding that non-texturized fiberglass or
continuous yarn fiberglass products are well accepted in the marketplace. It
is a trend toward people being open minded. A product does not necessarily
have to look like asbestos in order to substitute for asbestos. Some of the
products made from this are Zetex fiberglass cloth and Uentley Harris rope
products.
The advantages of ceramic fiber are good heat resistance (it withstands
2300 degress without any degradation and can withstand temperatures up to
3000 degrees), it is inflammable, it has good thermal shock resistance, it has
molten metal resistance, it can be blended with other material. It has
good mechanical strength, good chemical resistance, and can be coated and
fabricated. Major disadvantages are its abrasion resistance, it needs organic
carriers to be formed and it is abrasive. There is one form that 3M produces
that does not have an organic carrier. It is a continuous form as opposed to
a staple. Another form of this is leached silica fiber. The advantages here
are good heat resistance, heat resistance to 1800 degrees, inflammability
and good molten metal resistance. Disadvantages are that they are brittle at
the higher temperature, have poor abrasion resistance and are moderately high
cost. New aramids have heat resistance to 600 degrees, have high strenth
in the Kevlar form, are non-abrasive, can be blended with other fibers and
have good scalability. Aramids are good in the packing areas. Disadvantages
are low strength (Nomex), they are difficult to weave and cut (Kevlar) and
they are moderately high cost. Some of the leached silicas are Refrasil and
Siltemp. The aramids are Nomex and Kevlar, both made by Dupont. Amatex
also fabricates aramids into a line of textile products. Other new fibers
are carbon fibers which have good thermal properties, scalability and lubricity.
Disadvantages are lack of flexibility, poor abrasion resistance, limited
vibration resistance, and very high cost. Another fiber is stabilized
PAN or better known are the Preox materials. Advantages are flexibility,
vibration resistance, good tear strength and good fabrication characteristics.
Disadvantages are heat resistance, molten metal resistance, cyanide for-
mation upon heating, and high cost.
Carborundum feels very strongly and is committed very seriously to ending
the no asbestos blues. We feel strongly that asbestos can be substituted
for. We are heavily committed to this right now and have a line of textile,
paper, board and cement products. Our feeling is that if people are open
minded about changing the form it does not necessarily have to be a textile
to serve the need.
For example, we have successfully wrapped pipes with paper as opposed to
wrapping it with a textile tape. It is a low cost way to insulate a pipe.
The disadvantages are that it does not have a good durability or abrasion
resistance. However, if it is covered, it is a low cost way to go about
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replacing asbestos textiles. Another example is a CalRod heater used by the
Navy. Where they formerly used textiles, they now use ceramic paper. Gas-
kets have been cut out of textile products. They are now being replaced by
board and lightweight papers that serve the same need. Board products are
replacing textile cloths in the steel industry as splash protection.
Asbestos is a widely used fiber. It has been around a long time and
has had over a century for development of uses and applications. The replace-
ments may work but they are not identical to asbestos. People must have the
desire to convert.
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DISCUSSION ON TEXTILES
QUESTION (Mr. Cronin): I am with the Safety and Health Department of the
Steel Workers Union.
My first question is about fiber diameters. I have seen products
like your own, for example, manufactured in many different fiber
diameters, ranging all the way from 10 to 15 microns on the upper
end, down to, for some products, the submicron size. I am
wondering first, why would one use a larger diameter in some
applications and a smaller diameter fiber in others?
Second, what is the cost differential for those two different
kinds of fibers?
ANSWER (Mr. Manfer): The way Carborundum makes fibers and the way most
ceramic and fiber glass manufacturers make their product is the
longer the fiber, the greater the diameter in a staple form.
Usually, the longer the fiber, the more mechanical strength in a
product. That is the reason for the long fiber. The short fiber
is used for more volume orientation, so you can use it in rein-
forcing applications, which do not need mechanical strength, but
need a heat dissipater.
Cost-wise, I would probably say the short staple, from our vantage
point and that of most ceramic manufacturers, is cheaper because
it can be produced much faster and in large quantities. A slower
process is required to make the longer fiber and it is therefore
more expensive.
Are you looking for relative cost differential?
QUESTION (Mr. Cronin): Why would one use very thin fibers at all? What
is the reason or advantage for using the fibers about which there
have been, at least, some preliminary health questions?
ANSWER (Mr. Manfer): Usually a fine fiber is necessary for insulation.
The finer the fiber, the more air void you can create; the more
air void, the better the insulator.
QUESTION (Mr. Cronin): Let me ask you one final question. In the very
beginning of your talk you said you know of a nonasbestos textile
replacement for every asbestos use. Is there a nonrespirable
or a thick fiber replacement, and let us define that as being
more than 5 micrometers, for every current asbestos textile
use.
ANSWER
(Mr. Manfer): I am not sure.
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QUESTION (Mr. Cronin): Can you, for example, make the Insulation layer
thicker? For example, can y6u achieve the same effect as high
temperature Insulation with thicker fibers and a greater massive
Insulation as in a thicker insulation layer around a furnace?
ANSWER (Mr. Manfer): Yes, you can. The problem is the thicker the fiber,
the less air space you have, and the thicker the material. I know
of many fiber glass uses above the 5 micron level. I think they
are running about 10 microns. Fiber glass can not replace every-
thing. Ceramic fibers can range from 3 to 10 microns, and they
replace a lot of asbestos. I am not exactly sure what the other
fibers diameters or lengths are.
QUESTION (Mr. Weiner): I am from the Navy Department.
Did I hear you correctly to say that cyanides come off of carbon
fibers, or was that another fiber you talked about?
ANSWER (Mr. Manfer): No, it was stabilized PAN, which is polyacrylic
nitrate, also called Preox. It is not off the carbon fibers.
QUESTION (Mr. Castleman): I divide my time between working as a consultant
for the Office of Toxic Substances of the Environmental Protection
Agency, working for the Environmental Defense Fund, and working
for attorneys representing plantiffs in damage suits against the
asbestos industry.
I would like to know if Carborundum is feeling pressure from the
Importers of Amatex, who, as you must know, plays on both sides
of the fence and has two asbestos textile plants in Mexican border
towns; is this hurting your ability to market your product?
ANSWER (Mr. Manfer): I would say asbestos Imports do not help our
situation. I cannot specifically say that it has hurt us, I
cannot claim any damage, but it does not help.
QUESTION (Mr. Wyblan): I am from the University of Minnesota.
Going back to fiber diameters, do you have a general idea of the
range of diameter, say, for something that you are calling 10
microns? What is the range of the size distribution for fibers
like that?
ANSWER (Mr. Manfer): I really have to defer that to my technical people.
QUESTION (Mr. Ross): I am from the U.S. Geological Survey.
Let us pursue diameters a little more since you want to replace
all asbestos with a product, I assume, that will not cause
disease. Yet you do not know much about the fiber diameters. You
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see, if we start replacing asbestos with substitutes with fiber
diameters in the respirable range, then a health problem might
arise 20 years from now. I think we should be a little harder
nosed about what we are going to replace with what. We could
bring a substitute on the market that can be worse than what we
replaced.
ANSWER (Mr. Manfer): That is a very good point. Let me put it this way.
I do not want to steal anybody's thunder tomorrow who is going to
be talking about this product, in particular. We belong to an
organization called TIMA, the Thermal Insulation Manufacturers
Association. For the last 20 years, they have been doing studies
on fiber glass and ceramic products. Ceramic fiber is not new;
it has been around since the early 1950's. So far, TIMA has not
shown any negative results from ceramic fiber. It is a smooth
fiber, it is not like asbestos, and it does not get caught in your
lungs; it can be expectorated. The fiber diameter is large enough,
usually, so that it gets stuck in your throat before it goes
down to the lungs.
Let me assure you that for the last 20 years TIMA has been working
with ceramic fiber and fiber glass materials and nothing has been
proven. It is difficult to prove a negative—we do not know what
will happen in the next 30 years—but for the last 20 years the
testing has shown no carcinogenic or ill effects.
QUESTION (Mr. Guy) : I am from the Weyhaeuser Company. We have a severe
problem with the door gasketing or door seals, under what I would
call high temperature applications for 500 to 600°F. Do you still
feel that there is an appropriate substitute material? We have
trouble with resiliency and, secondarily, with abrasion resistance.
The resiliency problem has not been satisfactorily solved with
either asbestos material or gasketing door seals, or with the re-
placement materials.
ANSWER (Mr. Manfer): I definitely think there is a replacement product,
and that is one of our best sellers. It is a ceramic rope that is
very resilient, in high temperature applications. I am not going
to say that I can come in and replace your rope tomorrow, nor will
the fiberglass, Siltemp, or aramid people, but we can work with you,
anybody can work with you, and over time, you will get a suitable
replacement.
QUESTION (Mr. Guy): Do you know if any of these substitutes are silicon-
based or have other kinds of internal structures to support them?
Or are they straight replacement material?
ANSWER (Mr. Manfer): It is hard to say they are straight replacements
because substitution occurs on a application-by-application
basis, I am not sure what you mean by silica support.
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ASBESTOS SUBSTITUTES IN ROOF COATINGS
by
Dr. Kenneth Brzozowski
Tremco, Inc.
Cleveland, Ohio
ABSTRACT
Asbestos is used in roofing products, and, to a lesser degree, in sealants
and caulks for the variety of properties it imparts to these products.
Specifically, asbestos is used for sag or flow control, reinforcement, coating
hold out, etc. A large number of substitutes have been proposed and offered.
None, however, have been found that duplicate the performance of asbestos.
The substitutes found most suitable are very costly. In some cases, they
are as much as twenty times more expensive.
As with other industries, the building waterproofing industry has been
concerned about a possible ban on the use of asbestos in its products.
Tremco, as I am sure many other companies marketing waterproofing materials,
has been very active in searching for and evaluating the dozens of asbestos
substitutes that are presently on the market. Very briefly, let me mention
some of the substitutes that have been offered to our industry:
Precipitated Calcium Carbonate
Ground Rice Hulls
Shredded Newspaper/Clay
Shredded Newspaper
Ground Fly Ash
Fumed Silica
Citrus Flour
Polyethylene Fibers
Fiberglass
Let me say at the outset that our search, though long and extensive, has not
been completely successful. We have not been able to uncover a material that
performs in a manner similar to asbestos. The primary problems that we have
encountered with substitutes are:
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1. Cost
2. Oil Absorption
3. Sag Resistance
4. Settling
5. Appearance of Product
COST
I will now give a few details on each of these problems. Our experience
is that asbestos replacements are priced anywhere from two to twenty times
higher than asbestos. Depending on the product the replacement is going into,
this translates into a finished cost of between 10 percent and 150 percent
higher. These higher costs would obviously have to affect the selling price
to the user or consumer.
OIL ABSORPTION
Oil absorption is the amount of oil required to wet or be absorbed by a
specific amount of pigment or filler - in this case asbestos or asbestos re-
placement. The higher the oil absorption of a filler used in a formulation,
the greater the viscosity of that coating or sealant or caulking material or
whatever. Our experience indicates that most of the substitutes now on the
market have lower oil absorption characteristics than asbestos. This means
more substitute must be used to achieve the same viscosity in a product. This
of course, relates to the cost considerations which I have already mentioned.
SAG RESISTANCE
Sag resistance is the tendency of an applied wet film of material to
remain stationary or resist excessive flow. For example, when you apply a
paint or caulking to a vertical surface, you want it to remain in place and
uniform on the wall or in the vertical joint. Again, we have found many of
the substitutes deficient in this property. Even, with very high loading,
i.e. large amounts of filler added to the formulation, we have been unable to
obtain acceptable sag resistance properties with these substitutes.
SETTLING
Settling is a term used to describe the process in which there is
separation of solid material from the vehicle to the bottom of the container.
Obviously, excessive settling, especially settling in a short period of time,
would make the product unusable. Most asbestos substitutes have not per-
formed well with regard to sag resistance.
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APPEARANCE OF PRODUCT
Our experience indicates that products "look" different when asbestos is
replaced. We do not view this to be a serious problem, but are cognizant of
the fact that our customers would have to be alerted of any change and re-
educated in the use of our products should asbestos be removed.
Turning from coating properties to safety considerations, we feel
comfortable with using asbestos in our products. Some time ago, we converted
to the use of compacted asbestos in our products to reduce the concentrations
of asbestos in the air when handling it in our plants. This required some
alterations in manufacturing procedures, but was a relatively straightforward
change. Further, we require that only whole bags of asbestos be used when a
batch of product is manufactured. This causes us to adjust batch sizes
to accommodate whole bags, but eliminates the hazard of having opened partially
filled bags laying around a plant. We also have installed highly efficient,
closed-system exhaust units in all our plants. Asbestos levels in our plants
are monitored by Tremco personnel and, in addition, we have outside testing
services check our results on a regular basis. Our air samples always indicate
that we are orders of magnitude below the maximum safe limits.
While our coating and caulking materials are being applied and when they
are in service, the asbestos is locked into the vehicle and presents no hazard.
Thus, from a safety point of view, we see no reason to place a ban on
asbestos in the type of products we manufacture.
Despite the technical problems I have mentioned and the lack of hazard we
perceive, we are very actively pursuing substitutes for asbestos or ways to
eliminate fillers altogether. This year, for example, Tremco introduced what
we believe is the first solvent-free asbestos-free roof rejuvenating coating.
We were able to accomplish this without a large increase in selling price and
without sacrificing performance. It is our intention to continue on this
path; namely introducing asbestos free products that perform as well or better
than present products with little or no increase ip cost. This will be
accomplished as our technology allows us and/or new raw materials become
available.
However, should a ban be placed on asbestos tomorrow, Tremco would not be
out of business. We have asbestos free formulations for all our present
products. These products would not perform as well as existing products and
would be more costly. Our chief concern is whether the suppliers of the
substitutes could produce the enormous amounts of material that would be
required if asbestos is banned.
To summarize:
1. We have been unable to discover a single fiber that can be used
across our product line as a substitute for asbestos.
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2. Formulating techniques and the use of several asbestos substitutes
have allowed us to develop product formulas which are asbestos free.
These products are inferior in performance and higher in cost when
compared to asbestos containing formulations.
3. We feel that asbestos, as presently used in our products, is safe.
4. Tremco is concerned that enough asbestos substitute materials would
be available if asbestos is totally banned. Especially since all
users would be competing for the best substitute materials.
5. Over a period of time, Tremco expects to phase asbestos out of its
products, but only as technology and raw materials become available.
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OVERVIEW OF ASBESTOS
SUBSTITUTES IN SEALANTS,
ROOF COATINGS AND CEMENTS
by
Mr. Eric Wormser
The Gibson-Romans Company
Twinsburg, Ohio
ABSTRACT
In spite of extensive research, the industry has not found a raw material that
is a satisfactory substitute for asbestos fibre in roof coatings and roof
cements. Complicated formulating techniques have been developed by isolated
manufacturers of roof coatings and cements that enables them to produce satis-
factory products without asbestos. These products are more expensive than
those containing asbestos and are of lesser quality. A ban in the near future
on asbestos fibre in roof coatings and cements would result in large volumes
of vastly inferior products being sold to the public, in the speaker's opinion.
The majority of caulks and sealants currently on the market do not contain
asbestos fibre. Reformulation of those caulks and sealants which do contain
asbestos fibre should not present a serious problem.
Dr. Brzozowski has given you a technical exposition into the current
state of asbestos fibre substitutes in roof coatings, roof cements and seal-
ants. I will give a non-technical overview in.to the situation. It will take
only one minute to discuss the problems of substituting for asbestos in seal-
ants. That is simple. I plan to use the remainder of my time to discuss with
you the far more serious and complicated problems of trying to eliminate
asbestos fibre in roof coating products.
We are not aware of any significant amounts of asbestos fibre being used
in calks and sealants. Mr. Gurtowski did mention some aircraft sealants where
asbestos so far has defied substitution. Caulks and sealants are liquid or
semi-liquid gap fillers used in building and equipment construction. They are
made from elastomers, synthetic or natural oils, bodied into suitable consis-
tency, which may be pourable but more often is much thicker. In our own com-
pany we still have a few specialized formulas containing asbestos fibre. In
the absence of regulations banning the use of asbestos in caulks and sealants,
we have customer resistance in a few cases to making the necessary changes in
properties and purchasing specifications, in order to use substitute materials,
However, should the use of asbestos fiber no longer be permitted in these
products, I do not foresee a serious problem in coming up with acceptable
formulas that do not utilize asbestos.
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Now let us turn our attention to roof coatings and cements. First I want
to explain the difference between these products. Roof coatings are cold
applied liquids that are used to rejuvenate and protect almost any type of
roof, except usually not the typical home shingle roof. Typical types of
buildings utilizing roof coatings are home garages, porch decks, apartment
houses, sheds, farm buildings, industrial buildings and commercial buildings
of all sorts, including stores, shopping centers and office buildings. These
coatings are applied by brush or spray.
Roof cements are trowel applied compounds. Their consistency is similar
to soft margarine. They are used to seal openings large enough so that liquid
coatings would run through them. Roof cements are used on almost every type
of building regardless of the roofing system employed, including the typical
shingle roofed home. They are used to seal between vertical and horizontal
surfaces and around projections such as vent pipes, chimneys, roof heating
and air conditioning units, gutters, and gravel stops, the list is almost
endless.
Approximately 65 percent of our company's sales of roof coatings and roof
cements go through retail stores to the homeowner and handyman type applicator.
The sheet roofing systems described by speakers are almost universally
applied by the professional roofer. Roof coatings and roof cements are used
to protect most of these systems also. I do not believe that anyone is
suggesting that sheet systems that do not contain asbestos can replace roof
coatings and roof cements. Should anyone entertain such an idea, a study of
the needs of the building owners will clearly show that roof coatings and
cements are necessary supplements to the roofing sheet systems.
Roof coatings are also used as waterproofing mastics on porous walls of
buildings, above and below ground - on surfaces such as concrete block, poured
concrete and brick. There are a number of types of roof coatings. By far
the largest segment of this business is in coatings consisting of asphalt
liquified with solvents and bodied with asbestos fibre. Once the asphalt is
liquified with solvents sufficiently so that it can be readily applied to the
surface without heating, the asbestos fibre is the vital ingredient for several
reasons. Without the asbestos, the liquified asphalt will penetrate entirely
into the surface it is supposed to rejuvenate, leaving little or no protec-
tive layer on top of the surface. On the type of surfaces where there is no
penetration, such as on metal, if there is a slope to the roof, the liquified
asphalt will sag or run in the absence of asbestos fibre. In addition, the
asbestos serves to reinforce the asphalt. After the solvents have evaporated,
the asbestos fibre prevents the asphalt from cracking as the surface moves
with expansion and contraction from temperature changes. A roof goes through
large temperature cycles in every 24 hour period. The asbestos fibre also
retards the oxidation and deterioration of the asphalt. This deterioration
results from severe exposure to the actinic rays of the sun that is typical
for roofs. Last but not least, in the event of fire, the asbestos fibre will
retard melting and running of the roof coating.
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So far no single raw material has been found that will replace the func-
tions performed by asbestos fibre in solvent thinned asphalt roof coatings.
There is a variety of other types of roof coatings sold. Their total volume
is far less than the asphalt solvent coatings, so far as asbestos is used,
are at least to a degree similar to those described for the asphalt solvent
coatings.
As mentioned earlier, large quantities of roof cements are used in addi-
tion to the coatings. As already mentioned, almost without exception, no
matter how a roof is originally constructed or later repaired, these trowel
consistency cements are utilized in that construction and repair. These
cements commonly are solvent thinned asphalt or coal tar bodied into a heavy
consistency with asbestos and other mineral fillers.
To date no raw material has been found to equal the properties of asbes-
tos fibre in achieving the needed body. To perform their function these
cements must be suitable for troweling and at the same time must contain
enough bitumen after evaporation of the solvents to deposit a thick film on
the roof surface that has good weathering integrity.
The industry has had a strong incentive to find a way to manufacture roof
coatings and roof cements without asbestos fibre. Consequently a tremendous
amount of work has been done. One aspect of this incentive has been the
tightening regulations by EPA and OSHA and the threat of regulations that
would make it impractical to continue to use asbestos. Another incentive has
been pressure from customers who prefer not to sell or use products that con-
tain asbestos because of the large volume of bad publicity surrounding it..
The greatest incentive, however, that the industry has had to formulate around
asbestos is the recurring disruptions in asbestos supply that we have exper-
ienced in recent years. Over the last 5 years our purchasing staff has spent
more time fighting to get enough asbestos to keep our plants running than any
other single raw material. We have vowed to get away from the use of asbestos
because we cannot afford to be as dependent upon a raw material as we are on
asbestos, when it seems every other year or so there is a critical shortage.
In spite of the tremendous amount of work that has been done to try to
find a substitute raw material that will produce satisfactory roof coatings
and roof cements, to the best of our knowledge no one has found such a material.
As the result of our company's vast research, by complicated formulating tech-
niques, utilizing a variety of ingredients and techniques, we are now able to
produce solvent base asphalt roof coatings and roof cements that do an adequate
job without asbestos fibre. We assume that there are some other manufacturers
in a similar position. We do not yet offer these asbestos free roof coatings
and cements for sale in the United States because they are about 15 percent
more expensive to produce and we believe they are not as good as comparable
products made with asbestos. It is difficult to justify selling an inferior
product for more money. We are shipping considerable quantities of asbestos
free coatings and cements to Sweden, where the use of asbestos fibre in such
products has been banned. Therefore, we are gaining experience in the volume
manufacture of such products and have the opportunity to observe their per-
formance in large scale use.
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We feel strongly that a ban in our country on the use of asbestos fibre
in roof coatings and cements would be profitable to our company because we
could furnish our customers workable products whereas most of our competitors
could not. At the same time, we feel that such a ban would be a great dis-
service to the American public. In view of the stringent OSHA requirements
for handling of asbestos fibre in the manufacture, and EPA requirements for
disposing of wastes, no one is being injured by the use of asbestos in our
plants. Once the asbestos is bound in the roof coating and cement vehicles,
it can do no harm to anyone. Therefore, a ban would not benefit anyone. On
the other hand, it would force on the American public a flood of very poor
products at high prices.
Let me explain why it has not been possible to make roof coatings and
cements of equal quality with substitute raw materials. Asbestos fibre is
unique among known raw materials in that it is a completely inert, indestruc-
tible mineral that can be processed into a fibre. This fibre partially
absorbs the vehicle into which it is placed and becomes an integral part of
that vehicle, without settling or floating. Small amounts of asbestos fibre
add a large degree of body to the vehicle, so that relatively small amounts
of asbestos turn a thin liquid into a consistency akin to apple-butter. What
other inert inorganic fibres are there? Very few. Glass is completely un-
absorptive. Therefore it is not possible to make a homogeneous coating out
of a vehicle with glass fibre. Glass fibre floats in roof coating vehicles,
unless it is held down with something else. As a matter of fact, we make
some glass fibre roof coatings and cements and we hold down the glass with
asbestos fibre. There is a rock wool. In our experience it does not have
the absorption properties that will permit a homogenous mixture. Fibrous
talcs, wollastonites, ceramics and clays are not fibrous enough to duplicate
the performance of asbestos. Most other fibres that are available are organic
in nature. They melt, they deteriorate on ageing and most have poor chemical
resistance.
Although we do not know of a fibre that can be satisfactorily substituted
for asbestos in the manufacture of roof coatings and roof cements, nothing is
impossible. We consider it unlikely however that such a fibre will be found
in the foreseeable future. The only method we know for manufacturing reasonably
satisfactory asbestos free roof coatings and roof cements is to combine some
less than satisfactory substitute fibres with a variety of mineral fillers,
wetting agents, plasticizers and synthetic thixotropes. We manufacture about
250 different roof coatings, cements and mastics. A variety of techniques
must be used to achieve acceptable results in each of these products. The
end result in every case is a product that contains considerably less asphalt,
tar or other water proofing oil and much more filler material than when asbes-
tos is used. These fillers contribute nothing to the waterproofing properties
or weathering of the products. To the contrary, these filler materials often
detract from the desirable properties. These formulas require from 30 to 70
percent more energy in our plants to manufacture.
There are Federal Specifications covering asphalt roof coatings and roof
cements. Although we have developed asbestos free formulas which we feel are
of acceptable quality, they do not meet the standards in the Federal Specifi-
cations. In every case the asbestos free formulas exceed the maximum filler
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content permitted by these specifications. The writers of these specifications
rightfully specify a minimum ash content for the fillers that are used. These
we are also unable to meet with our asbestos free formulas. At the present
state of the art, the General Services Administration would have to lower its
purchasing standards for asphalt roof coatings and cements, as would the
non-government buyer, in order to utilize asbestos free products.
I need to explain to you my statement that if the use of asbestos fibre
in roof coatings and cements was banned, the market would be flooded with
very poor products, so poor as a matter of fact that they would be virtually
useless. Our company currently ships over twenty million gallons of roof
coatings per year. We believe we are the largest manufacturer of roof coatings
in the world. Most of our "competitors ship two to five million gallons. These
competitors cannot afford the research we have spent on developing asbestos
free formulas or the dollars that we will continue to commit to this project.
Relatively few of our competitors in the roof coating business even have
laboratories. In any typical asbestos free formula, there is no one raw
material that represents sufficient volume so that it is really worthwhile
for raw material suppliers to do adequate research. Raw material suppliers
have touted numerous suggested asbestos free formulas, none of which will
make a satisfactory product. During recurring periods of asbestos fibre
shortages we have seen examples of the type of products that some of our com-
petitors have shipped in desperation. Their only choice was to close their
doors because they could not get asbestos or ship the best they could make
without. What they shipped was a disaster. These events bring us to the
strong belief that should there be an asbestos ban, in order to stay in business,
the numerous small competitors will be forced to ship products that are a dis-
service to the industry and the user.
Another aspect needs to be considered. The hazards of asbestos fibre
have been thoroughly researched and documented. They are real but readily
controllable and limited. We know little or nothing about the hazards of the
variety of raw materials we use in order to manufacture asbestos free roof
coatings and cements. We get material safety data sheets from our suppliers.
None of the new raw materials are known carcinogens.. It is unlikely, how-
ever, that anywhere near the amount of research into the health hazards of
these materials has been devoted as has been to asbestos. You will, during
this workshop, get a health report on only some of the alternate materials
that may be used in asbestos free coatings.
The supply picture of the combination of materials needed to make asbestos
free coatings must also be taken into account. Several of the raw materials
are highly specialized and produced in small volumes. We have determined on
some of the materials that the supply is far short of what we would need if
our company converted its entire production to asbestos free coatings and
cements. We have not investigated whether it is possible to expand the supply
in every case to that which would be needed to cover the entire industry. I
would assume that given time and sufficient demand a way can be found to supply
the needs of the industry with these materials. However, if there should be
a sudden ban on the use of asbestos fibre in roof coatings and cements, the
available raw material supply would not meet the demand from our company, to
say nothing of meeting the industry's demand should other manufacturers want
to use the same methods.
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TO SUMMARIZE
1. There are a number of types of roof coatings and roof cements.
2. The predominant type that is sold is solvent base asphalt roof
coating and roof cement.
3. We do not know of a substitute for asbestos fibre in these products
nor in any other type of roof coating.
4. We can make asbestos free solvent base roof coatings and cements
by complicated formulating techniques.
5. We believe our company would benefit from a ban on asbestos in
roof coatings and cements.
6. Such asbestos free products are more expensive than those containing
asbestos fibre and we believe inferior in quality. They do not
meet existing Federal Specifications.
7. I do not foresee a change in this picture in the foreseeable
future.
8. Little is known about the health hazards of some of the raw materials
we would use in order to produce asbestos free coatings and cements.
9. The supply of some of the raw materials we would use is inadequate
to meet our company's requirements to say nothing of industry
needs.
10. If asbestos were banned in roof coatings and roof cements, in my
opinion, the market would be flooded with products so inferior in
quality that they cannot perform the purpose for which they are
intended.
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QUESTION
DISCUSSION ON SEALANTS
(Chairman Guimond): I have a question for Mr. Wormser. You men-
tioned the Federal specifications that require, I think you have
indicated it was ash content. Someone yesterday mentioned to me
that a certain Federal specification, SSC-153-C, actually speci-
fies required amounts of asbestos.
ANSWER
QUESTION
(Mr. Wormser): That is correct.
specifies asbestos.
That specification actually
ANSWER
ANSWER
(Chairman Guimond): Is that frequent in specifications to actually
specify that you must have X percent of asbestos or it must con-
tain asbestos or contain certain other materials as opposed to a
specific performance?
(Mr. Wormser): I think there are other specifications that do specify
asbestos. Possibly Dr. Brzozowski is more familiar with the details
of the specifications.
(Dr. Brzozowski): I could not give you the exact number, but many
of the Federal specifications for roof coatings require asbestos
in the material.
QUESTION (Chairman Guimond): As a consequence, I would gather that to be a
very strong hindrance at the present time for you to be able to sell
roof coatings not containing asbestos to the Federal government?
ANSWER (Mr. Wormser): I would say until the Federal government changes their
specifications we would not be able to provide them with roof
coatings and roof cements.
REMARK (Mr. Hughes): I have a comment that is prompted by Mr. Wormser's
observation about the effects of recurring shortages of fiber.
I think this is one of the often unrecognized forces that asbestos
regulation is imposing on the industry. The fact is that there
has been no investment in new asbestos fiber production capacities
except in the Soviet Union. The reason is simply because of the
very hostile regulatory attitude that prevails in the United States
and in some other countries. It is very difficult to justify in-
vestment and yet we see these recurring shortages. It imposes
substantial costs on the consuming industry and it is a direct re-
sult of regulatory actions.
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GLASS FIBER REINFORCED CEMENT
by
Mr. John Jones*
Cem-FIL Corporation
Nashville, Tennessee
and
Mr. Frank W. Fekete
GRC Products, Incorporated
Schertz, Texas
ABSTRACT
The paper will present physical properties and characteristics of glass fiber
reinforced cement (GRC) and how these are affected by different composite formu-
lations. In addition, it will discuss the various processes for manufacturing
GRC and how these affect the characteristics of GRC. A comparison with asbes-
tos-cement and other possible substitutes will be made throughout the paper.
Both the' economics of•GRC versus asbestos-cement and several applications where
GRC has been adopted as a substitute will be discussed.
INTRODUCTION
Glassfiber reinforced cement (GRC) is basically a composite of a hydraulic
binder, such as portland cement, reinforced with glass fibers, with or without
fillers or additives. In this respect it is similar to asbestos-cement with
glassfibers as the reinforcing agent instead of asbestos fibers. Like asbestos-
cement, GRC is not just one material but is a whole spectrum of composites each
with different performance characteristics depending on factors such as the type
of cement used, glassfiber content, type and quantity of filler and/or additive,
and the density of the composite.
Although GRC has many possible formulations, the predominant basic compo-
site is based on portland cement with an inert filler such as sand or limestone
fines and reinforced with a special alkali resistant glassfiber. Much of this
paper discusses this particular type of GRC and it will be referred to as high
density GRC.
*Presented by Mr. John Jones.
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PROPERTIES
Figure 1 gives the basic physical properties of GRC containing 5 percent
by weight alkali resistant glassfiber. These are compared with manufacturers'
data for asbestos-cement.
GRC has properties similar to those of asbestos-cement with one notable
exception: impact strength, in which GRC is approximately ten times stronger
than asbestos-cement.
Although original formulations of GRC lost a significant amount of this
high impact strength over a period of a few years under natural weathering con-
ditions, the long term impact strength was still higher than that of asbestos-
cement. However, recent improvements in alkali resistant glassfiber have sig-
nificantly improved long term durability. Figure 2 illustrates the magnitude
of this improvement in the retention of the area under the stress-strain curve,
a measure of the impact and abuse-resistance of the material.
All GRC formulations will satisfy ASTM 136 as regards non-combustibility
and will be rated 0 on all characteristics measured by ASTM E84. However, high
density GRC (like asbestos-cement) can explosively spall when subjected to very
rapid temperature rise as experienced under fire conditions.
Some characteristics of GRC can be changed by changing its formulation.
Thejmal insulation, fire performance, and high temperature performances are
three such properties.
The use of perlite (or a similar lightweight filler) can reduce the density
by up to 50 per cent. The effect of reducing density on properties such as
thermal insulation can be seen in Figure 3. Also, these formulations provide
GRC products with excellent fire resistance properties. Figure 4 shows the
fire ratings achieved for different thicknesses of sheet with a density of
approximately 62 Ibs. per cu. ft. During the tests the sheets showed not only
excellent fire resistance, but showed no tendency to spall or crack even after
the fire test was stopped and the sheet cooled down.
GRC based on portland cement can be formulated to have good fire resistance
properties and satisfactory performance at high temperatures for a short period
of time. However, these composites do not usually perform well under prolonged
exposure at elevated temperatures, unlike asbestos-cement which performs well
up to 600°F and in some cases higher. However, recent lab tests and product
field trials have shown that GRC based on high alumina cements and reinforced
with alkali resistant glassfiber will perform well certainly up to 600°F, and
some recent results suggest possibly up to 1000°F.
Although these GRC composites under prolonged exposure at elevated tempera-
ture lose some strength and embrittlement is evident, comparative tests against
asbestos-cement have showed that high alumina GRC performs in actual service at
least as well as asbestos-cement.
Some areas where high alumina GRC has been compared favorably with asbestos-
cement are in furnaces and ovens, and in high temperature electrical equipment.
122
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FIGURE 1
Physical and Thermal Properties
of
Asbestos-Cement Board
and
High Density Glassfiber Reinforced Cement Board
*ACB GRC
Dry Density, Ibs. per cu. ft. 100 123 to 128
Moisture Content
(% of Dry Weight) 5 to 13 2 to 8
Water Absorption
(% of Dry Weight) 22 (48 hrs.) 5-10 (24 hrs.)
6
Modulus of Elasticity psi x 10 1.5 2.4
Compressive Strength, psi 12,000 10,000 - 16,000
Tensile Strength, psi 1,400 1,600 - 2,200
Transverse Strength, psi 4,000 3,300 - 4,000
Shear Strength, psi 3,500 5,300 - 7,200
Brinnell Hardness 25 29
Thermal Expansion, In/In/°F x 10"6 5.0 1.3 to 7
Dimensional Change Due to
Moisture, In/In
Shrinkage (Normal to Dry) 0.0020 0.0014
Expansion (Normal to 90% RLF) 0.0006 0.0004
Expansion (Normal to Saturated) 0.0028 0.0015
Maximum Service Temperature, OF 600 600
Surface Burning, ASTM E-84 0-0-0 0-0-0
Permeance, Perms 12 Less than 2
Freeze-Thaw Resistance Satisfactory Satisfactory
Thermal Conductivity,
BTU/In/Sq.Ft./Hr/°F 4 5
Impact (Falling Ball),
Energy Absorption, ft. Ibs. 18 229
*The data for ACS are taken from the literature of ACS suppliers.
123
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FIGURE 2
Flexural Stress-Strain After the
Equivalent of 30 Years Weathering
IMPROVED GLASSFIBER
ORIGINAL GLASSFIBER
0.5
PERCENT STRAIN
124
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FIGURE 3
Comparative Properties
of
Low and High Density GRC Sheet
Density, Ibs. per cu. ft. 125 62
Modulus of Rupture, psi 4000 2000
Water Absorption 16 22
(Max. % of Dry Wt.)
Thermal Conductivity 5.0 2.0
(BTU/In./Ft.2/Hr./°F
Maximum Service Temperature, °F 600 600
FIGURE 4
Results of Fire Tests
Conducted on Low Density GRC
Thickness ,
In.
0.688
1.181
3.076
Unit
Weight ,
pcf
**
78.4
73.6
Relative
Humidity
Per Cent
38
72
73
Fire
Endurance*,
hr:min
0:18
0.58
5.35
*Determined by the ASTM El19-79 criteria for temperature rise
of the unexposed surface.
**Not weighed.
125
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Although 6RC can often offer comparable performance to asbestos-cement,
it is not an exact replacement. For instance, the physical appearance of GRC
sheet is not yet as good as asbestos-cement in either surface smoothness or
thickness uniformity (process developments in progress are expected to correct
this). GRC sheet, although it cuts as easily as asbestos-cement, does not fabri-
cate as neatly in that there is more chipping and break-out around the cut edge.
MANUFACTURE OF GRC
The primary process that has been developed for GRC manufacture is based
upon a spray concept in which the cement slurry is pumped to a nozzle through
which it is atomized into a spray cone. Simultaneously glassfiber roving is
chopped, usually to a length from 1 to 2 inches, and the chopped strands are
blown into the cement slurry spray.
In small to medium scale production the spray-gun can be held by an opera-
tor, but more commonly it is mounted on a simple traverse mechanism which re-
ciprocates back and forth. The spray is deposited either into a mold or onto
a dewatering table (the purpose of dewatering is to extract the excess water
and compact the sheet).
Such a spray dewatering machine is used by Cem-FIL Corporation (Nashville,
Tennessee) for flat and corrugated sheet manufacture. Where much higher volumes
are required, equipment has been developed that can produce several million
square feet per year. GRC Products, Inc. (Schertz, Texas) is commercially op-
erating such a facility.
Progress has been made in developing techniques to manufacture GRC sheet
on the Hatschek process that is used for asbestos-cement production. GRC sheet
made by this method has a modulus of rupture of about half that of asbestos-
cement sheet, but has been used successfully as a substitute in several
applications.
ECONOMICS
The manufacturing cost of GRC is quite dependent on the scale of manufac-
ture. GRC sheets made on the medium volume process described above are about
two to two and a half times the price of asbestos-cement sheet. Where the
high volume process or the Hatschek process is operated, GRC costs are around
50 percent higher than asbestos-cement. When GRC manufacture becomes more com-
parable with the scale of asbestos-cement manufacture, the price differential
could well be reduced to 20 percent or less.
At the moment, 1/4 inch thick GRC sheet is available at about 80
-------
A full range of flat sheets from 1/8 inch through to 4 inch thick is
available from inventory in 4 ft. by 8 ft. sheets. Standard 4 ft. by 10 ft.
sheets are available in thinner sheets between 1/8 inch and 3/8 inch. Corru-
gated sheets in the standard 4.2 inch pitch are also available.
Where high temperature performance or fire protection is required, two
grades of flat sheet are in the advanced stage of field trials and are avail-
able for product performance trials.
APPLICATIONS
Pullman Standard Company has used 1/4 inch thick GRC sheet as the replace-
ment for asbestos-cement sheet in the lining of electrical closets in Amtrak
passenger cars. Amtrak also uses GRC sheet for the same purpose. In this use
the asbestos-cement provided both fire resistant lining and some thermal insula-
tion so that if a fire were to occur in the closet, the lining would protect the
steel stairway from the upper deck for a sufficient time to allow passengers to
escape. GRC sheet was the only substitute that offered the same fire resistance
performance as asbestos-cement. Although the thermal conductivity of high den-
sity GRC is slightly higher than asbestos-cement, it was satisfactory for the
purpose.
E. I. Dupont uses both flat GRC sheet and corrugated sheet as replacements
for asbestos-cement. The corrugated sheet is used for repair and maintenance
of existing asbestos-cement clad buildings, and for new construction. Flat
sheet is used for a variety of uses within the plants, particularly fire resis-
tant linings and partitions.
Several manufacturers are testing GRC sheet as fume hood linings and one
company has already started to utilize it in their range of hoods. GRC offers
the same chemical resistance as asbestos-cement, being resistant to most chemi-
cals except strong inorganic acids.
The heat resistant grade of GRC has been extensively tested by a variety
of oven and furnace manufacturers. In particular, several manufacturers of
pizza ovens have approved its use as a substitute for shelves and linings.
GRC sheet, both flat and corrugated, has been used on a limited scale in
cooling towers. Flat sheet has been substituted for asbestos-cement in cell
partitions and fan decking and corrugated sheet has been used for louvers and
end-wall and stairwell casings. GRC has demonstrated the same excellent dura-
bility and rot resistance as asbestos-cement under the extreme conditions that
exist in cooling towers.
GRC has been used in a wide range of building uses, particularly architec-
tural panels. Wide use is now made of GRC in custom-molded claddings and in-
creasing use is being made of flat GRC sheet in spandrel, soffit, and fascia
panels.
GRC is being evaluated as a substitute for asbestos-cement in light duty
waterfront bulkheading on canals, inlets and estuaries. GRC corrugated sheet-
ing will probably be approved for this use, since load tests and field trails
have demonstrated its structural suitability.
127
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CONCLUSIONS
GRC is not a development material, but in fact, has been in use for over
18 years. Although some of the products are going through evaluation trials,
the basic material is backed by years of service use as well as by extensive
laboratory testing.
Some of the technology for high volume sheet manufacture is new, but pro-
ducts made on such processes are readily available and are being sold and used
commercially.
The principal reason that GRC is proving to be the most widely used mater-
ial as a general substitute for asbestos-cement sheet is that it has the same
excellent general properties, such as good mechanical strength, good chemical
resistance, rot proofness, fire resistance, heat resistance, and the ability
to be simply machined and fabricated.
Although many materials may be superior in any one of these characterise
tics, only GRC is like asbestos-cement in that it offers an excellent balance
of all these features.
Although GRC is at the moment more expensive than asbestos-cement, there
is no doubt that with continued and increasing scale of use over the next few
years, the price differential will shrink considerably, and quite possibly could
disappear completely.
128
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OTHER SUBSTITUTES FOR ASBESTOS-CEMENT SHEET
by
Dr. David Cogley
GCA Corporation
Bedford, Massachusetts
ABSTRACT
Asbestos-cement sheet is defined in terms of special qualities imparted by
asbestos. Market share is discussed for the four basic forms of asbestos-
cement sheet: flat sheet, corrugated sheet, siding shingles, and roofing
shingles. Both product substitutes and fiber-for-fiber replacements are con-
sidered for low temperature and high temperature applications. Substitute
products include cement/wood board, mineral insulating boards, aluminum sheet,
wood, and brick. Each product alternative is discussed in detail including
product manufacture, composition, durability, life, cost, and market trends.
A wide variety of substitute products are available for most asbestos-cement
sheet applications.
Asbestos-cement (A/C) sheet products have been used for many years in the
United States. I will briefly describe the variety of A/C products available,
their uses, and special properties. Substitute products suitable for some A/C
product applications will be discussed. Included will be comparisons of com-
position, strength and durability, cost, life expectancies and market trends.
Asbestos-cement sheet products represent about 6 percent of the total
amount of asbestos used in the United States annually. Although used mainly
in construction applications such as roofing and siding for both industrial
and residential buildings, it is also an ingredient in the manufacture of
heaters, boilers, vaults and safes, electrical equipment mounting panels,
welding shields, and many other products where a noncombustible or heat-
resistant sheet is required.
Asbestos has become important as a reinforcing agent due to its avail-
ability, price and unique combination of the following properties:
• tensile strength
• flexibility
• resistance to heat
• chemical inertness and
• large aspect ratio. 129
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Asbestos fibers in cement sheet add to the strength, stiffness and tough-
ness of the material, resulting in a product that is rigid; durable; noncom-
bustible; resistant to heat, weather, and attack by corrosive chemicals; and,
in addition, stable. A significant feature of A/C sheet is that it possesses
sufficient wet strength to enable it to be molded into complex shapes at the
end of the production process.2 As a result, A/C sheet can be found in four
basic forms:
• flat sheet
• corrugated sheet
• siding shingles, and
• roofing shingles.
Substitutes are being sought for a wide variety of A/C sheet products.
For flat sheet, the applications range from internal and external paneling,
decorative paneling, cooling tower fill, fume hoods, and thermal and fire pro-
tection walls, to electrical equipment mounting panels. For each of these
applications, performance requirements vary and it is to be expected that
several different substitute products will be required. Corrugated sheet is
used primarily as a construction material where the additional strength afforded
by corrugation is of benefit. Siding shingles constitute a single product class
with performance requirements expected to vary according to the geographic loca-
tion of product use. Similar remarks apply to roofing shingles.
Among the properties that may be important for any particular application
of A/C sheet, one may consider the following:
• physical strength
• fracture toughness
• high temperature performance
• electrical conductivity
• resistance to moisture
• resistance to freeze/thaw cycle, and
• overall weather resistance.
Of two possible ways of evaluating performance, that is performance specifica-
tions or use specifications, we have chosen use specifications. This is con-
sistent with the experience of industrial manufacturers as well as standard
setting organizations such as ASTM (The American Society for Testing and
Materials). Just as special formulations are employed to achieve optimal
performance of A/C products, it is to be expected that special formulations
and product development efforts will be required for substitute products. For
many if not most of the substitute products to be discussed today, this fine
tuning stage has yet to be reached. Results to date show promise but as we
heard for friction products, further development effort will be required
before economically viable substitutes for all A/C sheet applications become
a reality. Substitutes for A/C sheet include:
130
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• housing materials such as wood shingles, stucco, concrete block,
brick, unreinforced cement shingles and asphalt shingles;
• laminated hardboard (Benelex)
• cement/wood board
• polypropylene layered cement sheet
• insulating boards (such as Monolux)
• alumina sheets (Alumina-sheet), and
• glass-reinforced cement sheet, which was discussed by John Jones.
Masonry, galvanized steel, reinforced plastics, and wood can also compete in
certain situations. This paper concerns itself mainly with product replace-
ments not fiber replacements.
Brief descriptions of composition and manufacturing methods are provided
for seven substitute products. These descriptions are followed by a discussion
of limitations of substitute product uses.
Laminated hardboard, such as Benelex, is made from wood. Wood chips are
first reduced to fibers by a steam explosion process. The unwanted elements
in the wood are driven off, leaving cellulose fibers and lignin, a natural
bonding agent. The fiber is refined and then formed into panels. It is cur-
rently manufactured by Masonite Corporation of Michigan.3
Cement/wood board can be used as an alternative to A/C sheet in some flat
sheet applications. It is composed of specially treated wood fibers bound with
Portland cement. This board will soon be produced by The International Housing
Corporation of California. To make cement/wood board, wood fibers are treated
with various chemicals including ammonium chloride, sodium chloride, and sodium
silicate in a process called "mineralization" to remove the resins, acids, and
sugars present in the wood. These treated fibers are combined with cement to
form cement wood board.
Polypropylene cement sheet is manufactured by Conwed Corporation of St.
Paul, Minnesota. Details of its manufacture are not available.
Insulating board products such as Monolux are made of calcium silicate
cement and selected fillers, reinforced with alkali-resistant glass and wood
fibers. Monolux is currently made in England by Cape Boards and Panels, Ltd.,
and marketed in the United States by W. B. Arnold & Company.4
Alumina-Sheet is over 90 percent alumina with about 8 percent silica
fibers. Zircar Products, Incorporated, of New York now manufactures this
product. It was developed as an asbestos board replacement for certain uses
and is suited for a wide range of high temperature, high thermal shock
applications.5*6
131
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8
Roof tiles, such as Monray by Monier Company of California, consist
mainly of Portland cement, sand, and water. The desired color is sprayed on
near the end of the production process.7
Roofing shingles such as CeDurShake are made of fiberglass-reinforced
polyester resin. They are currently produced by Trim Products of California.
The suitability of substitute products for specific uses is described
next. Some products have a narrow range of applications, whereas others such
as glass reinforced cement, discussed previously, are suitable for many prod-
uct applications.
The laminated hardboard product Benelex is used for laboratory table tops,
for floors of locomotives and cabooses, and as a phase barrier in electrical
switchgear and control apparatus. Laminated hardboards such as this could
replace ebonized asbestos in many electrical applications.3 Benelex is not
intended for products requiring resistance to weather or high temperature.
An alternative product such as cement/wood board is claimed to combine
the best properties of wood and cement. It is rated noncombustible and is said
by some to be virtually impervious to weather. Its modulus of rupture and
resistance to impact are greater than A/C sheet and, unlike A/C sheet, it can
be glued and laminated. Cement/wood board has good heat and sound insulating
properties, is easily machined, and has surfaces suitable for multi-purpose
treatment. It also has good elastic properties under a static load. Applica-
tions include: external claddings, sound attenuating walls, balcony parapets
and floors, walls separating gardens, partitions, noncombustible wall and
ceiling linings, roof soffits, refuse shafts, ceilings, fascia, and farm stable
linings. It has also been used to build prefabricated houses and pavilions.9
Participants at the A/C sheet round table discussion have indi-
cated that at least the cement/wood board products manufactured in Europe
during World War II showed poor resistance to weather. They indicated further
that cement/wood board is susceptible to excessive expansion due to absorption
of water by the wood component during wet weather. It is thus thought by some
not to be suitable for exterior cladding. Several means of combatting this
tendency to swell cost might thereby be increased. These potential corrective
measures include: saturation of the wood component with resin, painting, use
of special fasteners to allow expansion of sheet products without fracture,
or incorporation of 3-5% mica to reduce expansion.
Polypropylene cement sheet is a type of plastic cement board displaying
flexibility and good resistant properties. This product is comparable to A/C
sheet in its resistance to freezing, thawing, combustability, and aging.
Since it is a type of plastic cement board it is flexible and will not fracture
as easily as A/C sheet. It is used for construction of cooling tower spray
baffles, buildings, and other large structures.10
Monolux is a non-conbustible industrial insulating board which is rigid,
non-friable, durable, inert, and resistant to attack by insects and vermin.
The board is non-caustic, and unaffected by dilute acids and alkalis, brine,
chloride, or volatile solvents. It will not disintegrate, warp, or swell under
132
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prolonged immersion in water and is more resistant to heat than A/C sheet.
It can be used to make small ovens and dryers, high temperature ducts, oven
shelves and interleaves, and as secondary insulation for furnaces and kilns.1*
The alumina-silica product called Alumina-Sheet also exceeds A/C sheet's
resistance to heat. Available in either a moldable or rigid form, it is
being used as an insulator in induction core applications, as a molten metal
transport trough, and as a material for repairing holes in furnaces. In
addition, the possibility of using Alumina-Sheet for laboratory table tops
exists. Although not as strong as A/C sheet, its upper temperature limit
is several times greater. It is very tough and abrasion resistant.5*6
When comparing cost, the products mentioned vary from being quite a bit
less expensive than A/C sheet to being 10 times as costly1*"6'9'11'12. Accord-
ing to a product cost comparison between cement/wood board and A/C sheet done
by the cement/wood board manufacturer, the most expensive mill price of cement/
wood board is less than half the cost of Johns-Manville Flexboard A/C sheet
and less than one-fourth the price of J/M transite A/C sheet. Alumina-Sheet
is more than 10 times as expensive as transite, but the price is expected to
be cut in half as production increases this year.5
Steel is less expensive than A/C sheet and aluminum is competitive.13
Monier Monray roof tile and CeDurShake roofing shingles cost between $100-$130
for an installed square (a one hundred square foot roof surface), about the
same as Supradur A/C shingles.8'9
Availability of the substitutes covered here is also a critical factor in
their use. Substitute products have already been developed to suit most
applications formerly held by A/C sheet. A product such as cement/wood board
has been in use in Europe and the Middle East as an all-purpose building board
for a number of years.9 Most others discussed are currently in the market-
place. Unlike other industries now using asbestos which have embarked on a
series of research and development programs to find alternative nonasbestos
products, the A/C sheet industry has already identified and put into production
substitute products with new, nonasbestos formulations which in some cases
exhibit better performance characteristics.
In summary, A/C sheet was first used in the early 1900's; substitutes to
this product have generally only been developed recently, although, in some
applications, materials such as wood and masonry have always been available;
newer substitute products are available and appear to function well in place
of A/C sheet, but lack the advantage of being time-proven. In general, how-
ever, a variety of products incorporating the qualities of A/C sheet at a
competitive price are available as substitutes for A/C sheet in many of its
present applications. It is expected that further product development work
will produce viable substitutes for the remaining applications.
REFERENCES
1. Cogley, D. C., and N. K. Roy, et al. Asbestos Substitute Performance
Analysis. Draft Report. U.S. Environmental Protection Agency, Office
of Pesticides and Toxic Substances, Washington, D.C. March 1980.
133
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2. Pye, A. M. A Review of Asbestos Substitute Materials in Industrial
Applications. Journal of Hazardous Materials (Amsterdam). 3:125-147.
1979.
3. International Housing Corporation. Notebook containing information
about Cement/Wood Board. Sacramento, California. 1979.
4. Telecon, Swanson, C. Manager, New Applications Division, Conwed Corpora-
tion, St. Paul, MN with P. McGlew, GCA Corporation, CCA/Technology
Division, June 23, 1980.
5. Cape Boards and Panels, Ltd. Monolux Industrial Handbook. M1077914.
Uxbridge, England.
6. Telecon, Hamling, C., Zircar Products, Inc. Florida, New York.
\
7. Telecon, Porter, Jr., S. Marketing Assistant, Monier Company, Orange,
CA, with S. Duletsky, GCA Corp./Technology Division. February 15,
1980.
8. Smaus, R. Roofing Reaches New Heights. Home, a supplement of the
Los Angeles Times. January 27, 1980. pp. 8-11.
9. International Housing Corporation. Notebook containing information
about Cement/Wood Board. Sacramento, California. 1979.
10. Telecon, Swanson, C., Manager, New Applications Division, Conwed
Corporation, St. Paul, MN with P. McGlew, GCA Corp./Technology Division,
June 23, 1980.
11. Telecon. Lewis, W.H., GRC Products, Inc., Schertz, TX, with
S. Duletsky, GCA Corp./Technology Div., February 11, 1980.
12. Telecon. Bostian, J., Asbestos Fabrications, Inc., Charlotte, NC
with S. Duletsky, GCA Corp./Technology Division, March 7. 1980.
13. Weston, Roy F., Environmental Consultants, Technological Feasibility
and Economic Impact of OSHA Proposed Revision to the Asbestos Standard
(Construction Excluded). Asbestos Information Association/North
America. March 26, 1976.
134
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DISCUSSION ON SUBSTITUTES FOR ASBESTOS-CEMENT SHEET
QUESTION (Mr. Singe): I have a question for Mr. Jones. I am an architect with
the Navy Public Works Center in San Francisco.
Since Johns-Manville apparently has gone out of the AC sheet produc-
tion, at least on the West Coast, we have been unable to obtain either
corrugated or flat sheet. When you say that your product has a stan-
dard U.S. corrugation could I conveniently slip it into an existing
transite corrugated wall?
ANSWER (Mr. Jones): When I say the standard U.S. corrugation, I mean that the
corrugated sheet has been basically produced by the asbestos industry
has been 4.2 wave length. In that respect it is the same as the sheet
you used. However, before we could decide whether you could just fit
it in, we would have to check out the wind loadings to make sure that
you had adequate support there. As I said, you cannot necessarily
always substitute thickness for thickness. But certainly it is a very
easy thing to do. It is a I- or 10-minute job just to check that out.
QUESTION (Mr. Singe): My second question is, and it is also meant as food for
thought for the EPA, in a lot of products like pipe installation,
like your corrugated sheet, we have a product that is very similar
to the former asbestos-containing product. Our construction workers
often cannot tell the difference between a newer product containing no
asbestos and the former product containing asbestos, so they treat
everything as containing asbestos; thereby, costing us a lot of money,
and costing the taxpayer a lot of money because asbestos-containing
sheet requires special handling. I would like to see a product like
yours, if it is used for replacement of AC sheet, stamped or labeled
or somehow coded on the back as containing no asbestos so we know
what would require special handling and what does not require special
handling.
ANSWER (Mr. Jones): We do this when we send out a pallet of sheet. The shroud
that goes on the pallet does have a stamp on it that says it is
asbestos-free or contains no asbestos, but it is not actually on each
individual sheet.
REMARK (Mr. Singe): Well, this is what we would need.
REMARK (Mr. Jones): It is one we are certainly thinking about. Just on that
point, one of the things that we did try in the past was to slightly
pigment the sheets to differentiate them form asbestos, but unfor-
tunately we ran into a lot of problems. Some problems were attributed
to inconsistency in pigmentation that caused one batch of sheets to
be quite a bit different from another batch'. Also people who wanted
to continue using 6RC wanted the product to have the same appearance,
so it was somewhat self-defeating and we have since abandoned the
approach. But individual labeling of the sheets is probably a good
thought.
135
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REMARK (Mr. Spell): I am from Johns-Manville.
First of all I want to congratulate Cem-FIL on a good job in the
development of their Cem-FIL glass and the glass fiber reinforced
cement products and I want to congratulate Mr. Jones on the way he
discussed the fact that you cannot use the numbers that are printed.
In other words, modulas of rupture does not mean a thing. What
really counts is what strength can you count upon in the material and
the strength that you can count upon in the glass-reinforced cement
for the long run, is the strength of the matrix.
One point that he. did not mention is the fact that alkaline-resistant
glass is not alkaline-resistant. It resists alkali better than normal
glasses. So you still have a rate of reaction with the cement and
that rate of reaction is temperature-dependent. In fact, the rate
of reaction increases about twice for every 10 degrees change in
temperature. The data that were presented are data in weathering in
England, which is relatively mild. In Washington in the last few
days I think the rate of reaction would have been about three to four
times greater and the life spans that were mentioned would have been
thus reduced by that same amount. When you take a look at the 28-day
strength data you have to view that with a little bit of trepidation
as compared to asbestos cement, which increases in strength with time.
REMARK (Mr. Jones): I would just like to respond to that. The weathering data
are not just based on temperate climatic conditions in England. Ever
since the start of the project weathering sites have been established
around the world and the data have always been taken as an amalgam of
test data from all the various weathering sites.
These weathering sites are in places like Nigeria, where you have
tropical conditions, and hot desert conditions such as exist in the
Middle East. We have weathering sites throughout the United States.
We also have various freeze/thaw weathering sites. So, the data are
not just based on a temperate climate condition.
I accept the point that, yes, hot, wet conditions are worse than hot,
dry conditions, for instance. In hot, dry conditions you get very
little change in physical properties; in hot, wet conditions you do.
But in addition to the live long-term weathering program, there is
also an extensive amount of work being done on hot-wet conditions.
By hot* wet I mean hot water over 50°C and we have now an accelerated
weathering procedure that will stimulate the worst conditions, which
are tropical conditions, and a lot of the data form an amalgam of all
these different conditions. It is not just one particular condition.
QUESTION (Mr. Speil): I realize that you have weathering stations all around.
Would you give us the length of time that it takes for the strength
to decrease in, let us say, Nigeria?
136
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ANSWER (Mr. Jones): Now you are getting a little bit out of my realm. The
material always reaches a stable level. It does not continue to fall.
That is one thing I should point out. So, we are just talking about
the rate at which it reduces to reach the stable condition. The
quickest place to reach the stable level has been determined in places
like Singapore and Nigeria to be about 2 years. In conditions such as
those in England, it is about 4 to 5 years to reach the same level and
in the hot desert conditions it can take 10 to 15 years. But I should
stress that the stable level is the important level from the point of
view of the design considerations and the design velocity we have
takes into account the stable level that is reached.
I should also stress that I am talking about the original Cem-FIL
fiber on which a lot of the long-term test data is based. For the
fiber that was introduced earlier this year, much of the data are
simply based on accelerated weathering programs and, to my knowledge,
we only have about 2 years of actual data on that fiber. There you
are extending the length of time by about a factor of 5 to 10 depending
on the particular environmental conditions.
QUESTION (Mr. Speil): Four to five from your own people.
ANSWER (Mr. Jones): Well, it depends on the particular environmental
conditions.
QUESTION {Mr. Speil): However, the stable level will be the same: 2,000,
approximately?
ANSWER (Mr. Jones): For the original fiber.
QUESTION (Mr. Speil): What is the new fiber?
ANSWER (Mr. Jones): For the new fiber it is about 3,000.
ANSWER (Mr. Speil): It will be 2,000.
REMARK (Mr. Hawley): I am from Marietta Resources.
Getting back to this question of marking nonasbestos products to show
that they are asbestos-free* this is in fact being done by two, at
least, and possibly three manufacturers of calcium silicate pipe insula-
tion using suzorite mica. The mica is put in a small percentage.
It is visible because it is an amber colored flake, a rather large
flake, and this is a mark that shows that the product is asbestos-free.
To do this on sheet products you would have to do it on the back layers.
I do not know if it would be possible for you to do it with GRC, but
I think it would be possible. The advantages of this type of product
are that it is inert, it will stand up to any amount of weathering, it
does not change color, and it is highly visible for the amount of
dollars involved.
137
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REMARK (Mr. Spell): I might add that Johns-Manville is using that mica to mark
their calcium silicate insulation and we think it is a very good way
of doing it.
138
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SUBSTITUTES FOR ASBESTOS-CEMENT PIPE
by
Mr. Richard A. Simonds and Mr. James L. Warden*
U.S. Department of the Interior
Engineering and Research Center
Denver, Colorado
ABSTRACT
The Water and Power Resources Service (formerly called Bureau of Reclamation)
has installed over 9,600 miles of water conveyance pipelines, ranging in
diameter from 4 inches to 21 feet, that have incorporated many types of pipe.
Since the first asbestos-cement (A/C) pipe was placed in 1957 on a Service
project, over 1,100 miles of asbestos-cement pipe has been installed by this
agency.
A/C pipe has proved to be quite competitive — approximately 80 percent of all
pipe that is 24 inches in diameter or less, regardless of pressure class, in-
stalled on Service's projects is A/C pipe.
The Service has 13 different types of pipe that it considers for use in con-
struction specifications for water pipelines. Each of these types of pipe are
manufactured to Service specifications or have been proof tested to meet
Service requirements. The 13 different types of pipe are divided into 2 groups,
rigid and flexible. Each group has its own design parameters, pipe trench
requirements, and installation practices.
Usually each type of pipe is a composite of two or more different types of
material, such as cement, rock aggregate, steel, ductile iron, asbestos,
plastics, and fiberglass.
Each type of pipe has its own particular advantage over the other types of
pipe or it would cease to be manufactured. These advantages could be:
economics, size, pressure range, resistance to certain internal and external
environments, strength, and acceptability by the purchaser.
Topics to be discussed include: types of pipe, materials used in manufactur-
ing, design and development of each type of pipe, performance standards,
installation practices, and economic comparison.
*Presented by Mr. James L. Warden
139
-------
INTRODUCTION
The Water and Power Resources Service, formerly the Bureau of Reclamation,
was created in 1902 for the purpose of reclaiming lands and developing water
resources in the arid west.
In the period between 1902 and 1940 nearly all irrigated lands were
served by open ditches. Only a few pipelines were constructed and those were
mainly unlined steel pipes, cast-in-place concrete pipe and some wood staved
pipe.
i
In the period between 1940 and 1955 nearly all irrigation water pipe
distribution systems were low head, less than 25 feet of head (11 lb/in.2).
The pipe used was unreinforced concrete pipe with mortared joints. Most of
these systems have been replaced, but some are giving satisfactory service.
In the mid-fifties the rubber gasket pipe joint became available to all
pipe manufacturers, and this revolutionized the pipe industry. Pipe could be
laid much more rapidly and efficiently. The rubber gasket created a flexible,
watertight joint; hence, there was an increase in confidence in underground
pipe systems.
New types of pipe were being designed for higher pressures and new mater-
ials were being used to make pipe; therefore, with all the competition between
the pipe manufacturers the costs lowered so that pipe was very, very competi-
tive to the smaller capacity open irrigation canals. So competitive, in fact,
that the Service designs and builds very few open lateral distribution sys-
tems today.
The Service has 13 different types of pipe that it considers for use in
construction specifications for water pipelines. Each of these types of pipe
is manufactured to Service specifications or has been proof tested to meet
Service requirements. The 13 different types of pipe are divided into two
groups, rigid and flexible. Each group has its own design parameters, pipe
trench requirements, and installation practices.
Usually each type of pipe is a composite of two or more different types
of materials, such as cement, rock aggregate, steel, ductile iron, asbestos,
plastics, and fiberglass.
Each type of pipe has its own particular advantage over the other types
of pipe or it would cease to be manufactured. These advantages could be:
economics, size, pressure range, resistance to certain internal and external
environments, strength, and acceptability by the purchaser.
THE SERVICE'S EXPERIENCE WITH ASBESTOS-CEMENT PIPE
Over 9,600 miles of pipelines, ranging in diameter from 4 inches to
21 feet, of various types of pipe have been installed on the Service's projects,
which include some of the largest pipe distribution systems for irrigation
water in the world—Westlands Water District and the Navajo Indian Irrigation
140
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Project with 670,000 acres and 110,000 acres, respectively. Over 1,100 miles
of asbestos-cement pipe have been installed since the first asbestos-cement pipe
was installed in 1957. The Service uses an average of 50 miles of asbestos-
cement pipe per year, with a maximum of 130 miles Installed in 1973.
Asbestos-cement pipe has proved to be quite competitive—approximately
80 percent of all the pipe that is 24 inches in diameter or less, regardless
of head, that is now installed on Service's projects is asbestos-cement pipe.
The Service now has had 23 year's of experience with asbestos-cement pipe
and we use it with confidence. No asbestos-cement pipeline has ever had to be
replaced because of deterioration on a Service project.
DESCRIPTION.OF ASBESTOS-CEMENT PIPE - Figure 1
Asbestos-Cement pipe was first manufactured in the early 1900's in Italy,
and introduced to the North American Market in 1931. This pipe is a mixture
of portland cement and asbestos fibers.
In the manufacturing process, controlled amounts of these materials are
blended with water. The slurry that is formed is transferred under pressure
onto a mandrel. The mandrel is removed when the pipe is partially cured. An
intermediate curing is followed by autoelaving (steam curing for 10 hours at
180°F). In Europe and Mexico water cure is used in lieu of autoclaving. Tests
have been conducted proving that autoclaving produces a product that is chemic-
ally more stable than water curing, making the autoclaved asbestos-cement pipe
much more resistant to sulfate attack and more resistant to soft water deterio-
ration because most of the free lime in the cement has been hydrated.
Only three companies manufacture asbestos-cement pipe in this country.
Two companies make it in sizes ranging from 4 inches to 24 inches in diameter
and one company makes it in sizes ranging from 4 inches to 42 inches in diameter,
All three companies make two types of asbestos-cement pipe, pressure distribu-
tion or "Class" pipe and Transmission pipe. The "Class" pipe is made in three
classes 100, 150, 200 psi and the transmission in nine classes covering a range
of pressure from 25 feet (11 lb/in.2) to 800 feet (346 lb/in.2) of head. The
class pipe has much greater safety factors than does the transmission pipe and
is not as competitive pricewise.
SERVICE DESIGN OF ASBESTOS-CEMENT PIPE
The Service has its own pipe design standards for most of the pipe that it
uses as alternatives in its specifications. The Service designs for asbestos-
cement pipe were developed in conjunction with the asbestos-cement pipe indus-
try and the ASTM (The American Society for Testing and Materials) C-17
Committee. The Service's standards are very similar to ASTM's Standard
Specifications for Asbestos-Cement Transmission Pipe No. C668, except the
Service includes a selection table. These designs are based upon the com-
bined loading theory, developed by the late Professor W. J. Schlick of Iowa
State College. The parabola in Figure 2 represents the relationship at the
point of breaking between internal pressure and external load under three
edge bearing.
141
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TAPERED SURFACE -^
JS
N)
JOINT DETAIL
ROUND RUBBER GASKET
(BELOW COMPRESSED)
KEASBY and MATT I SON TAPERED RING
JOHNS -MANVILLE V-RING
RUBBER JOINT GASKET
Figure 1. Asbestos-cement pipe.
-------
OJ
SCHLICK FORMULA
w=
EXTERNAL CRUSHING LOAD
lb/linear ft.
Figure 2. Asbestos-cement pipe design.
-------
The equation (Schlick's formula) for this load/pressure parabola is ex-
pressed as:
w - W J
p
where P = ultimate hydrostatic pressure with no external crush load, in psi.
W = ultimate crush load with no hydrostatic pressure, in Ib/lin ft
equal to 3-edge bearing load equivalent.
p = hydrostatic pressure including safety factor, in combination with
w which will cause failure, psi.
w = crush load including safety factor, which in combination with p
will cause failure, Ib/lin ft in 3-edge bearing test.
Once the unloaded bursting pressure of the pipe and the ultimate crushing load
have been determined, combined loading theory determines the rest of the curve.
Listed as follows are the other pipe options that the Service included in
its specifications for pipeline conveyance and distribution systems:
Concrete Pressure Pipes - Figure 3
1. Reinforced Concrete (Bar pipe)
2. Reinforced Concrete Cylinder Pipe
3. Monolithic
4. Noncylinder Prestressed Concrete
5. Embedded Cylinder Prestressed Concrete
6. Lined Cylinder Prestressed Concrete
7. Pretensioned Concrete Cylinder
Steel and Iron Pipes
8. Steel pipe - Mortar lined - Various types of coatings
9. Ductile Iron
Plastic Pipes
10. Reinforced Plastic Mortar (RPM)
11. Reinforced Thermosetting Resin (RTR)
12. Poly Vinyl Chloride (PVC)
144
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Oi
TYPE OF PIPE
Reinforced Concrete
(Bar Pipe)
Reinforced Concrete
Cylinder Pipe
Non-Cylinder
Prestressed Concrete
Embedded Cylinder
Prestressed Concrete
Lined Cylinder
Prestressed Concrete
Pretensioned Concrete
Cylinder Pipe (P.T.)
STEEL
CYL.
X
X
V
X
1
X
WON-
CYL.
X
X
MILD
REINFORCING
BAR
X
X
X
HIGH
STRENGTH
WIRE
X
Wrapped on
Con_c_peteJ)ore_
X
X
DESIGN
BASIS
Rigid
Rigid
Rigid
Rigid
Rigid
"Rigid"
Flex.
Figure 3. Types of concrete pressure pipe.
-------
The above listed pipe options cannot all be used as substitutes, because
of the manufacturer's size and head class restrictions.
The following is a description of these pipe options, which includes the
design and manufacturing parameters of each type of pipe:
REINFORCED CONCRETE PRESSURE PIPE
General
Reinforced concrete pressure pipe is furnished in sizes from 12-inch diam-
eter on up. The largest the Service has installed has been 132-inch diameter
(11 feet), but industry has provided up to 216 inches (18 feet) for some power-
plant cooling lines. It can be provided in pressure classes up to 150 feet
of head (65 lb/in.2) and for burial depths up to 20 feet. As such, it is
competitive with A/C pipe only in sizes from 12 to 36 or 39 inches in diameter
and low head classes - 150 feet and less.
Joints
Reinforced concrete pressure pipe is normally supplied with integral
bell and spigot joints utilizing a rubber gasket to obtain watertightness.
A double spigot joint with a steel coupling sleeve can also be furnished. The
most common configuration which has been supplied on Service projects incor-
porates a gasket groove formed in the spigot of the pipe as shown in Figure 4.
The Service terms this configuration a "Type R-4" joint.
Manufacture
The two common methods for producing concrete pressure pipe are by ver-
tically casting or centrifugally casting processes. For vertically cast pipe,
the concrete is introduced at the top of the form, and vibrators attached to
the outside of the forms insure solid dense concrete. In the centrifugally
cast process, the forms are spun fast enough to hold the concrete in place by
centrifugal force. "Knockers" hitting against the outside of the spinning
form provide vibration. Free water in the concrete mix is forced to the .
inside surface by the centrifugal action where it is blown out one end of the
form. As a result, the water-cement ratio of the final concrete mix is quite
low, and the initial set time is shortened.
Most concrete pipe producers attempt to get a 1-day turn-around with their
forms. To accomplish this, an overnight cure using steam or high temperature
moist heat is provided. After the forms are stripped, the curing is continued
until the concrete has gained sufficient strength for handling.
Wall thickness of reinforced concrete pipe are generally approximately
1/12 of the diameter of the pipe for the larger sizes and vary down to a
2-inch minimum thickness for the smaller sizes.
Reinforcement is ordinary concrete reinforcing steel usually formed into
circular cages. Only one cage is used in 24-inch pipe and smaller, either
one or two cages (providing an inner and outer layer of reinforcement) can be
146
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Steel Reinforcing Cages
JS
"SJ
Rubber Gasket
'''''-'
^^ • • • . • • ^* • * * * . • • • * • • • • •
• . • • . . • . -0. •.••..'. 'Q .'.•-.. .0.
•"•'•».•."• • •••-.* . • .' • • . • .
•'•';•'••'•':'•'••• '••'•"- "^
•V /ta •-.•fa-.-9; .;®.-A-.ej-.-.t2|. :..^..-
• • . • • . . "*^ • . . • . « . • . . •*•< . . ."
Figure 4. Reinforced concrete pressure pipe (bar pipe).
-------
used in 27- to 36-inch sizes, and two cages are used in pipe larger than
36-inch diameter.
As an alternative to two layers of reinforcement, one cage formed in an
ellipse can be used in pipe from 18 to 72 inches in diameter. With the ellip-
tical shape, the reinforcement can be located within the pipe wall so that it
is at the inside face at the top and bottom of the pipe and at the outside face
at the sides of the pipe in order to accommodate the tensile stresses result-
ing from the bending moments which occur at these locations when the pipe is
loaded. Use of elliptical reinforcement requires the cage to be accurately
oriented in the forms at the time of manufacture and the location of the field
top be permanently marked on the pipe unit. At the time of installation, the
contractor must then install the pipe so that the field top of the pipe unit
is on the vertical center line of the pipe, with a maximum allowable deviation
of 10 degrees from the vertical. Elliptically reinforced pipe just does not
work very well if it is laid on its side.
Design
*•
Reinforced concrete pressure pipe is designed as a rigid structural ring
which transmits the applied loadings down through the pipe wall into the
foundation soil. As such, the pipe is weakest when subjected to a line load-
ing on top and a line reaction on the bottom and is strongest when subjected
to a uniform radial loading all around the pipe, such as an external pressure.
The installed pipe is subjected to a combination of loadings instead of the
idealized loadings just described. The soil above the pipe applies varying
loads to the pipe which are assumed to act radially over the top and sides of
the pipe, the dead load of the pipe itself are vertical forces acting down-
ward, the weight of the water inside the pipeline applies forces acting radially
outward; and' hydrostatic pressure inside the pipe results in uniform radial
forces acting outward: The reaction force from the supporting foundation soil
depends entirely on the construction procedures used at the time of installa-
tion. As stated previously, a line reaction is a severe loading condition,
and the pipe is much stronger if the reaction can be spread out over a par-
ticular area at the bottom of the pipe. The angle at the bottom of the pipe
over which the loads are transmitted from the pipe wall down into the founda-
tion soil is termed the "bedding angle," with a zero degree angle representing
a line reaction. As an economical compromise, the pipe for Service projects
is designed for a bedding angle of 90 degrees. To ensure that this angle is
obtained, our specifications require select material to be placed under the
haunches of the pipe and up to a height of three-eights of the pipe O.D.
This material must be compacted to 95 percent of standard Proctor density
in order to provide the necessary support for the pipe.
Analytical studies have been performed to derive the mathematical coeffi-
cients by which the internal moments, thrusts, and shears in the concrete pipe
wall can be obtained for the various loading conditions. Once these are known,
ultimate strength reinforced concrete theory is used to obtain the required
wall thickness and amount of reinforcement.
148
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PRETENSIONED CONCRETE CYLINDER PIPE (PT)
General
Pretensioned concrete cylinder pipe is furnished in 10-inch through 54-inch
diameters, pressure classes up to 700 feet of head (300 lb/in.2), and for burial
depths up to 20 feet. It is very competitive with A/C pipe in sizes larger
than 24 inches and in the higher pressure classes.
Joints
PT pipe utilizes what the Service terms an "R-2" type of joint. This
joint incorporates a rubber gasket contained in a formed groove in a steel
spigot ring. See Figure 5. The rolled steel shape from which the spigot ring
is formed is termed a "Carnegie" shape. The steel bell ring is a rolled flat
plate properly sized to mate with the spigot ring. Tolerances in this type
of joint are extremely close with the difference in the circumferences of
the outside of the spigot ring and the inside of the bell ring being less
than 3/16 inch. Nevertheless, with the smooth steel surfaces in the joint,
there is little or no tendency for the gasket to fishmouth, and there are
very few construction problems associated with this type of pipe.
Manufacture
Forming the steel cylinder is the first step in the manufacture of PT
pipe. This is normally done by rolling a continuous sheet of flat steel plate
into a helix and automatically butt welding the edges together. The resulting
helically welded cylinder is then cut to the proper length, and the spigot and
bell rings are welded on. At this stage, each cylinder is hydrostatically
tested at a pressure which stresses the steel to 20,000 lb/in.2. At this pres-
sure any defects in the welds are readily apparent and are repaired by manual
welding. After hydrostatic testing, the mortar lining is applied to the in-
side of the cylinder by centrifugally spinning and either steam or water cured
to obtain its design strength. Steel reinforcing rod is then wound around
the cylinder under a prestressing tension of 8,000 to 10,000 lb/in.2, and the
pipe unit is completed by the application of a mortar coating on the outside
of the reinforcing rod.
Design
For design purposes, PT pipe is divided into two categories. Eighteen-inch
diameter and smaller pipe is considered to be rigid, and the mathematical
coefficients for the moments, thrusts, and shears are used based on a 90-degree
bedding angle as for reinforced concrete pipe. Pipe larger than 18 inches is
considered flexible and moments and thrusts are determined using beams on
elastic foundation theory and considering the pipe to be supported for the
full 180 degrees on the bottom. After moments and thrusts are determined,
the design proceeds according to ultimate strength theory for reinforced
concrete. The steel material for the cylinder and the reinforcing rod wrap
is specified so that the cylinder will have a lower yield strength than the
rod wrap, and because of the effect of the initial prestressing force, failure
of the pipe will occur with the cylinder and rod wrap at their respective
yield strengths and the mortar lining at its ultimate compressive strength.
149
-------
in
O
Rod Reinforcement
Grout Placed After
Instal lation
Steel Cylinder-1 Steel Spigot Ring J
Rubber Gasket
Steel Bell Ring
/-Cement-Mortar Coating
L
Cement-Mortar or
Concrete Lining
Cement-Mortar Placed
in Field
Figure 5. Pretensioned concrete cylinder pipe.
-------
To provide the full 180-degree bedding consistent with the beams on elas-
tic foundation assumption, the soil backfill under the haunches of the pipe
and at the sides of the pipe up to a depth of 0.7 times the pipe outside diam-
eter is specified to be compacted to 95 percent of Proctor density.
DUCTILE-IRON PIPE
General
Ductile-iron pipe is furnished in diameters from 3 inches through 54 inches
and for pressure classes up to 1,000 feet of head (450 lb/in.2) including
transient surge pressures. When installed in a very good trench laying
condition, the pipe can withstand burial loads exerted by from 55 to over
100 feet of earth cover, depending on size. Although somewhat more expensive
than A/C pipe, some economics can be achieved with ductile-iron pipe by
relaxing some of the trench installation requirements.
Being a metal product, due tile-iron pipe is subject to electrolytic corro-
sion when installed in areas where soil resistivity values are low. In these
areas, cathodic protection must be provided which would entail electrically
bonding the pipe units together by welding a jumper across each joint. In
many instances, providing test stations to monitor the pipeline may be suffi-
cient, but in severe, situations an impressed electrical current may be required.
Additional corrosion protection is provided by normally installing the pipe
with a polyethylene wrap on the outside of the pipe.
Joints
For irrigation and long water supply pipelines, ductile-iron pipe is
normally furnished with bell and spigot, rubber gasketed, push-on type joints.
Mechanical type rubber gasketed joints and standard flanged joints can also be
provided for other applications. In the bell and spigot joint, the gasket
is contained in an annular space in the bell and has a special cross sectional
shape in order to seal effectively agaMnst the smooth spigot end of the pipe.
Manufacture
Cast iron and ductile iron are essentially alloys of iron containing car-
bon and other chemicals. The primary difference between cast and ductile iron
is that in cast iron, the carbon occurs as free carbon or graphite in the form
of flakes interspersed throughout the metal. In ductile iron, the carbon is
in nodular or spheroidal form and more finely interspersed in the metal. This
change in the graphite form is accomplished by adding, at the appropriate
moment, a charge of magnesium to the molten iron. The pipe is then centrifu-
gally cast in a spinning mold. When the molten iron has solidified but is
still red hot, it is removed from the mold and anneal led for an appropriate
period of time. When cool, a thin cement mortar lining is applied to the in-
side of the pipe.
Design
Since ductile iron is a homogenous material, the design of this type of
pipe is relatively straightforward and is based on a minimum yield strength in
151
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tension of 42,000 lb/in.2. Ductile iron is considered a flexible pipe although
in the smaller sizes it has significant ring stiffness which is reflected in
the design equations. The equations also consider the lateral support that
a flexible pipe receives from the compacted backfill soil at the sides of
the pipe when the pipe is deflected under external earth and live loads.
Based on the bending stresses due to external loads and tensile stresses due
to internal pressure, standard tables have been prepared from which the
required minimum wall thickness can be determined for a particular installation.
In the determination of the required wall thickness, a design safety factor of
two is applied to the tensile yield stress and a design ring bending stress
of 48,000 lb/in.2 is used which is considered conservative and appropriate.
The bending stresses are determined considering a maximum design deflection
of 3 percent of the pipe diameter.
REINFORCED PLASTIC MORTAR PIPE (RPM)
REINFORCED THERMOSETTING RESIN PIPE (RTR)
General
These two types of plastic pipe are composed of fiberglass and polyester
plastic resin. In addition, RPM pipe also contains ordinary sand as an inert
filler to build up the pipe wall. RTR pipe, also frequently call FRP for
fiberglass reinforced plastic, contains only glass and resin. Other types of
resins, such as epoxy and vinyl ester, are also used for these types of pipe,
but due to their expense, they are seldom utilized for irrigation or water sup-
ply pipelines. RPM pipe is furnished in sizes from 8 inches to 54 inches in
diameter while RTR pipe can be obtained as small as 1-inch diameter. Although
the Service limits the maximum size for these types of pipe to 54 inches,
industry has the capability of manufacturing these products up to 144 inches
(12 feet) in diameter. Both types can be provided for pressure classes up to
500 feet of head (220 lb/in.2) and for burial depths up to 20 feet. As with
PT pipe, these products would be competitive with A/C pipe in sizes larger
than 24 inches and in the higher pressure classes.
Joints
To date, RPM pipe has only been made with an R-4 type joint, that is,
with the rubber gasket confined in a groove in the spigot. RTR pipe also is
manufactured with R-4 joints but, in addition, can be made with the gasket
groove in the bell and can also utilize a separate coupling such as A/C pipe.
Figure 6 shows examples of RPM and RTR pipe joints. With smooth plastic
surfaces, these joints have little tendency to have fishmouth gaskets; how-
ever, liberal use of lubricant during installation is still highly desirable.
Manufacture
Both types of pipe can be manufactured by either a filament winding pro-
cess or by centrifugally casting. When centrifugally cast, the fiberglass and
resin (and sand, in the case of RPM) are introduced into a mold which is spun
until the catalyzed resin hardens. The fiberglass can either be woven glass
cloth put into the mold while at rest or it can be introduced as short chopped
fiber strands about 4 inches long while the mold is spinning. In the filament
152
-------
Y(Min.)'OJOd (Average)
GASKET GROOVE ON SPIGOT iUO OF PIPE
/>i
r*~,
rt
3
3
;» o. S04 (A
(b) GASKET GROOVE IN BELL
NOTES A Ua*/mum»20*
An ou*si
-------
winding process, ^continuous fiberglass strands are bundled together, passed
through a bath of catalyzed resin, and wound on rotating mandrel which moves
longitudinally past the winding station.
For RPM pipe, the fiberglass is wound on the mandrel almost perpendicular
to the mandrel, and additional layers of fiberglass, with the strands oriented
longitudinally, are applied to give the necessary longitudinal beam strength.
Sand is added periodically in the process, additional glass is wound on top
of the sand, and a final sand coat is applied to the exterior surface.
For RTR pipe, the fiberglass is wound on the rotating mandrel at an angle
of from approximately 57 to approximately 75 degrees with the longitudinal axis
of the pipe. This gives the pipe its required beam strength instead of
providing longitudinally oriented glass fibers. The actual angle is dependent
upon the relative values of the required beam strength and hoop strength.
After winding, both RPM and RTR pipe units are allowed to cure in an oven
environment until the resin has completely hardened, after which the pipe
unit is removed from the mandrel. With RPM pipe, the spigot is then cast into
the prepared end of the pipe by placing the pipe on end in a heated mold into
which resin is poured. No fiberglass is included in this operation.
Design
In these types of pipe, all stresses in the pipe wall are considered to be
carried by the fiberglass only and that the resin only provides water tightness
and that holds the fiberglass in place. A characteristic of plastic pipes such
as these is that when subjected to a fairly high stress level which is held
constant, the pipe will fail after a particular period of time. If subjected
to a lower stress level, it will take a longer period of time for the pipe to
fail. This strength regression relationship between stress level and time to
failure plots as a straight line on a log-log graph, that is, when log time is
plotted versus log stress, and the mathematical relationship can be determined
through a statistical analysis of data from a long term laboratory testing
program. From this relationship, a design stress level can be established
which will result in an estimated time to failure which is sufficiently long
so as to ensure that the pipe will not fail for the life of the project.
(For a typical RPM compound, if the design stress is taken as one-half of the
stress level which will cause failure in 100,000 hours (11.4 years), the
estimated time to failure for the design stress level is approximately 28,000
years.) The required area of fiberglass is then established for a particular
installation so that this design stress level is not exceeded.
Both RPM and RTR pipe are considered flexible pipes and, as such, require
well compacted backfill underneath and at the sides of the pipe to prevent
excessive deflection. This backfill should be compacted to 95 percent of Proc-
tor density to a depth of 0.7 times the outside diameter of the pipe.
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POLYVINYL CHLORIDE PIPE (PVC)
General
PVC pipe ±s furnished in sizes up to 18 inches in diameter and as small as
1/8-inch diameter tubing. Some manufacturers are in the process of expanding
the range up to 22- or 24-inch diameter, and by this time, some of these larger
sizes may be available. PVC irrigation pipe has pressure ratings based on
the ratio of the dimensions of the outside diameter of the pipe to its wall
thickness so that pipe with the same dimension ratio will have the same pressure
carrying capability, regardless of size. Other types of PVC pipe, such as
schedule 40, 80, and 120 pipe, having the same dimensions as the corresponding
iron pipe, are also available. The pressure ratings of the schedule pipe vary
with the pipe diameter, with the smaller pipe being considerably stronger than
the larger pipe. With the standard dimension ratios, irrigation pipe can be
obtained with pressure ratings up to 700 feet of head (300 lb/in. ) and for
burial depths well over 20 feet.
Joints
PVC irrigation pipe is furnished with either rubber gasketed joints or
solvent cemented joints. Because of the reliability and ease of installation
of the rubber gasketed joints and because successful solvent welding is highly
dependent upon temperature, humidity, blowing dust, and highly qualified work-
men, the Service requires rubber gasketed joints for PVC line pipe. The rub-
ber gasketed joints are either of the separate coupling type, similar to A/C
pipe, or else are bell and spigot with an annular space for the gasket formed
in the bell.
Manufacture
Polyvinyl chloride is a thermoplastic resin. That is, it can be repeatedly
softened by an increase in temperature and hardened by a decrease in tempera-
ture. In the highly automated manufacturing process, the raw resin, in powder
form, is fed to an extrusion machine where it is heated under pressure (2,000
to 5,000 lb/in.2) until the resin particles fuze together into a viscous,
plastic mass. The material is extruded through a forming die which molds it
into a cylindrical shape and then immediately cooled into a solid state by
chilled water. Since the operation is continuous, the pipe is automatically
cut to length by a moving saw that travels at the same speed as the pipe is
being extruded. For bell and spigot type pipe, the bell is then formed by re-
heating one end of the pipe to a pliable state, forcing it over a forming
mandrel, and again cooling it to a solid state.
Design
Thermoplastic compounds, such as PVC, exhibit the same strength regression
characteristics as the fiberglass reinforced compounds as described under RPM
and RTR pipe. Therefore, the design stress level for PVC pipe is also based on
the long term strenth of the product as determined by a laboratory testing
program. The required wall thickness can then be established so that the
design stress is not exceeded.
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PVC pipe is also a flexible pipe' and will deflect tinder external trench
loadings. Many of the pipe manufacturers recommend compacted backfill at the
sides and up to 1 foot above the top of the pipe, and we require highly com-
pacted material to 6 inches above the pipe. In smaller diameters and with
greater wall thickness, however, the pipe does have significant ring stiffness,
and the pipe can be designed to carry significant trench loads with little
lateral support from the soil at the sides of the pipe. This allows relaxa-
tion of the compaction requirements for the backfill soil, resulting in a sav-
ings in installation cost.
STEEL PIPE
General
Steel pipe is practically unlimited in size and pressure ratings. The
largest steel pipe the Service has installed for water supply purposes is
96 inches in diameter; however, 40-foot-diameter penstocks for dams and
power plants can be considered as steel pipe. The service requires steel
line pipe to be cement mortar lined on the inside and coated on the outside
with either cement mortar or coal tar enamel wrapped with kraft paper. Steel
pipe- is considerably more expensive than A/C pipe but can be used as a very
acceptable substitute.
Joints
Joints in steel pipe are either welded or are bell and spigot type with a
gasket groove rolled either in the bell of the pipe or on the spigot end.
Figure 7 shows a typical joint with a gasket groove rolled in the spigot.
Some manufacturers can furnish a joint incorporating a carnegie shaped spigot
ring welded to the steel cylinder. This joint has a big advantage due to the
stiffness of the ring; however, it is more expensive and seldom done. Welded
joints are normally butt or lap welded after which the mortar lining and
appropriate coating are placed in the field.
Manufacture
Steel pipe is manufactured either by helically welding a continuous roll
of steel sheet or by forming the cylinder from flat plate and using longitudinal
welds. If rubber gasketed joints are being provided, the bell and spigot are
rolled to their appropriate shape, and the cylinder is hydrostatically tested.
Many of the designs for steel pipe require very little wall thickness,
and the cylinder has a tendency to warp due to the heat of welding. To elim-
inate this, the hydrostatic pressure inside the cylinder is raised to stress
the steel slightly beyond its yield point. This causes the cylinder to round
out, and, because the steel has yielded slightly, to retain its circularity
when the pressure is reduced. The slight increase in diameter resulting from
this operation is taken into account when forming the cylinder initially.
After the cylinder is rounded out, the mortar lining is centrifugally
spun on the inside of the pipe and the appropriate coating applied to the
outside.
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Grout Placed
After Installation
Steel Cylinder
Ui
Cement
Mortar Lining
Cement Mortar Coating
Wire Mesh
Reinforcement
r' '•'•'•'
_
Cement Mortar Placed
After Installation
Rubber Gasket
Figure 7. Steel pipe (mortar lined and coated)
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Design
Steel pipe is designed as a flexible conduit, but its ring strength and
arch strength are also considered. The design procedure follows that in AWWA
Manual Mil which covers three design cases:
1. When the wall thickness and diameter selected to meet pressure
requirements are such that its ring strength is sufficient
to carry all external trench loads without deflections greater
than 2 percent of the pipe diameter.
2. When the ring strength is sufficient to carry part of the ex-
ternal trench loads, but not all of it without undue deflection.
Some side support must be provided by the backfill soil under
and at the sides of the pipe.
3. When the ring strength of the pipe is so low that it can carry
very little, if any of the external trench loads without undue
deflection. Full mobilization of the passive resistance of the
soil at the sides of the pipe is required.
Charts and tables are provided in the manual to determine the allowable
earth and live loads that can be carried by a pipe of a particular diameter
and wall thickness.
Steel pipe on the majority of Service projects would fall into the third
design category as described above. In order to ensure the necessary side
support for the pipe, we require the backfill soil to be compacted to 95 per-
cent of Proctor density up to a depth of 0.7 times the outside diameter of
the pipe.
ADDITIONAL TYPES OF PIPE SUBSTITUTES
The substitute pipes as described in the preceeding portion of the paper
are those pipes that have been thoroughly investigated and have been accepted
by the Service for use in its specifications. It is not the intent of this
paper to represent that these are the only types of pipe available or the
only ones that can be used.
Listed as follows are some of the other types of pipes that are presently
being manufactured that could possibly be substituted safely and economically
for asbestos-cement pipe:
1. Concrete pressure pipe reinforced with steel wires (fibers)
2. Concrete pressure pipe reinforced with fiber glass
3. Polyethylene (PE)
4. Polybutylene (PB)
5. Acrylonitrile Butadiene Styrene (ABS)
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It usually takes approximately 5 years of investigations and testing
before the Service will use a new type of pipe as an option in its specifica-
tions. The purpose of this conservatism is that the Service must be reasonably
sure that the pipe will last at least the length of the repayment contract with
the water districts, which is usually 50 years.
AGGRESSIVE TRANSPORTED WATERS
Aggressiveness of water transported through Asbestos-Cement Pipe as described
by ASTM C500 Standards is as follows:
Highly aggressive pH + log (AH) < 10
Moderately aggressive pH + log (AH) = 10.0 to 11.9
Nonaggressive pH + log (AH) _> 12.0
where
pH •» index of acidity (or alkalinity) of the water, standard pH units
A - total alkalinity, ppm as CaC03, and
H = calcium hardness, ppm as CaCOa
If the pH + log (AH) is < 10, the water is highly aggressive and some means
must be taken to Insure the integrity of asbestos-cement pipe. This also
applies to all types of cement mortar lined pipe. Lining of the inside of the
pipe with an inert material is one solution. Ductile-iron pipe uses an as-
phaltic seal coat over its cement mortar lining for protection. Treatment
of the water before entering the pipeline is another solution.
ECONOMICAL ADVANTAGES
Asbestos-cement has an economical edge over the other types of pipes, for
sizes 6 inches to 24 inches in diameter for the following reasons:
1. It costs less to produce because the method of manufacturing
asbestos cement pipe lends itself to automation and the
materials used in making the A/C pipe cost less in these
diameters.
2. Asbestos-cement is a rigid type of pipe. It takes less work
in installation than does the flexible type pipe because al-
most half as much compaction is required. Cathodic pro-
tection is not needed for asbestos-cement pipe.
3. Cathodic monitoring stations are required for all steel,
ductile iron, and steel cylinder pipe, which require all
joints to be bonded.
4. If the soil resistivity is low, less than 2,000 ohm centi-
meters, cathodic protection must be included in the cost of
steel and steel cylinder and ductile iron pipes.
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For diameters greater than 24 inches and heads higher than 200 feet, the
other listed substitute pipes compare very favorably or are more economical
than asbestos-cement pipe.
SUMMARY
1. The Service has installed an 1,100 miles of asbestos-cement
pipe during the past 23 years and none has had to be replaced
because of deterioration.
2. Reinforced Concrete, Fretensioned Concrete, Lined Cylinder,
Steel, Ductile Iron, Reinforced Plastic Mortar, Reinforced
Thermosetting Resin, and Poly Vinyl Chloride pipes can all
be competently substituted for asbestos-cement pipe, but are
not economical substitutions for pipe diameters of 24 inches
and less.
3. New types of pipes are being manufactured that could be sub-
stituted for asbestos-cement pipe, but usually it takes about
5 years to investigate and test them before they are accepted
by the Service.
4. Asbestos-Cement Pipe and all cement mortar lined pipe should
be coated on the inside of pipe with an inert material if
waters having an aggressive index of less than 10 are trans-
ported through them.
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DISCUSSION ON SUBSTITUTES FOR ASBESTOS-CEMENT PIPE
QUESTION (Mr. Levy): You said that you have never had to replace any AC
pipe in 23 years of experience. Can you make similar claims for
the other materials that you specified and now use?
ANSWER (Mr. Warden): Yes. We have had to replace some reinforced bar pipe
where we have had some expansive soils. This was probably our
fault because we may have under-designed it. We have had to re-
place our reinforced concrete pipe and also steel pipe that had
rusted out because it did not have cathodic protection. Now we
are including cathodic protection on all of our steel and steel
cylinder pipes.
REMARK (Mr. Atkinson): I am Deputy Executive Director of the American Water-
works Association.
I would like to file with the Chairman of the working group a
paper that was developed by our California/Nevada section with
regard to asbestos-cement pipe.
I would also like to say that our association has standards for
practically all the pipe that is manufactured in this country,
particularly pipe that is used in drinking water.
The Association takes a neutral part on what type is to be used
and thinks that should be left up to the user based on the recom-
mendations that he receives from his engineering consultant for
the particular project for which the pipe is to be used. We do
feel, however, that regulations that might be issued by the
Federal government should be based on sound scientific knowledge
and not mere conjecture that some particular product or process
may have an adverse effect on the health of persons.
I think this is very important because one of the reasons for
this workshop, I think, is for EPA and the Consumer Product
Safety Commission to try to gather additional information on
whether or not they are going to apply certain rules and regula-
tions with regard to the use of asbestos.
QUESTION (Dr. Millette): In the Service you apparently make measurements
of the soil resistivity or corrosion problems of the exterior
of the pipe. Do you also make measurements of the water quality
in terms of corrosion index or other indexes and do those come
into your specifications at all?
ANSWER (Mr. Warden): We actually do make measurements of the different
types of water and the conditions that the pipe is going to be
laid in. In fact, in the West we have a very high sulfate con-
tent where we lay our pipe and in our concrete structures we
require Type 5 cement and we do take readings to determine what
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QUESTION
ANSWER
type of soil our pipelines are going to be put into. We have
a standard for almost every type of pipe but we also have
construction specifications and in these construction specifi-
cations we will spell out what type of soils the contractor
will encounter.
(Dr. Millette): What about the type of water that he would
encounter; is that included?
(Mr. Warden): Yes.
QUESTION (Dr. Millette): There are some water utilities in the Northeast
that require an inner coating on asbestos-cement pipe to possibly
prevent corrosion problems. Have you ever specified or used
coating?
ANSWER (Mr. Warden): We have never used linings in the AC pipe. We only
had one case that I know of and that was in California where the
water had an aggressive index of less than 10. So we actually
did not put AC pipe in because we felt that the water was too
aggressive for that type of pipe. We did use a double cement
lined ductile iron pipe with an asphaltic seal coat but we have
never used any linings and I do think that linings are something
that the AC Pipe Association is going to have to address.
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PANEL ON DEVELOPMENT OF SUBSTITUTES
Chairman: Richard J. Guimond
U.S. Environmental Protection Agency
Washington, D.C.
Panelists: Mr. Robert Moore
Elson T. Killam Associates
27 Bleeker Street
Milburn, N.J. 07041
Mr. John Gurtowski
Materials and Processing Division
Naval Air Systems Command
Washington, D.C. 20361
Mr. Roy Steinfurth
Insulators Health Hazard Program
Asbestos Workers International
Asbestos Workers Union
1300 Connecticut Avenue, NW
Washington, D.C. 20036
Mr. James F. Reis
Director, Asbestos Policy
Johns-Mansville Corporation
P.O. Box 5108
Denver, CO 80217
Mr. Barry Castleman, Esquire
Environmental Consultant
Box 230A, Valley Road
Rnoxville, MD 21758
CHAIRMAN RICHARD J. GUIMOND
The topic for the panel is the Development of Substitutes. The purpose
of the panel is to discuss the development of substitutes from a variety of
perspectives. We have people from various organizations and vastly different
interests to consider the development of substitutes, the technical problems,
the economics, the health risk aspects, from the concerns of their individual
responsibilities.
MR. ROBERT MOORE
The American Society for Testing and Materials is a volunteer, non-
profit organization devoted to the development of product standards and test
methods. Standard and test methods for asbestos-cement products are under the
jurisdiction of Committee C-17, one of the Society's 135 technical committees.
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Committee C-17, at present, consists of 59 members. Seventeen members
are classified as producers; these members have 9 votes, the rest being non-
voting members. Ten members are classified as consumers or users, seventeen
as general interest members, and five are affiliate members.
Membership in Committee C-17 includes representatives of producers of
asbestos-cement products from firms in the United States, Mexico and Belgium.
Membership also includes producers of asbestos fibers, producers of cement,
representatives of U.S. government agencies, representatives of State and
municipal agencies, consulting engineers, and contractors. The voting
strength of the various interests is such that producers of asbestos-cement
products have about one-fifth of the total votes on the Committee.
Committee C-17 was founded in 1947 when the need for standards for
asbestos-cement products was perceived to be urgent. The first Chairman of
the Committee was Douglas Parsons of the U.S. Bureau of Standards.
The Committee meets twice a year in January and June. Task groups
studying particular problems often meet between the main Committee meetings.
Although business is transacted and problems discussed at the meetings of
the Committee, all questions relating to technical standards are decided by
letter ballot. The ASTM develops standards by the consensus method. This
means that basically all interests must agree before an action becomes final.
In addition, the Committee must follow strictly the detailed regulations of
the ASTM which requires that interests must be balanced among producers, users
and general interests, that a satisfactory percentage of ballots must be
returned, and that any ballots which contain negative notes must be discussed
and appropriate action agreed-upon.
Committee C-17 includes several sub-committees:
Sub-Committee C-17.01 - Editorial and International
This sub-committee is responsible for editorial content of standards and
test methods. In addition, this sub-committee has the function of acting as
the U.S. TAG (Technical Advisory Group) to the Technical Committee 77 of the
International Standards Organization (TC 77 covers international standards for
asbestos fibers and asbestos-cement products).
Sub-Committee C-17.02 - Research
This sub-committee helps to coordinate and collect new information with
regard to asbestos-cement products and their uses. The Research Committee
also monitors round robin product tests.
Sub-Committee C-17.03
This sub-committee is in charge of developing standards for asbestos-
cement building products, including flat and corrugated sheets, insulated
sandwich panels and asbestos-cement shingles. A major current use for
asbestos-cement sheets is packing for cooling towers.
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Sub-Committee C-17.04
This sub-committee develops standards for asbestos-cement pipe including
pipe for sewers, water mains, drainage and under drains.
Current activities in Committee C-17 include development of a recommended
standard for installation of asbestos-cement sewer pipe. In addition to
information with regard to proper installation of the pipe to provide satis-
factory structural and hydraulic performance, the standard will include
information as to proper methods for cutting and drilling operations in order
to avoid eventually dangerous occupational exposure.
The Sub-Committee on Research has been receiving updated information on
the Water and Power Resources Services tesing of autoclaved and normal cured
asbestos-cement pipe in sulfate soils and information on a test program to
develop further information on structural strength of buried piping conducted
by Utah State University.
The standards developed by the Committee include a list of definitions
peculiar to asbestos-cement products and a number of standardized test methods
such as tests for crushing strength of pipes, in addition to product standards.
Product standards include dimensional requirements, tests of strength,
and certain chemical tests. The requirements for flexural strength, crushing
strength, bursting strength, and joint tightness are based upon a combination
of requirements for construction use and consideration of manufacturers'
standards.
Because of developing concern over the possible effects of asbestos
fibers, together with the possibility that new products having properties
similar to asbestos cement products may be developed, the Committee is
currently considering changing its scope from "products deriving their essen-
tial properties from a mixture of asbestos and fibers and cement" to "fiber
reinforced cement products."
The concensus method of developing standards provides a forum where a
broad range of interests can meet and develop standards which are suitable
to all segments of the population. The procedure of letter balloting means
that those who are not able to attend the meetings can share equally in the
work of the Committee. It furthermore means that any additional information
required to come to a position on a given question can be obtained and a
ballot can be voted in the absence of group pressures.
The standards are not static; they are undergoing a continuous process
of change as new information becomes available or the need for new products
becomes evident. One example of this is the standard for transmission pipe.
This standard permits an engineered design of transmission piping using pipe
particularly tailored to the hydraulic requirements rather than the used
standard classes of pressure piping. In cases where pressures are accurately
known or controlled, transmission pipe permits a more economical use of
material.
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The committee welcomes wide participation in its work by interested
persons. The basic requirements for membership include membership in the
ASTM and a knowledge of the field.
MR. JOHN GURTOWSKI
Pressured by reports of health problems attributed to asbestos, restric-
tions on the volume of asbestos-contaminated air to which personnel may be
exposed, worker unrest, the high cost of making work areas safe and an executive
order to find an alternate material for Chrysotile AAA fiber (available only
from Rhodesia), the Naval Air Systems Command embarked upon a program
directed toward identifying substitute/alternate materials and in replacing
asbestos components with them as soon as their potential for each specific
application can be verified.
At the present time the Naval Air Systems Command has forty (40) different
types of aircraft in its inventory and the task of identifying each asbestos-
containing component in each type of aircraft and in its weapons and in
finding satisfactory alternate materials for all of them will be a long term
costly effort.
To expedite the investigation the Naval Air Systems Command has confined
its first efforts to the newest aircraft in its inventory which include the
F-18, F-14, AV-8A, and CH-53E models. Here action is being taken to identify
acceptable alternate materials as promptly as possible and make them available
as replacements when a shortage of the asbestos components is revealed either
by operating personnel or by the parts manufacturer. Admittedly, this is
somewhat of a "piece-meal" approach to solving a major problem, but it will,
hopefully, permit the Fleet to keep its aircraft flying while the search for
alternate materials continues.
To date, we have located and identified a large number of aircraft
components which contain asbestos in various amounts, none of which have been
found to release fibers in any significant concentrations during flight
operations. Regardless of this non-hazard situation, knowing that the
components may not be available in the future, they have been listed for
replacement with parts containing no asbestos.
One major concern requiring costly evaluation is the replacement of
asbestos-containing brake linings in aircraft. Here we are attempting to
substitute carbon linings, however, FAA regulations require a very costly,
long-term qualification test prior to acceptance. Currently, neither funds
nor aircraft are available to complete such a test. By using brake linings
containing asbestos, we have replaced very toxic beryllium brakes; however,
if we cannot find a satisfactory substitute for the asbestos fiber, we may
have to go back to the more acutely toxic beryllium brakes on certain high
performance aircraft.
However, the most serious related problem facing the Naval Air Systems
Command involves finding alternate materials to replace the asbestos
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containing thermal insulating liners in missiles and rockets. Little progress
in this area has been made.
Preliminary funding requirements to conduct an intensive program to
find acceptable thermal insulating liner materials may exceed $1 million.
At the present time, that type of funds is not available to us. In our
search for alternate materials, the Naval Air Systems Command is evaluating
a variety of materials for specific applications: steel wool, quartz fibers,
ceramic fibers, graphite, E-glass, S-glass, Refrasil, polyamide fibers,
ground cork, clay, and nylon fibers. From the results to date it is apparent
that some asbestos containing components, because of their critical appli-
cation in aircraft and missiles may never be replaced.
One of our major concerns to-date is the great fear of asbestos created
by widespread publicity regarding its potential carcinogenic nature. Let
me cite two examples:
The leading edges of helicopter blades are normally protected from sand
and/or rain erosion by strips of titanium or stainless steel. The adhesive
used to bond the strips to the blade contained 1 percent asbestos which, after
cure, was never touched. Operators insisted on hazard pay in using this
material. In a similar situation, an adhesive containing 6 percent asbestos,
aluminum powder and another filler, was used to detect cracks in the spars
of helicopter blades. The material was used in both manufacturing and in
repairing operations. Shutdown of both operations was threatened by fear of
asbestos exposure. Fortunately, we were able to find adhesives for these
operations which did not contain asbestos fillers, and work was permitted to
continue.
In conclusion, we, in the Naval Air Systems Command, hope that no
sweeping directive will be forthcoming in the near future banning the use of
asbestos or setting, exposure limits at such a low level as to make compliance
impossible to achieve.
Even so, the Naval Air Systems Command will continue its active program
to find alternate materials as rapidly as possible and will continue to find
reasonable efforts to solve at least a major portion of the asbestos problems.
In the long run, it is our objective to replace as many of the asbestos
containing components in our aircraft and weapons as possible with so called
"safe materials".
MR. ROY STEINFURTH
While the use of asbestos has been extremely curtailed in the insulation
industry and consequently exposure by our members to asbestos has been
drastically reduced, we are now, however,, experiencing an increase in
exposure due to renovation work, maintenance, asbestos removal and
demolition.
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We regretfully wish to inform'you, however, that in asbestos removal
and demolition we can expect a great upsurge in asbestos-related disease in
workers not associated with our organization. This is due to unscrupulous
companies, industries and contractors using non-skilled, low-paid employees
for asbestos removal, and also using unregulated dumping sites. Also many
removal and demolition sites are in crowded urban areas compounding the
risk of contamination to innocent people.
Substitute Materials
Statistics show that between 2/3 and 374 of asbestos products manu-
factured in this country are being used in construction. However in most
of these products, the asbestos is locked or sealed in, and safe work
practices can practically eliminate most dangerous fiber exposures.
In other types of non-asbestos materials being used, we are starting to
experience a great deal of concern and some health problems.
1) Asbestos free calcium silicate — some brands show a rather large
amount of free silica. Silicosis could result.
2) Man-made fibrous insulation materials such as rock wool, mineral
wool, slag wool, fibrous glass, Kaowool, and others — we are
constantly receiving letters and phone calls from our local union
officers and our members complaining about severe dermatitis, eye
and ear infections and, of course, many upper respiratory tract
infections.
3) Extruded foam rubber products — exposure to toxic fumes from
adhesives and also solvents and chemicals used for cleaning hands,
tools and equipment.
4) Various insulation cements used for insulating pipe fittings,
equipment, pumps, etc. — contain mineral wool. Portland cement
and other materials cause severe skin and hand irritation
problems — very dusty when mixing - protective equipment must be
used.
5) Styrofoam, urethane — require respiratory protection in all
applications, mixing, spraying and foaming (.02 P.P.M. to M.D.I.
(methylene diisocyanate) and T.D.I.'s (toluene diisocyanate) in-
dependent fresh air supplied respirator) — emphysema from dust,
cutting.
6) We have in the past and will continue in the future to be exposed
to hot and cold tar pitches which we use to secure many various
types of insulation materials to equipment, pipes, tanks, etc.
We are also using many new types of adhesives, fasteners, electric
welding devices and other methods. Many of these insulation
products are being installed in plants, coke ovens, refineries,
chemical plants and other factories where a combination of toxic
or carcinogenic materials may be present.
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We strongly believe intensive Impartial independent research should be
conducted on any new insulation product before it is released for manu-
facturing and application. We in no way desire to be exposed to materials
or methods such as used in the asbestos fiasco.
As a member of the OSHA Construction Safety and Health Advisory
Committee I was appointed to serve on a special 5-man sub-group to review
the current statistics and regulations and to draft new language that would
allow the existing statistics to be applied to construction. This deliber-
ation took approximately a year and the finished report is now in the process
of being approved, rejected or modified by the Assistant Secretary of Labor,
Eulah Bingham. This report will also apply to any future health statistics.
Perhaps between this report and the new OSHA Construction Department led by
Mr. Stephen Cooper and the Toxic Substances Control Act, any new materials
in our industry will be fully analyzed and proper precautions can be taken
preventing any new rash of occupational disease.
More legislation can and should be enacted and enforced to protect the
working people from the unscrupulous manufacturer or employer who puts
profits ahead of human lives.
MR. JAMES F. REIS
As was evident from the product sessions and round table discussions
earlier today, one of the major points that industry has tried to convey to
EPA and CPSC in relation to their rulemaking on asbestos and their efforts
to develop information on substitutes is a basic precept of the free enter-
prise system: that is,
"If substitutes for asbestos and asbestos products were
technologically and economically feasible, the market
would have readily adopted them."
Incorporated into this. statement are many pressures that industries
using asbestos have faced over the past ten years. Among them are:
1. the increasing price of asbestos
2. the cost of asbestos products vs. substitute products
3. the availability of asbestos vs. substitute materials
4. the cost of meeting existing regulations
5. the concerns of industry due to the uncertainty created by
regulatory agency action and/or lack of action
6. the concern of industry for the health of its workers
7. the concern of increased potential liability for users of
asbestos
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8. the increased cost of insurance
9. the increased adverse publicity some of which we feel has been
unfairly generated by the regulatory agencies
With all of the above factors serving as incentives for industry to
remove asbestos from its products or to find replacement products, why in
1980 does much of U.S. industry and in fact world industry continue to use
asbestos and asbestos products.
The answer is three-fold. First, to date, many substitutes have not
proven to be economically and/or technologically feasible.
Second, there is a significant body of medical evidence that demon-
strate that asbestos when used properly need not present an occupational
hazard in the workplace nor a hazard to the general public.
And the third explanation which will be addressed tomorrow and
Wednesday at this workshop is that of all the environmental agents used in
industry today, probably more is known about the health effects of asbestos
than any other product. Industry, as well as EPA and CFSC, has no desire
to manufacture products that in many cases are more expensive and may exhibit
poorer performance, just to find out that these products may present a long
term adverse effect on the health of workers or the general public.
A case in point is the introduction by DuPont in the early 1970's of
a product called "Fybex", a potassium titanate fiber promoted as a replace-
ment for asbestos in plastics and friction materials. I have never seen an
estimate of the cost of the research work done by industry in evaluating
this material as an asbestos substitute, but it would probably be conserva-
tive, based on the numbers shown by Mr. Brunhofer this morning, to talk in
millions of dollars. In 1974, DuPont withdrew this material from the market
because initial testing indicated it could present a health hazard to humans.
A laudable move on the part of DuPont; but a real life example of the
problems that must be anticipated in the search for substitutes for asbestos.
The asbestos industry has made a conscientious effort to categorize
asbestos products in order to identify those products which can be used
safely and those products which present the greatest potential for un-
controlled release of respirable asbestos. The product categories the
industry adopted are:
Encapsulated - Those products which during any reasonable foreseeable
use do not release fibers in concentrations in excess of the mandated
OSHA limits. In many cases fiber release from these products is
below detectable limits - that is, below 0.1 f/cc.
"Locked-in" - Those products which do not release fibers in concen-
trations in excess of the mandated OSHA limits when fabricated and
installed using proper work practices and/or tools.
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Friable - Those products which can release fibers in excess of the
mandated OSHA limits during routine handling and use.
It is in the friable category of products where Johns-Manville has
expended its efforts to develop substitutes and where we feel the
substitute approach is the best solution to eliminating potential hazardous
exposures.
Today, all calcium silicate block and pipe insulation produced by
Johns-Manville does not contain asbestos. Nor do any of our insulating
cements. As a supplier of asbestos* we discontinued the sale of asbestos
to the joint cement industry in 1976 and in some cases worked with the
manufacturers to assist them in finding substitutes.
It is rewarding to see that EPA and CPSC have chosen to devote half of
this workshop to the health aspects of substitutes. The asbestos cement
pipe industry, in particular, has been extremely concerned with EPA's
hesitancy toward taking a balanced approach to studying the health risks
associated with all types of piping materials used for potable water
supplies. Despite a significant body of evidence indicating that there is no
danger to health from drinking water transported through asbestos cement
pipe, EPA continues to caution states and municipalities about using this
product. It would seem reasonable that similar precautions should be issued
for galvanized iron, PVC, and asphalt and coal-tar lined iron and steel
pipe, all of which can contribute minor amounts of known carcinogenic agents
to water supplies.
All carcinogenic agents conform to certain accepted biological principles.
There is nothing unique about asbestos, except that it is ubiquitous in the
environment and much is known about it. There is no valid reason, scientific
or otherwise, to treat asbestos differently from any other carcinogen.
If EPA plans to eventually ban the use of asbestos and encourage or
mandate the use of substitutes for asbestos, then it is logical to assume
that the agency intends to apply this policy to all carcinogenic agents
regulated under the Toxic Substance Control Act. Any valid economic
evaluation of the impact of this regulatory policy must be extended to
include all carcinogenic agents and not just asbestos. Any narrower analysis
would be discriminatory.
It is Johns-Manville's position that products which contain asbestos
in an encapsulated or locked-in form can serve a useful function in our
modern technological society and that these products when used properly, do
not present a hazard to the health and safety of workers or the general
public. The many valuable products made with asbestos should not and cannot
be regulated out of existence unless there is a demonstrated and overriding
benefit to the public in doing so.
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MR. BARRY CASTLEMAN
As you know, most of the products in the asbestos industry are quite
old. The patents for asbestos insulation and roofing predate 1890.
Asbestos-cement was introduced at the turn of this century.
Mr. Manville, who ran the Johns-Manville Corporation for the first
quarter of this century, was particularly proud of the fact that he never
spent a dime on research laboratories.
My own interest in asbestos started in 1970. I was in graduate school
learning about air pollution. My background is in chemical engineering. I
was just looking for something interesting to study, and I tripped over
asbestos. I took a look at the way they were spraying it on the buildings
for construction, all over the City of Baltimore where I was in school, and
I thought, "Doesn't anybody know that stuff causes lung cancer, and
mesothelioma? Doesn't anybody know that the neighbors of asbestos factories
get mesothelioma and that the family members of asbestos workers get meso-
thelioma just from the dust that walks home on the guys' clothes? And people
that live near factories — children that have played on dumps —" this was
all in the medical literature in 1965.
This medical literature was based on experiences with the asbestos
products that had long been in manufacture by the companies that were in
that business. Were they willing to sell less asbestos to save people's
lives?
The gentleman from the Navy might have more concern if he saw the side
of the use of asbestos that I have seen. I am involved very often in
litigation involving people who worked in Navy yards, and have developed
cancer and asbestosis as a result of — sometimes just a few summers of
work there.
While visiting NIOSH in 1974, I was told a curious story. One of the
inspectors had gone to a Raybestos-Manhattan plant and seen a dry-weaving
operation right in the middle of the floor, and the rest of it was wet
weaving. The inspector had asked the plant manager how come they do not
shut down that dry weaving operation, it was throwing dust all over the
plant. He was told, "We have specifications from the Navy requiring so
many threads to the inch, which, in effect, specifies dry-woven asbestos
cloth."
NIOSH went to the Navy and said to me that they were just told to get
lost when they told the Navy to do something about the specifications.
By this time I was working for environmental groups, so I dashed off
a quick petition to the Secretary of the Navy, and just to make sure he
read it, I told Jack Anderson a little bit about this story and he wrote
something, too. This is one of many ways that I learned to operate in
trying to deal with these hazards, as an individual.
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The attitudes of the industry have fascinated me. The only voluntary
removal of asbestos from a single product was children's modeling clay
after Dr. Irving Selikoff found that something like 50,000 pounds of
modeling clay used by the elementary schools of New York was 50 percent
asbestos. They were making puppets with asbestos, and it was even in the
Girl Scout Handbook how much asbestos to use to make puppets.
To this day, the only product that I know being voluntarily written
off as an unacceptable use of asbestos by the asbestos industry at large
was modeling clay.
Five years later, in 1976, a woman in West Chester, Pennsylvania, was
making modeling clays for elementary schools, using Johns-Manville asbestos
that she bought from a distributor. I spent the next several years trying
to convince Johns-Manville not to sell its product through distributors
because Johns-Manville can not tell the distributor whom not to sell it to.
And since only 2 percent of their sales was to a distributor, I thought
they could easily do without it.
Johns-Manville opposed the ban on drywall spackling, as did the
Asbestos Information Association and Union Carbide, despite the fact that
10,000 tons of asbestos per year was used in spackling compounds. The
lungs of drywall workers on X-ray are as damaged as those of insulation
workers, according to recent medical reports.
As for substitutes, I am extremely pleased to see that there is now
such an interest in developing substitutes. I mean money, research and
development resources of some of the largest corporations in this country,
devoted to finding substitutes for asbestos. This has led to widespread
substitution of asbestos in insulation; and break-throughs are now being
made in friction products, packings, textiles, plastics, and fiber-cement
products, to name the more prominent cases. It is about time, and I am
happy to see that.
I think the most crucial aspect of implementing substitution is the
availability of substitutes. The EPA cannot write regulations unless
you people come forth with viable, commercial substitutes for asbestos,
with products that are quite reasonably capable of replacing asbestos,
considering the public health hazards of asbestos and the hazards of the
substitutes.
I have never heard of a single substitute for an asbestos product that
could rival asbestos for hazard. I am sure more needs to be known about
that, but we still need to decide what to do today, while we are finding
out.
My personal hope is that we can prevent, world-wide many needless
deaths from exposure to asbestos.
One of the people who I am involved with in compensation proceedings
is a woman who worked as a secretary in a plant where asbestos-cement panels
were sawed up. She worked two floors below the cutting room of where they
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sawed up those asbestos panels. This woman has mesothelioma today. It
does not take that much exposure to kill.
Yet today I find near the affiliates in India, of the Johns-Manville
Corporation and British firm Turner and Newall, conditions which you would
not believe, conditions which we thought went out with Merewether's reports
in 1930. I have pictures of a two-year old child sitting on an asbestos
cement waste dump right in front of his house beside Johns-Manville
affiliate in Ahmedabad. Houses in the neighborhood are built of asbestos
cement waste, and untreated wastewater pours its opaque burden into the
surface waters of the region.
After hearing what I have heard today about the availability of
substitutes, I think we are headed toward a tremendous reduction in the use
of asbestos worldwide. People in a lot of countries are gearing up the
same as we are here. I think that the United States will probably lead the
way. Hopefully, Quebec will see the mistake that it is making, getting into
the asbestos business at this time.
In Ontario, Johns-Manville just shut down a plant making asbestos
cement pipe when the 170 workers went out on strike. They said there is
not enough market for it and that they were shutting down other plants in
the United States, too. This plant in Toronto opened in 1947. Over the
last 20 years, 120 claims have been allowed for asbestosis and mesothelioma
and around 50 workers have died from asbestos diseases.
Meanwhile, Quebec is thinking of going into the asbestos business,
nationalizing its asbestos mines and being the death merchants of the
1980's, selling the stuff all over the world.
The availability of substitutes today convinces me that the use of
asbestos is really going to decline. It is not something that we have much
longer to wait for; it is really here. Tou have done a good job, and now
it's EPA's turn.
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DISCUSSION ON DEVELOPMENT OF SUBSTITUTES
QUESTION (Mr. Gurtowski): From 1935 to 1943, I was a chemist in the
American Manufacturing Company. We manufactured loaded insulation.
We used from 50 to 70 tons of the material a month. When I
checked back several months ago to see how many people had died
or had cancer, I was quite surprised to find there were two or
three people. Most of the people, 'they to^Ld me, died from over-
smoking. What had happened to the other 500 people who were
working in the plant with me?
ANSWER (Mr. Castleman): You are a fortunate man and you now have the
opportunity to provide some protection for people who are
currently in similar circumstances. Those circumstances are now
well recognized to be dangerous. Statistical studies on the
population establish that by working in circumstances such as you
described, you are running a high risk of acquiring adverse
health effects.
QUESTION (Chairman Guimond): I have a question that I would like to direct
to Mr. Moore, relative to the ASTM (the American Society for Testing
and Materials) developmental standards. One of the concerns that a
few people have expressed to me is that in some cases Federal (and
other) specifications require that varied amounts of asbestos be in a
product, whether or not the product really needs it for performance
purposes.
First of all, I would like your comments on these specifications, and
second, to what extent do you see the performance standards, either
standards by ASTM or other types of organizations, being useful in
determining whether or not a substitute will perform adequately.
ANSWER (Mr. Moore): Number one, my recollection is that ASTM
specifications do not specify formulation of the products. They
specify performance of the product. I am also of the under-
standing that it is now Federal policy that such a standard be
used wherever practical. The Federal government is using ASTM
standards in most cases.
QUESTION (Chairman Guimond): I was asking a broader question, and not
necessarily about ASTM; that is, do you know of other kinds of
stipulations such as Federal specifications that might be any
hindrance? Or secondly, do you think that we should broaden
standards into areas where they do not currently exist, so they
will help us to determine equivalence for performance?
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ANSWER (Mr. Moore): I am not really aware of any such standard existing.
With regard to general performance standards, the standards that
are now developed do provide for specific performance for various
types of materials and are significantly different depending on
the characteristics of the materials, such as plastics, in-duct
wiring, reinforced concrete, and asbestos-cement.
It is very difficult to come up with an overall generic specific-
ation that will cover all circumstances. It requires experience
in the field as to the performance of the parts of the various
products, and the particular conditions requiring one product
rather than another. It is very difficult to come up with an
overall standard.
QUESTION (Mr. Gurtowski): In many areas, we are concerned about thermal
insulation, should we worry about exposure to various solvents
in the chemical? And how is ASTM going to handle that particular
problem?
ANSWER (Mr. Moore): These standards are developed by committees of
people who are familiar with the characteristics of the various
products, so that information is, hopefully, put together in
development.
QUESTION (Chairman Guimond): Mr. Gurtowski, you were talking about the
transition to substitutes in aircraft in the Naval program. Are
you doing anything from the standpoint of first establishing
what performance you need and then searching for substitutes?
ANSWER (Mr. Gurtowski): Yes, we look at- the environment the product is
exposed to (temperatures, solvents, fluids) and then try to
find a substitute that has the same physical and chemical
properties. The substitute we find will have to have exactly the
same physical properties of the material we intend to replace.
In particular, one formulation that contained 6 percent asbestos
was looked at in the aircraft where the temperature did not
exceed 200°F. The specifications were very low, so through a
series of experiments, we developed a new formulation. In that
particular case, it was relatively simple. But for instance, if
we have to protect the pilot from a fire with temperatures that
will exceed 2,000°F what substitute are we going to use? The
other thing we worry about is if we use glass, it can break up,
and be inhaled into the lungs and could be just as dangerous as
asbestos fibers. This gives you an idea of some of the things
we have to do.
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I have one problem now where we have an asbestos cloth that is
impregnated with neoprene rubber. In, this particular case we
depend on the neoprene rubber to get overheated, char, and act as
a thermal insulator, in addition to giving us the protection
against fire. We have hundreds of materials which protect our
aircraft, such as polysulfide, polyurethane sealant, and others.
Many of these contain some form of asbestos, whether in a
powdered form or in various lengths. The asbestos provides needed
properties; at the same time the substance gives us the water
proofing we need to make sure that our aircraft flies safely with
our weapons systems.
In missiles, the temperatures quite often exceed 2,000 F, even
though it is just for a few seconds. What material are we going
to use? Glass will melt, other organic materials I do not think
will work either. We are not giving up the search for a substi-
tute, but the understanding is that we are not going to eliminate
asbestos altogether. That is something that will never happen.
QUESTION (Mr. Castleman): This question is directed to Jim Reis. I would
like to get a list of inappropriate or unfit uses of asbestos
from Johns-Manville, or from any other company. I was told by your
world fiber sales chief three years ago that such a list was being
developed, but I was never able to obtain it. I presume the sale
of fibers for uses that you consider off limits as well as the use
of your own fiber occurs. Does this apply world-wide or just in
a particular locality?
Lastly, if you have information on the vinyl chloride that leaches
from PVC pipes into drinking water, which the EPA ought to know
about in evaluating its alternatives to asbestos cement, will you
please submit that information. I would assume that you have done
some testing and I am sure that EPA would be interested in seeing
what you thought.
ANSWER (Mr. Reis): As far as appropriating uses are concerned, there
have been several presentations given by Johns-Manville people that
identified a number of appropriate uses. We looked at each of the
categories and made a conscientious effort to try to eliminate sales
to those categories which we identify as inappropriate.
QUESTION (Mr. Castleman): What are the categories that were inappropriate?
There could not be too many of them; can you remember?
ANSWER (Mr. Reis): I have listed several of them here and I could probably
go on. I do not have any desire to list them right now.
QUESTION (Mr. Castleman): Well, what are they: insulation, spackling com-
pound, children's clay, hair dryers? What else is an inappropriate
use of asbestos?
QUESTION (Chairman Guimond): Mr. Reis has indicated they are developing
substitutes in the areas where they feel asbestos was inappropriate.
Is it implied that you are or are not developing substitutes or
considering substitutes in the areas where you have locked-in
fibers or the encapsulated fibers?
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ANSWER (Mr. Reis): That is a particular point I did not mention, but
I think it is common business sense. I do not think there is
anyone in this room who uses asbestos today who is not looking at
potential substitutes. A hundred years ago, asbestos was not a
particularly common product in industrial use. It evolved over
that period of time; it has become very popular, and like many other
products in industry, we did not foresee the possibility that its
use would become a'lot less than it is today. So we continue to
look at substitutes. Obviously, Johns-Manville, as any other
company here that uses asbestos, is aware of the government
regulatory actions, and we will look at substitutes and evaluate
them from our viewpoint.
QUESTION (Mr. McCarthy): I am with Minerals Week. I would like to address
this question to the representative from the asbestos workers.
What are your feelings about being somewhat of a guinea pig for
potential health effects from replacements for asbestos. Are you
actively involved in ensuring that the laboratory tests meet speci-
fications before you start using those kinds of materials?
ANSWER (Mr. Steinfurth): We do have many materials analyzed by a well
known firm. If I mentioned the name, you would agree that they have
a good reputation, both in industry and government. I happen to
have two sons who are asbestos workers. They have been working
with a particular fibrous product in a nuclear energy plant. They
have been working seven days a week in a so-called spread room,
cable room and so forth. They came to iny house yesterday and I
could not recognize them because their eyes were almost closed
and their faces looked like they had the measles. I guess you
know now that they were working with Kayo wool. They were laying
it very gently in the cable area.
Of course the temperature in this spread room runs about 105 to
110°F. They did not have the proper safety equipment, respiratory
equipment and so forth.
We have also found that some protective clothing, which many people
call "paper coveralls," should not be worn in heated areas because
they induce heat stress and eventually heat prostration, or heat
stroke.
I am sorry, I missed parts of your question, please state it again.
QUESTION (Mr. McCarthy): Basically, I am looking for what the asbestos
workers might have available to them, to ensure that that kind of
result does not occur to workers in general. Is there a lobbying
effort on your part? Is the government actively soliciting some
prerequisite regulations on your behalf before it goes into general
use? Is there any intercommunication between you and specific
corporations that are looking at asbestos and categories they have
considered inappropriate uses?
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ANSWER (Mr. Steinfurth): We do not have that much involvement with some of
the current produces. In fact, this is supposed to be covered
under the Toxic Substance Law—let us leave it that way. Up to
date, you know ae well as I do, the law has not worked the way it
should have worked. We have to depend on ourselves and independent
scientists. We, in our organization, feel we can no longer take
the word of any industry-oriented scientist, after the problems we
have encountered with asbestos. We do analyze products, see what
they are made of, get the opinion from not only the person who
analyzes the products, but also from different authorities, such as
Dr. Selikoff and Dr. Cooper, who both do work for us and are able
to help us immensely.
QUESTION (Mr. McCarthy): If the workers find themselves in these kinds of
predicaments and if they really can not judge the effect of the
substitute without, perhaps, lengthy exposure experiments, what
state does the consumer find himself as far as exposing himself
to asbestos and to what extent can he approach the government or
industry, or, perhaps, an organized labor union to ensure his own
safety?
I mean, asbestos receives enough publicity that people are coming
to grips with it; consumers are looking for labels in areas before
they replace asbestos tiles, tools, etc. What about replacement
parts? Are consumers being led to believe that they are safe when
actually we have no evidence to the fact?
ANSWER (Mr. Steinf urth): What you say is true. Some consumers are led
to believe that some products are dangerous. We have had problems
with some products. I have to put it very gently and say that if
we do have a problem and the contractor or owner does not wish to
cooperate, we have methods to make them cooperate.
REMARK (Mr. Gurtowski): We have activities that we do at the Navy
Environmental Health Center related to all of these organic materials
to ensure that the workers are protected.
One of the things we find to be the worst culprit, as far as toxicity
is concerned, is that a man becomes so familiar with a product
that he gets careless. We have had several Fh.D.'s who had to
retire because of exposure. One man should have known better, but
he had worked with the material for so long that he got a little
careless and he paid for it.
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ROUNDTABLE DISCUSSION SESSIONS
The roundtable discussions were provided to give all participants a chance
to supply information on technical and economic substitutes for asbestos to
EPA. The roundtables discussed asbestos substitutes for eight categories:
friction materials, gaskets and packings, reinforced plastics, flooring,
paper and roofing products, textiles, asbestos-cement sheet, and asbestos-
cement pipe. These roundtable discussions were held concurrently from 3:30 -
5:30 p.m., the first day of the workshop.
A list of general questions about asbestos substitutes for asbestos was
distributed to all participants to help guide the discussions, followed by a
similar but more detailed list for each product category. These questions
and the summaries of the roundtable discussions follow on the succeeding pages.
1. What are all of the uses and applications in this product
category?
2. What fibrous or product substitutes exist for these
applications, products, and uses?
3. What are the technical performance characteristics of the
substitutes in this category?
4. What are the lifecycle costs of the substitutes in this
category?
5. To what extent can existing capital equipment be used to
produce substitute materials or products?
6. Would energy requirements be changed substantially by switching
to production or use of the non-asbestos material?
7. What are the performance standards or product specifications
required of a substitute? Would any of these standards be
unnecessary if substitute materials were used?
8. What research and development is underway in this product
category?
9. Identify any health and environmental effects_of the materials
used to substitute for asbestos in this product category. ~ .
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SUBSTITUTES FOR ASBESTOS FRICTION MATERIALS
1. What are the basic ingredients used in nonasbestos disc brake and
drum brake lining formulations? Of particular interest are the
materials used to substitute for asbestos. What are the physical
characteristics and size distribution of fibers used to substitute
for asbestos? ;
2. What are the performance characteristics and the problems associated
with the use of substitute products for drum brake linings contain-
ing asbestos? Do the non-asbestos pads provide adequate performance
in the categories of lining wear, noise, wet recovery, etc?
3. What non-asbestos friction materials are available for applications
other than in automobiles and light trucks (aircraft, heavy duty vehi-
cles, etc.)?
4. What problems hinder the commercial utilization of non-asbestos drum
brakes? Estimate research and development costs and time for develop-
ment of commercial non-asbestos drum brake linings. How long did it
take to develop non-asbestos disc brake pads?
5. If a new car is designed to use non-asbestos disc brakes are re-
placement linings for that vehicle also non-asbestos? What are the
problems associated with providing a replacement lining tor a car
which has been designed to use non-asbestos brakes?
6. What mechanisms are there for the transfer of technology to other
companies who manufacture brake linings? If the use of asbestos in
friction materials such as brake linings and clutch facings were
prohibited how would your company acquire the technology to manufac-
ture non-asbestos friction materials?
7. Identify any health and environmental effects of the materials used
to substitute for asbestos in friction materials.
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SUBSTITUTES FOR ASBESTOS GASKETS AND PACKINGS
1. The background Information report identifies two main types
of asbestos gaskets: compressed sheets and beater-add sheets. It
also states that asbestos packings are generally made from yarns
impregnated with a lubricant, and that packings may either be leak
proof (for valves) or permit leaking (for pumps). What other types
of gasketing and packing materials containing as.bes:tos exist?
2. Fiber substitutes for asbestos in gaskets and packings include silica,
graphite, and ceramic fibers, as well as some synthetic fibers:
aramids, Kevlar®, Teflon®, Gylon®, and Nu-Board. What other fibrous
substitutes are available? What non-fibrous substitutes are available?
3. How do available substitutes perform with respect to 1) resistance
to heat, 2) resistance to pressure and friction (in the case of
packings), and 3) resistance to chemical attack? Do synthetic
fibers perform better than the natural (silica or graphite) fibers?
How do non-fibrous substitutes perform?
4. The cost of substitute fibers ranges from .75 to 32 times the cost of
asbestos fibers. However, these are not lifecycle costs. How do the
cost of installation and maintenance frequency influence the lifecyele
cost of a substitute gasket or packing?
5. In the case of substitution of other fibers for asbestos in gaskets
and packings, can original equipment still be used in production of
the nonasbestos product? What are the projected costs of any equip-
ment modifications that must be made?
i
6. Would energy requirements be changed substantially by switching to
production or use of the nonasbestos material?
7. What performance standards or specifications are required of gasketing
and packing materials? Do substitute materials meet these standards and
specifications? Would any of these standards be unnecessary if sub-
stitutes were used?
8. The background information document lists a large number of non-
asbestos raw materials from which gaskets and packings may be fab-
ricated. What research is planned or underway to develop addi-
tional new materials?
9. Identify any health and environmental effects of the materials used
to substitute for asbestos in this product category.
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SUBSTITUTES FOR ASBESTOS IN REINFORCED PLASTICS
1. What are all of the major uses and applications in this product
category?
2. What fibrous or product substitutes exist for these applications,
products, and uses?
We know that glass fibers, carbon fibers, aramid fibers, clay, mica,
wollastonite, calcium sulfate and talc can be used to replace asbestos
fiber in phenolic molding compounds and other plastics. What other
materials can be used to replace asbestos in these plastics? We know
that the types of plastics that are used include phenolics, urea, melamine,
unsaturdted polyesters, diallyl phthalate prepolymers, epoxies, silicones,
polypropylene, and nylon. What other plastics are used to make rein-
forced plastics?
3. What are the technical performance characteristics of the substitutes in
this product category? Are there any applications for which no sub-
stitutes have been found? Have substitutes been found for phenolic
molding compounds in commutators and rotors for electrical and automotive
appliances? Is there data on the long term performance, particularly
durability, of these and other substitutes?
4. What are the life cycle costs of the substitutes? We would like information
on costs of production, maintenance, and replacement (i.e. product lifetime).
There can be a rather large variation in cost of filler material for plastics.
Does this cause any large variations in final product cost? If so, what
are they?
5. To what extent can existing equipment or processes be used to produce
substitute materials or products? If existing equipment or processes
must be modified to accommodate substitute production, what changes must
be made and what are the costs of those changes?
6. Would energy requirements be changed substantially by switching to pro-r
duction or use of the nonasbestos material?
7. What are the performance standards of product specifications required of
a substitute? Would any of these standards be unnecessary if sub-
stitute materials were used?
8. What research and development is underway or planned in this product
category?
9. Identify any health and environmental effects of the materials used to
substitute for asbestos in this product category.
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SUBSTITUTES FOR ASBESTOS IN FLOORING
1. What are all of the applications and uses of asbestos in this product
category: Are there any other types of asbestos containing flooring
other than floor tile and sheet flooring?
2. What fibrous or product substitutes exist for these applications, products,
and uses?
3. What are the technical performance~characteristics of substitutes in this
product category? Are there any applications for which no substitutes
have been found?
4. What are the lifecycle costs of substitutes? We would like information
on costs of production, maintenance, and replacement (i.e., product
lifetime).
5. To what extent can existing equipment or processes be used to produce
substitute materials or products? Would new equipment or processes be
required to produce or use nonasbestos vinyl flooring? If so, what
would be the costs of developing the new equipment or processes?
6. Would energy requirements be changed substantially by switching to
production or use of the nonasbestos material?
7. What are the performance standards or product specifications
required of a substitute? Would any of these standards be unnecessary if
substitute materials were used?
8. What research and development is underway or planned in this product
category? When do various companies project that they can develop
prototype substitute materials? When do they expect nonasbestos vinyl
products to be commercially available?
9. Identify any health and environmental effects of the materials used to
substitute for asbestos in this product category.
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SUBSTITUTES FOR ASBESTOS PAPER AND ROOFING PRODUCTS
1. The paper products that are listed below contain asbestos and have
multiple uses:
a. Flooring felt
b. Roofing felt
c. Beater-add gaskets
d. Pipeline wrap
e. Millboard
f. Electrical insulation
g. Commercial paper
- General purpose thermal insulation
- Muffler paper
- Corrugated paper
h. Speciality papers
- Cooling tower fill
- Transmission paper
- Electrolytic diaphragms
- Decorative laminates
i. Beverage and pharmaceutical filters
Are you aware of any other asbestos-containing paper products? What are
they and what are their uses?
2. The following substitutes exist for the paper products that are listed
above:
a. Flooring felt - potential substitutes that have been studied
include fiberglass, cellulose, Nomex®, other polymeric fibers.
b. Roofing felt - organic felt, fiberglass felt, single-ply
membrane felt.
c. Beater-add gaskets - ceramic, Teflon®, metals.
d. Pipeline wrap - saturated fiberglass, plastic tapes, extruded
epoxys, and resins.
e. Millboard - aluminasilicate ceramic fibers and inorganic or
organic binders, ceramic fiberboards.
f. Electrical insulation - aramid paper, ceramic paper.
g. Commercial paper - ceramics, cellulose, fiberglass.
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h. Specialty papers
- Cooling tower fillers - polyvinyl and polypropylene plastics,
cellulose, aluminum, steel.
- Electrolytic diaphragms - Nafion® membrane cell.
- Decorative laminates - glass, ceramic papers.
i. Beverage and pharmaceutical filters - cellulose, fibers,
diatomaceous earth, mixed wood pulp and paper.
What other fibrous or non-fibrous substitutes exist for these paper products?
3. Any number of the following factors may be considered in evaluating the
technical performance of these materials:
• strength
• decay resistance
• thermal resistance
• sound deadening
• water proofing
• durability
• economy
How do substitutes for the nine types of asbestos paper products mentioned
in question #1 perform relative to the factors listed above? Are there
any applications for which no substitutes exist?
4. Based on the background information report, the cost of substitutes seems
to be greater (up to 10 times) than the cost for asbestos products
(except for organic felt used in place of asbestos roofing felt). These
costs, however, are not lifecycle costs. What are the costs of substitutes,
Including transportation, installation, maintenance and replacement (i.e.,
product lifetime) costs?
5. Several asbestos paper products are manufactured using conventional
paper machinery. For example, commercial papers, roofing felt, and
electrical insulation are produced in this manner. Can substitute papers
be manufactured using the existing equipment? Do you foresee any
additional equipment costs in switching to non-asbestos substitutes?
6. What additional energy requirements do you anticipate for the production
of substitute products?
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7. One product specification that is consistently mentioned in the
summary report is "durability." What is your definition of a "durable"
substitute? What other performance standards do you consider to be
essential? Are there performance standards for the production of non-
asbestos paper products?
8. The summary report indicates that substitutes for the nine groups of
asbestos paper products either have been or are currently being developed.
What research and development is planned or underway that may effect sub-
stitutions for asbestos paper products?
9. Identify any health and environmental effects of the materials used to
substitute for asbestos in this product category.
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SUBSTITUTES FOR ASBESTOS TEXTILES
1. The three major uses for asbestos textiles are:
a. Fire resistant application in
(1) welding curtains
(2) draperies
(3) blankets
(4) protective clothing
(5) hot conveyor belts
(6) furnace shields
(7) molten metal splash protection aprons
(8) rocket and missile parts
(9) ironing board covers
(10) theater curtains
b. Thermal insulation in
(1) pipe wraps for safety protection
(2) stress relieving pads in welding operations
(3) protective covering for hot glassware utensils
(4) coverings for diesel engine exhaust lines
(5) flue sleeves
(6) braided walls in the construction of steam hoses
c. Electrical insulation in
(1) wires and cables
(2) arcing barriers in switches
(3) circuit breakers
(4) heater cords
(5) motor windings
Do you have any additional major uses to add to this list?
2. The major types of substitutes for asbestos textiles are fiberglass,
ceramics, organics, graphite, carbon, quartz, cotton, and special wool
blends. Can you add other substitutes to this list?
3. How do substitutes compare to the asbestos use or products in technical
performance?
Fire resistant materials: Which substitutes are effective at temperatures
higher than 1000°F (540°C)? Which substitutes are effective at lower
temperatures?
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Thermal Insulation: Fiberglass is effective at temperatures below 1000°F
(5AO°C) and ceramics at higher temperatures; however, these materials
may lack strength. How important is this quality for thermal insulation
applications?
Electrical insulation: Glass and organic materials can be used at lower
temperatures and ceramic materials and quartz are more effective at
higher temperatures. Glass is not suitable in applications where severe
flexing is involved. These materials tend to have low conductivity and
low density. Please comment.
4. What are the lifecycle costs of substitutes? Consider costs of production,
maintenance, and replacement (i.e. product lifetime). Are there any
substitutes which are available but are not yet marketable because of cost?
Would economies of scale reduce costs enough to make them cost competitive?
If so, which ones would become cost competitive?
5. Can substitutes for asbestos textiles be made or used with existing
equipment and processes? If changes are required what are the costs of
these changes?
6. Would energy requirements be changed substantially by switching to
production or use of nonasbestos materials?
7. What are the existing performance standards or product specifications for
textile applications? For example, asbestos fire insulation has a UL fire
rating. Can substitutes meet the same standards? Would any of these
standards be unnecessary if substitute materials were used?
8. What research and development is underway or planned to effect sub-
stitution of other materials for asbestos? To what extent are recently-
developed or introduced substitutes such as Refrasil®, Thermo-Sil™,
Zetex™, Nextel® 312, Nomex®, Teflon®, Kynol™, Durette®, P.B.I.™,
Thermo-Ceram™, Fiberfrax®, Celion®, Celiox™, Alphaquartz, and Norfab®
being produced and sold in the United States? How long did it take to
develop these materials and what were the development costs?
9. Identify any health and environmental effects of the materials used to
substitute for asbestos in this product category.
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SUBSTITUTES FOR ASBESTOS-CEMENT SHEET
1. The four major types of asbestos-cement sheet (a/c sheet) are
a. Flat sheet, used in
(1) Industrial, commercial, and residential buildings
(2) decorative paneling
(3) cooling towers
(4) laboratory table tops
(5) ovens, safes, heaters, etc.
b. Corrugated sheet, used in
(1) electrical equipment as an insulator
c. Siding shingles
(1) industrial and agricultural buildings
(2) lining for waterways and canal bulkheads
(3) cooling towers
«
d. Roofing shingles
Do you have any additional major applications or uses to add to
this list?
2. The major types of substitutes for a/c sheet are glass-reinforced
concrete, cement-wood board, other types of fiber-reinforced concrete,
and wood products such as hardboard. Can you add any additional types of
substitutes for a/c sheet to this list?
3. What are the technical performance characteristics of the substitutes in
this product category?
Glass-reinforced concrete, although its overall strength is high,
may be weak at high temperatures. It may also be difficult to
machine well. Please comment on any other limitations on the
performance of glass-reinforced concrete sheet.
What are the performance characteristics of other substitutes for
a/c sheet, including cement-wood board, wood products, alumina-
silica products, and fiber-reinforced concrete?
For what a/c sheet applications are there currently no available
substitutes? Lab tables and some electrical applications (which?)
may be examples of applications for which there are currently no
available substitutes.
4. What are the lifecycle costs of various substitutes for a/c sheet? Are
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there any substitutes which are available but are not yet marketable
because of cost? Would economies of scale from increased production of
the substitutes mitigate this problem?
5. To what extent can capital equipment currently used for a/c sheet
production be used to produce fiber-reinforced concrete or other sub-
stitutes for a/c sheet?
6. Would energy requirements be changed substantially by switching to
production or use of the nonasbestos material?
7. What are the performance standards or product specifications required of
a substitute? Would any of these standards be unnecessary if substitute
materials were used? For example, a/c shingles have a U.L. Class A fire
rating. Can substitutes match this? Is this fire rating necessary?
8. What research and development is underway or planned in this product
category? To what extent are recently developed or introduced sub-
stitutes such as fiber-reinforced cement sheet and wood products being
produced and sold in the United States?
9. Identify any health and environmental effects of the materials used to
substitute for asbestos in this product category.
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SUBSTITUTES FOR ASBESTOS-CEMENT PIPE .
1. Identified uses of asbestos-cement pipe are pressure pipe (water mains,
laterals) and non-pressure pipe (sewer mains,drainage and irrigation
pipe, and electric and telephone conduit). What other uses of asbestos-
cement pipe exist?
2. Only glass fiber is currently employed as a reinforcing fiber in a
commercial asbestos-cement pipe product. Have any other fiber replace-
ments for asbestos in asbestos-cement pipe been identified? Other than
ductile iron pipe, concrete pipe, plastic pipe, and vitrified clay pipe,
are there any products that may be used to substitute for asbestos-cement
pipe?
3. What are the technical performance characteristics of the substitutes in
this category? What implications do characteristics like pipe flexibility
and burst strength have for the use of substitutes?
4. What are the lifecycle costs of the substitutes? We would like information
on costs of production, transportation, installation, maintenance, and re-
placement (i.e., product lifetime).
5. Could existing equipment or processes be used to produce glass reinforced
cement pipe? If changes in equipment or processes are necessary, what
would be the costs of those changes?
6 Would energy requirements be changed substantially by switching to produc-
tion or use of the nonasbestos material?
7. What are the existing performance standards or product specifications
required of asbestos-cement pipe? Do substitutes meet these standards?
Would any of these standards be unnecessary if substitute materials were
used?
8. What research and development is underway or planned in this product
category?
9. Identify any health and environmental effects of the materials used to
substitute for asbestos in this product category.
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SUMMARY OF THE ROUNDTABLE DISCUSSION
ON FRICTION PRODUCTS
PANEL MEMBERS
Jeatmette Wiltse — (Moderator) EPA, Office of Pesticides and
Toxic Substances
Al Colli — EPA, Office of Pesticides and Toxic Substances
Jim Hughes — EPA, Office of Pesticides and Toxic Substances
Jeannette Wiltse of the Environmental Protection Agency (EPA) described
the EPA's interest in comments on the issues listed in the handout or any
other information the participants in the discussion might want to convey.
She asked about the role of substitutes in the aftermarket when, for instance,
a friction material has an asbestos substitute. Mr. Drislane of the Friction
Materials Standards Institute (FMSI) replied that some replacement brakes for
semi-metallic original equipment brakes are nonasbestos and others contain
asbestos. He suggested that perhaps after several years, like will be replaced
with like.
Jeannette Wiltse of EPA asked how brake repair people know what to use
as replacement parts? Mr. Drislane replied that the field has this informa-
tion but the concern of the brake repair shop people is about product
liability.
Jim Hughes of EPA asked if small brake manufacturers could have capital
equipment and financing problems in converting to nonasbestos friction pro-
ducts. Mr. Drislane of FMSI replied that this will be a real problem for
some of the smaller manufacturers. Jim Hughes asked if plant closures would
result. Mr. Drislane replied that he could not predict that, but suggested
that in 5 years most people will be using the same type of material.
Mr. Ward of General Motors (GM) said the entire brake system is designed
as a unit. The engineers who make substitutes indicate that problems could
result if replacements are not made of materials similar to those of the
original equipment.
Mr. Brunhofer of Bendix said that the friction material is part of an
overall system. Substitution should be studied carefully or else problems
in safety or wear may develop. The aftermarket materials have been developed
over a long period of time. He said that as you phase into a revolutionary
period problems may develop, but that time is a big healer.
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Al Colli of EPA said that some firms apparently do not have the techno-
logy to manufacture nonasbestos brakes. Do major manufacturers of nonasbestos
brakes have provisions for licensing or do they hold the technology as
proprietary?
Mr. Brunhofer of Bendix replied that his company has many license agree-
ments today, but they are for the international market and they usually
include territorial exclusions. Bendix is not aggressively pursuing licensing
but has not excluded the possibility. Significant amounts of company funds
have been expanded to develop new technology.
Jim Hughes of EPA said that EPA is concerned about the effects of possible
regulation of asbestos on small business.
Mr. Drislane of FMSI commented that semi-metallic brake development began
in 1962 before asbestos was an issue. It is utilized because it meets market-
place needs. Mr. Rosenberg of Borg Warner said that they manufacture manual
clutches which use friction materials containing 50 percent asbestos. Several
years ago they made a corporate decision that they should develop asbestos
free friction materials. He said that they did not do this because of environ-
mental concern from asbestos, but because they wanted to protect our employees
from occupational exposure. He said that several million dollars have been
expanded and they are close to their goal. They may enter license agreements
or manufacture in Brazil.
Al Colli of EPA asked what tests or design consideration go into brakes
manufactured for the marketplace. Mr. Ward of GM replied that if you used an
asbestos lining instead of the currently-used linings, the car would still
stop safely. However, the life expectancy of the braking system would be
poor.
Al Colli of EPA asked if more stringent- government requirements on
original equipment brakes as opposed to brakes for the aftermarket would
result in the manufacture of asbestos replacement for semi-metallics. Mr.
Ward of GM replied that when dealing with smaller cars, the size of the
braking system may be a consideration. Mr. Brunhofer of Bendix commented
that semi-metallics have been designed into the system because of their high
temperature properties. Organic materials (such as asbestos) have high wear
rates above 350°; Semi-metallics can withstand temperatures of 650° to 700°.
Most vehicles in the past operated in the 250° to 400° range. Temperatures
of the new front brakes on small vehicles may exceed 400°. Wear is greater
if you substitute an organic for a semi-metallic material. The difference
is greatest with a small compact car with a solid rotor. Also, you will not
pass SAE (Society of Automotive Engineers) or federal fade requirements on
many small vehicles with a solid rotor. If you substitute an organic material
for a semi-metallic, you can also develop brake lock on slippery surfaces.
Mr. Chastine of Abex supported what Mr. Brunhofer of Bendix stated by saying
that Abex does not compromise quality in the aftermarket.
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Mr. Burgess of the Wheeling Brakelock Manufacturing Company said that they
do not have the capacity or know-how of GM or Abex, but that they start where
those companies leave off. Wheeling Brakelock makes very large brakes for
industrial equipment. They make brakes that weigh up to 75 pounds, are 5
inches thick and 120 inches in diameter. Mr. Burgess said that the asbestos
they're using is 40 cents per pound, but the stuff they have to replace it
with is $8.00 per pound. Also there are problems with molding.
Jeannette Wiltse asked how big this market was, and asked if substitute
materials had penetrated the market. Mr. Burgess of the Wheeling Brakelock
Manufacturing Company replied that there had been no market penetration by
manufacturers of substitutes. He said this is a highly specialized business
with only 5 companies left out of 20 several years ago.
Jeannette Wiltse asked if substitutes had ever been tried in these
applications. Mr. Burgess of Wheeling Brakelock Manufacturing Company replied
that his company gives all its money to EPA and OSHA (Occupational Safety and
Health Association) so they have nothing left. The size of the market is
small compared to the auto market.
Jim Hughes of EPA asked approximately how much asbestos does your company
use? Mr. Burgess replied that he did not want to say, but that EPA could
find out from Canadian records.
Mr. Ward of GM said that many industrial machines have asbestos brakes
that are essential to industry.
Jeannette Wiltse of EPA asked what are the performance characteristics of
nonasbestos drum brake linings—noise, wet recovery?
Mr. Brunhofer of Bendix replied that there are four main categories for
design considerations—friction stability, wear, effect on opposing surface
and noise. There is information in the literature on the materials that can
be used. Nonasbestos drum brakes have slightly higher friction but approxi-
mately equal wear if engineered properly. They have acceptable mating surface
wear, but noise is a problem.
Someone asked why American manufacturers do not make cars with four
wheel disc brakes like foreign car manufacturers. Mr. Brunhofer replied that
the answer was cost. Rear brakes have become parking brakes in many
applications.
Mr. Burgess said that every brake they manufacture has greatly different
design requirements.
Al Colli of EPA asked how the design criteria for all these applications
is determined. Is it an art or is there a scientific basis?
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Mr. Burgess of the Wheeling Brakelock Manufacturing Company said the
manufacturer has a starting range for coefficient of friction and it is trial
and error after that. You have to have the right brake block for the job.
Mr. Moulton of DuPont said that he would like to make a comment on Kevlar®
aramid fibers manufactured by DuPont. He said that Kevlar® has high tensile
strength, frictional stability, and excellent durability. It is used in disc
brake pads with wear levels between that of asbestos and semi-metallic mate-
rials. Kevlar® is being used in experimental drum brake linings and wet fric-
tion papers. Kevlar® does not score mating surfaces. It is used in manual
transmission for the Mercedes, Audi, and Porsche. The fiber is available in
a short pulp form at $3.75/lb. Only small amounts are required with deep
filler materials so that the cost is between 20 percent and 40 percent greater
than for asbestos with the lifetime cost approaching that of asbestos.
Mr. Brunhofer of Bendix said that their company went ahead on a crash
basis because of pending OSHA (Occupational Safety and Health Association)
regulations during the last 3 years. If the development had been over a
longer period of time they might have investigated other materials.
Jeannette Wiltse of EPA asked if new tooling and equipment is required
for nonasbestos brakes.
Mr. Brunhofer of Bendix replied that some new equipment is required for
manufacturing disc brakes. Different materials require different equipment.
For nonasbestos drum brakes, radical changes in processing may be required.
Jim Hughes of EPA asked how the life cycle costs of nonasbestos brakes
compare with asbestos.
Mr. Brunhofer of Bendix replied that life cycle costs have not been
taken into account. He said that semi-metallics have higher life cycle costs
than organics; but the former brakes are smaller and lighter, therefore
result in higher fuel economy.
Al Colli of EPA said that in 1985 all disc brakes on new cars will be
nonasbestos. We know that Bendix, Delco, and Abex have the technology. What
plans to the other companies have to obtain the technology?
Mr. Morris of Alfred University said that more basic research should be
done on substitute fillers to tailor characteristics to meet asbestos
applications.
Jeannette Wiltse of EPA asked how extensive is the basic research on
substitute materials.
Mr. Morris of Alfred University said that in the past several years they
have had three contracts in the friction area. More work should be done.
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Mr. Melner of Jim Walter Research said that he represents a company that
manufactures asbestos replacement material. They contracted to manufacture
about 16 million pounds of the material because of rumor or fact on regulations
pending on asbestos. If their substitute material works, they are concerned
about possible effects from it. He said that they have not received any
guidance from government regulatory agencies. As a supplier they are about
to commit a quarter of a million dollars for testing.
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SUMMARY OF THE ROUNDTABLE DISCUSSION ON
SUBSTITUTES FOR ASBESTOS GASKETS AND PACKINGS
PANEL MEMBERS
Hugh Spitzer — (Moderator), CPSC
Pat Harrigan — EPA, Office of Pesticides and Toxic Substances
Kirk Johnson — EPA, Office of Pesticides and Toxic Substances
I am Hugh Spitzer, Project Manager of Asbestos Products at CPSC. We
will proceed from the presentation given by Steven Koehler in the Work
Session on Gaskets and Packings. You have received an agenda listing ques-
tions around which we want to center our discussion. I will not go question
by question, but there are topics I do wish to cover. Also, you may have
questions on materials that Steven Koehler did not cover. And lastly, and
most importantly, I want to address the health and environmental effects of
the substitutes.
Hugh Spitzer asked if there are gaskets and packings made from any
other materials other than those mentioned by Steven Koehler in his presen-
tation on gaskets and packings.
Steven Koehler of Green Tweed Packing Company said that a few sub-
stitute materials that he did not mention in his speech were fiberglass and
ceramic fibers, each bound together with teflon suspensoids-"-Mylar© is the
copy-right name. Fiberglass, however, is too abrasive and brittle for use as
dynamic pump packing.
John Arena of Combustion Engineering said that in the first question on
the agenda you state that gaskets are impregnated with a lubricant. He said his
company manufactures a rope gasket which is 100 percent fiber, with no lu-
bricants or other additives, as it is intentioned for static service.
Steven Koehler said that is correct. The first question we address this
afternoon should be on uses of fibers. Ceramic wicking is one such use.
They are for basically static service-door gaskets, etc.
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Bill Timmons of Celanese Corporation said that Celanese has just begun
to market a fiber. Preox (PAN) is an intermediate material which is avail-
able commercially. The main cost factor in the production of carbon fibers
is a 50 percent yield loss. The fibers produced from these intermediates have
no yield loss, which therefore reduces the initial production cost disadvantage.
Preox is a precursor to a carbon product. Bill Timmons addressed a
question on brittleness saying that these fibers have over 10 percent elon-
gation. Next, he was asked about the fibers' behavior in response to ranges
of temperature. He responded that the conversion to carbon begins around
300°C, with a corresponding change in volume.
Steven Koehler asked Mr. Timmons to define Preox. Mr. Timmons replied
that the carbon fibers currently used in packings are based on rayon precur-
sors, which have only a 20-30 percent yield. With Preox, Celanese uses the
fiber itself (trade name Celiox), therefore, loses less in the production
process. Polyacrylonitrile precursors (PAN) would result in a 50 percent
carbon yield. These intermediates have a six member ring cross-linked ladder
structure.
Hugh Spitzer asked if he had any literature on this material. Mr. Timmons
replied that he did not have it with him but could get it that day or the next
day.
Ted Merriman of DuPont de Nemours Company, Textile Fibers Section thanked
Steven Koehler tor Discussing Kevlar® in packings. Dr. Merriman discussed
Kevlar®, saying that it is an aramid fiber which is now used in noncontinuous
forms in gasket replacements and other asbestos uses. Kevlar® pulp, produced
in a process similar to wood pulping, results in a slurry material with short
fibers of random length. This material is amendable to use in wet or dry
processes. Typical beater-add applications are a natural for this material.
Kevlar® is generally considered to be expensive. However, the pulp is priced
at around $3.75 per pound, a less drastic difference from the cost of asbestos
fibers.
Steven Koehler asked if Dr. Merriman knew about Kevlar® in heated water
under pressure. He asked if there were any known problems with breakdown of
tensile strength at, say, 300°C.
Ted Merriman said he had not done experiments with 300°C water.
They have used 212°C water with no breakdown. Kevlar® begins to breakdown
at 400°C, through irreversible oxidation. The products of degradation depend
on the process; i.e., conditions of degradation; mostly carbon is produced. Any
other products are proprietary information. When Mr. Koehler asked about the
likelihood of glassification, Dr. Merriman replied that Kevlar® does not sub-
lime. When asked about possible volatility of Kevlar®, Dr. Merriman replied
that there are volatile products of the degradation process. When asked if the
pulp process is a shearing process in water, Dr. Merriman replied that the
^process is a standard papermaking technology. He said that if it works for
wood products, it will work for Kevlar®. He said that he represented the
Kevlar® Research Group in Maryland and the Wilmington, Delaware Chestnut Run
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Site. When asked about pH, Dr. Merriman replied the Kevlar's sensitivity to pH
may limit its use as a substitute for asbestos-cement pipe. He said they
have not determined pH ranges yet.
Steven Koehler said that they had identified Kevlar® pH range as between
3 and 11. However, compression of the material may increase friction, heat,
and therefore, wear on the material. This in turn would increase any degradation
that may be caused by the presence of acid.
Ted Merriman said that it depends on whether you are in a high shear
environment or not. Steven Koehler agreed, saying that pH ranges can depend
on the pressure involved.
John Zeltz of the Victor Division of Dana Corporation said that the
volume of this segment of the industry is in service gaskets. He disagreed
with the assumption that there are technical substitutes for gaskets in areas
related to engine products. He said that one cannot predict that a new prod-
uct will be usable in those uses especially in cylinder heads or service
manifolds.
Steven Koehler said that the substitutes would probably function, but
the question is whether the new product is cost-effective. There are avail-
able substitutes that can be used.
John Zeitz replied that substitute gaskets would have to be designed for
each specific application and mentioned possible problems with load difference.
Bill Olden of Union Carbide said that they have graphite materials used
for head gaskets that are flexible on any engine.
John Zeitz expressed doubts about, the service of these graphite materials
on new designs.
Mickey Hosmer of Jim Walter Resources said that they produce fibers at a
cost of 25 cents per pound, much cheaper than longer fibers. John Zeitz asked
about the length of these fibers. Mr. Hosmer replied that they have a 40-60
percent aspect ratio.
Gordon Yuellig of Proctor and Gamble asked how many substitutes meet FDA
regulations for contact with food, drugs, cosmetics, and medical devices.
Steven Koehler replied, "One: Teflon®". Mr. Kelly said they have been
trying for years to find components of packings that will meet with FDA
regulations.
Al Diangelos said that Gore-tex, a PTFE fiber has also been approved;
however, this is also a Teflon® derivative.
Mr. Yuellig asked what we would do when we need a material that has a
temperature range above the 400°C range of Teflon*. Steven Koehler replied
that possibly metal gaskets could be used. Mr.Yuellig said that that is a
very poor substitute. (Later, he added that there are only temporary solutions.
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There is no satisfactory metal packing.)
John Halberta of Carborundum said that they produce Grafoil , ajElexible
graphite product. They said they are close to FDA approvaT~for itsT use re-
lative to food additives. They have one more hurdle (rat studies, etc.), which
they hope to clear in one more year. Aramid products, too, might be approved if
they are pushed.
Mr. Yuellig said that they had been trying to get rid of asbestos for
years but the FDA has not revoked its use. Mr. Diangelos said that Dr. Kreska
of the FDA is the man they have been working with.
Steven Koehler asked if we wanted to get rid of asbestos, but are not doing
so.
Hugh Spitzer replied that there is sometimes a fear among the regulatory
agencies that in banning one product, you unleash a worse product on the market.
Steven Koehler asked if asbestos has to pass standards such as those the
substitute must pass.
Hugh Spitzer asked, other than technical and FDA specifications, what
specific needs and performance standards do you have to meet?
John Zeitz replied that for temperature they need a standardized ignition
loss test which ASTM (The American Society for Testing and Materials) can
provide. They will be buying temperature resistance with this substitute.
It functions satisfactorily in the 600-800 (possibly to 1000°C) range.
Thomas Jackson of Johns-Manville Corporation said that there is an
existing standard now that goes up to 1500°C, which is now being revised;
whether it is adequate or not is unclear.
Al Gordon of Federal-Mogul Corporation said, regarding performance
standards and material specifications, ASTM is an agency operating under a
voluntary set-up. ASTM promulgates both material specifications and test
methods. F-8 is the Committee on Gaskets. Most standards are methods of
testing, also spelling out physical and certain functional properties. In
addition, a classification system is used to determine the appropriate
specification. Virtually all deal with non-metallic and non-rubber materials.
(D-ll is the Committee for Rubber Materials.)
ASTM was started at the request of the government, to develop standard-
ization. It is concerned with environmental issues. There may be an
opportunity for coordination: Any asbestos replacement materials would fit
into the classification system. If not, provisions have been made to allow
for incorporation of new materials. SAE (Society of Automotive Engineers)
engineers use ASTM's standards rather than duplicate their work. The military
also has a system set up to parallel ASTM's classification.
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Ted Merriman added that there is a military specification for graphite:
24503.
Steven Koehler said that there are military specifications for most
graded packing materials. Teflon filament, for example, is MIL-P-24377.
One problem here is that when the military asks for bids, they specify
materials, and will not accept substitutes. Someone said that there is now
a concerted effort in the Navy to get rid of asbestos.
John Zeitz said that the military is very slow here. In some cases,
they ask for asbestos.
Hugh Spitzer asked if those specifications spelled-out asbestos materials
only.
Steven Koehler said that performance characteristics are specified as
well. Some military specifications require asbestos; and these will probably
be the last to change. They purchase a lot of asbestos.
Mr. Yuellig said that substitution for asbestos means diversification.
Asbestos was so versatile. Using flax again is a regression; it is corrosive,
and does not function well at extreme temperatures.
Steven Koehler said that for pumping applications, long run, cost
effective, over-engineered, substitutes exist.
John Halberta said that they have a substitute and they would hate to
have to compete with flax.
John Zeitz said that they may be able to get more materials into the
market places. Finding direct substitutes is a minimal goal, although it
will not look so for the next five years. It will look like a snowstorm.
Steven Koehler said that when asbestos was discovered to have so much
versatility in its gasket and packing applications, some reliable old stand-
bys were overshadowed. He estimated that some 40-60 percent of asbestos
uses were unnecessary and were used simply because they were convenient.
Ted Merriman said that is the very point. Without much technical
background, the average mechanic knows about asbestos and knows it will work.
I agree that if you over-engineer with graphite, everything will work out.
Mr. Yuellig said if you are a small businessman without extensive
technology, asbestos is so versatile that it works for just about any need you
have. It will take a lot of good material to replace it, with the exception
of food products.
Louis Blecker of GAF Corporation asked what the health risk of asbestos
was. He asked how much exposure there was and does it warrant all this cost.
Hugh Spitzer replied that this workshop is concerned with substitutes for
asbestos. Louis Blecker asked if we needed asbestos substitutes. Hugh Spitzer
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replied that we are gathering information to find this out. Louis Blecker
said then why not use scientists, and competent people to study the problems
in a noncompetitive, nonadvocacy setting. Hugh Spitzer thanked Mr. Blecker
for his comments.
Herb Posner of NIEHS (the National Institute for Environmental Health
and Safety) said that they are looking at a number of real world situations
(brake linings, hair dryers, and so on) where there is an opportunity for
asbestos exposure. He said there is good evidence of the hazards of asbestos.
He said that as he saw it, the purpose of this conference is to identify where
exposure occurs and substitute asbestos with less hazardous substitutes. He
expressed concern that the health aspects of asbestos are always last on the
agenda, but acknowledged that perhaps that was alright because there was a
day and a half of health sessions scheduled.
Gordon Yuellig said he had a question for Mr. Posner. He said that
everything he had read, including Dr. Selikofffs study, stated that everyone
who has been exposed to asbestos was affected long ago. He asked how the
health hazards of asbestos exposure from hair dryers, et al, could be corre-
lated with exposures from the asbestos industry.
Herb Posner asked how long have hair dryers been used. Ted Merriman
asked how much asbestos gets out from these hair dryers. He said that GE
(General Electric) went along with the hair dryer recall because of adverse
publicity but later studies showed few, if any, fibers get released.
Herb Posner said that asbestos-cement sheeting, when misused in schools,
creates an exposure problem.
Derek Kuhn of the Richard Klinger Corporation said that he knew that
only substitutes are to be discussed, but asked if we could distinguish
between friable and encapsulated asbestos here.
Hugh Spitzer replied that he would prefer to limit discussion to sub-
stitutes for asbestos.
Derek Kuhn asked if there was any overlap when you consider encapsulated
asbestos hazards as compared to the friable non-asbestos fibers,
Hugh Spitzer said that it is not appropriate to discuss asbestos issues
now. He said the purpose here is to gather information on health effects,
etc. of other materials.
Herb Posner asked about uses of asbestos in gaskets and sealants. What
about workers who are exposed during servicing and installation? Someone
replied that that is not for this forum and the group should stick to dis-
cussing substitutes.
Hugh Spitzer said that perhaps they should go to the health effects
studies. He asked what results FDA (the Food and Drug Administration) had
been getting from their studies.
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John Halberta referred to Grafoil gaskets in his reply. He said that
his company (Carborundum) had to do earcinogenieity studies, and that their
results showed no effects on rats. For PMAs (polyaromatic hydrocarbons),
they have to demonstrate a concentration of 2 ppb or less. He said that the
sensitivity of the test had been the major difficulty in analyzing Grafoil
for the presence of PMAs. He said they could not find PMAs in flexible
graphite, so it was treated and then analyzed for PMAs. (No animal tests
were done.)
Hugh Spitzer asked if asbestos has been shown by the FDA to meet the 2
ppb hurdle. He also asked how this standard was set.
A participant replied that FDA set the 2 ppb standard.
Hugh Spitzer said that one problem with comparing asbestos to an organic
substance is asbestos is for all practical purposes not metabolized. Asbestos
can stay in the tissue, while other substances can be metabolized and
excreted.
Malcolm Fenton of Marrietta Resources International, Ltd. said they
manufacture Suzorite mica. He said when they tested a hypothetical process
and product for health effects, the data would necessarily be outdated within
five years time. By then, the use and exposure would be different. He asked
what the Federal agencies expected from health studies on substitutes.
Hugh Spitzer said that answer would be "safe material". Let me elab-
orate—regulatory agencies depend on scientific reports in assessing any
chemical or product with respect to health effects. Animal bioassays,
epidemiological studies and in vitro testing are all of value.
Malcolm Fenton commented that Bendix has spent millions of dollars on
health research; a development which is good both for the American people and
obviously for their company. He said that the job of the government was to
make sure that all brakes in the U.S. work. He asked if there was (any
possibility of) a bill in Congress to give companies like Bendix a tax break
on such work. He also asked about possible tax breaks for small companies.
Hugh Spitzer commented that there is a National Toxicology Program (NTP)
which recommends material to be tested. One criteria for material to be
reviewed by the NTP is large production/use volume. This is an established
program available out of NIH (the National Institute of Health) coordinated
with CPSC, EPA, and FDA. The government is concerned with industry concerns.
Malcolm Fenton said he assumed, then, that if a material is widely used,
it can be evaluated by government methods. He also asked about material not
yet widely used (which you would like to have widely used).
Hugh Spitzer replied that he should talk to the agencies to try to get
into a testing program. Herb Posner said that NTP is already trying to get
thousands of chemicals into at least short term tests as a start.
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Hugh Spitzer said that his advice was to keep after the agencies. He
suggested that companies should try to get chemicals into the testing program.
He continued by asking for information on the kinds of tests of materials
which are underway or planned (by industry).
A participant suggested to Hugh Spitzer that one of the other consider-
ations is energy requirements from producing and using these substitutes.
John Halberta commented that the silence indicated a general lack of
knowledge on testing. He indicated that participants (from industry) were
being asked whether they had done work on a product that might or may not be
acceptable by the government. He said that no one has any experience in
getting products approved. (Also, the economies of scale for asbestos re-
placement are not yet well understood. However, asbestos replacement
presents us with a marvelous opportunity, however elusive it may now seem.)
He said that (the government) had many definitive questions but that they could
only supply vague answers.
Hugh Spitzer asked for best guesses as to the needs of companies.
John Zeitz replied that they might require a multiplicity of systems,
but they would not have to start from scratch. Existing equipment will not be
thrown out as boat anchors.
A participant commented that the manufacturers of substitute fibers
should be asked that question, not the users. Someone commented that
capitalization for substitutes right now is not great.
John Halberta said that the question is whether you will have significant
enough incentives (e.g. tax incentives). Without incentives, new technology
will not be developed.
Louis Blecker said that they have just built a glass plant; there is a
tremendous need for capital.
Ted Merriman said that most of the emphasis this afternoon has been on
fibrous substitutes. Nonfibrous replacements will be important, too.
John Halberta said that their product, Grafoil , is nonfibrous.
Production may require new capital.
Hugh Spitzer asked if there were any further comments on nonfibrous
substitutes.
Frank Fry of Hollingsworth and Vose replied that the pressure will work
backwards from the user to the fiber supplier, each trying to conserve
capital. The incentive for change will come from the end users.
Hugh Spitzer said thank you very much for coming this afternoon.
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SUMMARY OF THE ROUNDTABLE DISCUSSION ON SUBSTITUTES FOR ASBESTOS
IN PLASTICS AND FLOORINGS
PANEL MEMBERS
Gale Wyer — (Moderator), CPSC
Terry Karels — CPSC
Will Stelle — EPA, Office of Pesticides and Toxic Substances
The meeting was attended by 20 to 30 people. The two hour session was
divided into two portions: the first on plastics and the second on flooring.
PLASTICS
The success of the search for substitutes for asbestos fiber depends
upon the function of the asbestos in each particular product and product
category. Asbestos fibers provide good tensile strength and possess good
thermal resistance. In addition, they also serve as a cheap filler for
plastic mixtures and make them easier to mold and to work. Many fillers are
available that are cheaper than asbestos but do not possess the same
strength or heat resistance.
If the thermal insulation or tensile properties of asbestos are necessary,
replacement may require using several materials together, such as a mixture
of mica and an organic material. If these special properties are not
necessary, organic fillers may be used, which are often cheaper than asbestos.
It was also noted that man-made fibers are generally more expensive
to produce than refined asbestos. Substitutes, especially man-made materials
are not as permeable as asbestos, to chemical constituents such as dyes.
Different, possibly more expensive means of production, could be necessary
when man-made fibers are used.
Manufacturers are often looking for products with greater reinforcing
and insulating properties than asbestos; this is due to increased demand for
high-performance materials by industrial users.
One view was that unless the use of asbestos is banned that it will
continue to be used since the product is effective and cheap.
Other views were that consumer pressure would eventually drive manu-
facturers away from asbestos and that this pressure was preferable to an
outright ban because the latter would cause serious economic problems for
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the industry. An example of this pressure is the increase in lawsuits.
Aother example is the shift away from asbestos use in hair dryers suggested
by CPSC.
One participant questioned the health hazards caused by using asbestos
in plastics and also stated that, regardless of the actual risk, the market
was demanding plastic products that did not contain asbestos fibers. Con-
sequently, he stated, the industry desired to move to substitutes where such
substitutes were available.
Eula Bingham of OSHA was represented as saying that there is a substitute
for every application of asbestos. Attendees argued that defense and
national security reasons could be used as reasons for continued use.
Participants said that an imposition of a ban would harm the industry.
Larger firms may gear up for substitutes; smaller firms may not be able to
gear up. Smaller firms cannot afford to tie up capital for research and
development and may be driven out of business.
A suggestion was made that CPSC and EPA contact plastics and other
professional organizations and associations for further information. Two
participants cited as a useful compilation of substitute information a recently
published book, Handbook on Fillers and Reinforcements.
FLOORING
Asbestos is used as reinforcement in vinyl asbestos (V/A) tile and as
a backing in vinyl sheet. The lengths of fibers used in each application
are different: the backing uses longer fibers, while V/A tiles use shorter
fibers.
Nothing more was discussed; members said that the industry is very
secretive and will not share technology. There are tremendous costs involved
in research and development for substitutes, and the firms will not share
expenses. Further, the firm that finds an acceptable substitute "stands to
make a lot of money" and may end up controlling the market.
Because no one was willing to speak about flooring, the attendees were
encouraged to submit written remarks.
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SUMMARY OF THE ROUNDTABLE DISCUSSION ON PAPER
AND ROOFING PRODUCTS
PANEL MEMBERS
Suzanne Rudzinski — (Moderator) EPA, Office of Pesticides
and Toxic Substances
David Bailie — Koppers Company
Nancy Roy — GCA Corporation
Christine Spadafor — EPA, Office of Pesticides and Toxic
Substances
June Thompson - EPA, Office of Pesticides and Toxic Substances
In response to a question by Ms. Rudzinski asking if there were any
uses of asbestos paper products for which there are no known substitutes,
Mr. Huseby, General Electric (GE) described an asbestos paper tape used in
GE transformers for which GE is seeking a non-asbestos substitute tape.
Ms. Carol Mansfield, Carborundum, then proceeded to describe her company's
line of ceramic fiber papers, their characteristics and cost range, claiming
Carborundum's paper line is economically competitive with asbestos paper.
Ms. Rudzinski inquired if any representatives of aramid or ceramic
paper manufacturers were present. Carol Mansfield (from Carborundum) indicated
that she and a representative of Babcock and Wilcox were present.
Mr. H.B. Kinsley added that James River Paper Company also makes a line
of ceramic papers.
Ms. Rudzinski next directed questioning to what in the way of performance
characteristics is lacking in substitutes.
Mr. Beto, GAF, stated that (for flooring) his company knows of no direct
asbestos substitute which is an economical, high performance, fire resistant,
noncombustible material. Mr. Beto went on to say that there is no single
substance (listed on the summary handout of substitutes) that does not have
some deficiency when compared to asbestos. Also, when one looks at the
economics, there is no good replacement.
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Mr. Beto, in response to a question about GAF's ability to find suitable
substitutes, stated that his firm is spending hundreds of thousands of dollars
trying to find substitutes.
Ms. Rudzinski asked about the cost differential between fiberglass-
containing and asbestos-containing products. Mr. Waldman of International
Paper Company said that the question cannot be answered directly because of
price differences between grades of asbestos.
Mr. Kinsley of the James River Paper Company stated that Hercules has
been working on their lexar fibers and that they presented a paper on the
process within the past year.
Ms. Rudzinski asked if there are any applications (for paper products as
well as for roofing products/coatings) for which there are no acceptable
substitutes.
George Odean of DuPont responded that in the line of specialty papers,
there is no direct substitute for asbestos membranes in certain electrolytic
cells. DuPont manufactures a line of asbestos-free membranes, Nafion, for
some elctrolytic diaphragms but it is not a direct substitute for the cells
that now use the asbestos membrane. In order to use the Nafion membrane,
the existing cells have to be replaced.
A representative of the Chloralkali Institute stated that the substitute
represents companies which manufacture Coroden® and that 75 percent of the
use is for diaphragm cells. He stated that asbestos is used with the dia-
phragm material and that there are no substitute membrane cells.
An estimate of 2 billion dollars was given for the conversion from
asbestos to substitute material in the chloralkali industry.
In response to a question about what type of properties would be required
for a suitable substitute for the asbestos membrane cell, the Chloralkali
Institute representative stated that he did not want to address that at the
present time.
Mr. Edmond Berrigan of DuPont Industrial Fibers Division stated that he
wanted to describe fibrous asbestos replacements which DuPont is developing
called Kevlar® and Nomex® They are continuous filament aramid fibers. The
fiber is used as reinforcing material for a number of applications, especially
for paper uses. It is economically competitive at a cost of $3.75 per pound
for the pulp. Like asbestos, fibrous material has desirable characteristics
such as high tensile strength. The fibrous pulp material has releasable
fibrils with aspect ratios in the respirable size range. Mr. Berrigan went on
to say that this fibrous material is well suited for applications like paper
because it is made by paper-making processes. However, the material can also
be used for other products such as beater-add gaskets or friction paper. Be-
cause the cost is high by asbestos standards, Kevlar® pulp is obviously not a
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direct substitute for all asbestos in paper products; however, it can replace
a small quantity of asbestos. Also, there are some applications, such as for
gaskets and friction paper, where it is economically feasible to use higher
priced fiber like the Kevlar® pulp.
In response to further questioning, Mr. Berrigan indicated that there are
definitely fibrils of inhalable size that can be released from the Kevlar® pulp,
but that it is very difficult to get the fibrils out of the material. The
exact number of fibrils that are releasable is not known, but it is a very
small percentage of the total. However, DuPont has addressed the problem of
the inhalation toxicity of aramid fibers. A paper presenting preliminary
results of an inhalation study will be given in the Health Effects Session.
To date, there is no evidence that DuPont should not continue to develop
production of these aramid fibrous materials.
Vance McCarthy (a reporter with a Mineral publication) brought up the
question about what guarantee is there that people who invest in research for
asbestos substitutes would not have to replace the substitutes later on after
they are tested.
Members of the panel asked that questions associated with health effects
of substitutes be deferred to the Health Effects Sessions.
Mr. Stimola asked that the group address a second question; what fibrous
product substitutes exist in the protective coating product field? In the
category of protective coatings, Mr. Stimola indicated that his firm knows of
no effective substitutes for asbestos even if they disregard economic con-
siderations. Although their firm is familiar with many products offered as
asbestos substitutes, in their opinion the substitutes do not work as well
as asbestos.
Jim Palmer, MiniFibers, stated that his company has a high density
polyethylene fibrous coating formulation that he has been working with for
about three years.
There are about 16 formulations for protective coatings, rib coatings,
etc. The fiber itself is called the "130380" and is economically competitive
with asbestos.
In response to a question about the material's degradation by mildew,
etc., Mr. Palmer responded that he was not too familiar with that aspect of
the product, but that he would give the questionner some literature.
Another participant (unidentified) stated that he would be speaking for
the roofing industry concerning substitutes for asbestos fiber. He
indicated that his firm has worked with MiniFiber's product and does not find
it to be a viable substitute for asbestos regardless of cost.
In response to Ms. Rudzinski's question as to what reason his firm finds
that the MiniFiber product is not an acceptable substitute, the unidentified
participant stated, for one thing, they could not keep it from settling. Also
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they had found it to be a fiber that burns and does not provide body to the
coating material.
A question was addressed to the chair about what EPA and the Office of
Toxic Substances thinks of synthetic organic fibers. The question about fiber
size was deferred to the Health Effects sessions. Participants were asked to
submit any weathering data that might be available.
The same participant raised doubts about synthetic fibrous coating
materials stating that the use of toxic fungicides compounds the (possible
health) problem. The staff invited the participant to submit any data he
might have on fungicides'"wear, etc.
Philip Battoli, GAP, stated that his company has been making roof coatings
for 90 years. Mr. Battoli stated that unfortunately there are now no
alternatives for asbestos for reasons already discussed.
Mr. Battoli stated he was not convinced that polyethylene or polypropylene
fiber is suitable for an outdoor environment. For example, in such
applications as flashing cement, a vital part of the roofing structure, these
organic fibers might not be able to withstand ultraviolet light, temperature
and other forces of nature as well as asbestos fiber could. Mr. Battoli went
on to say that shelf stability of alternates is not as good as that of
asbestos. There are also problems of premature failure and lack of proper
reinforcement. So, if there is an alternate, GAF has not yet found it.
Also, GAF has not found suitable alternates for certain types of gaskets.
Ceramic fibers may be useful in certain types of gaskets, but not for all.
Head gaskets, for example, have different performance requirements than
exhaust gaskets. Alternates for asbestos are being tested, but there is no
assurance of long term performance. If a firm converts a tractor or pit
asbestos gasket to an alternative asbestos substitute gasket, long term per-
formance data are needed.
Next was a discussion between Dave Bailie, Koppers, Inc., and another
participant about the use of one-ply asbestos-free membrane material for
repair or replacement of existing roofing coating.
Ms. Rudzinski next asked if there were representatives of other paper
products present — pipe wrap, millboard, etc., who would like to address some
of their substitutes and problems.
Ms. Mansfield of Carborundum stated that her firm has an array of mill-
boards, some of which are made with inorganic fibers and some of which are
made with organic fibers. In response to the question if Carborundum's
millboard products will substitute for all asbestos millboard applications,
Ms. Mansfield indicated "no", that she did not think anyone had a product
that will substitute in all cases.
It is very difficult to compare prices of substitute materials with
asbestos products, stated Ms. Mansfield. For paper, there are several grades,
as well as low and high temperature paper lines. As for millboard, there
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should be no equipment conversion costs, since Carborundum carries the same
sizes as the asbestos board now available.
Ms. Rudzinski asked if there were paper products other than for certain
gaskets and the flooring already discussed for which there are no known
substitutes.
Mr. Kinsley of the James River Paper Company stated that in the ten years
since the company has been incorporated it has not made any asbestos-based
products and has been looking for opportunities for non-asbestos products.
However, there are areas where there do not appear to be viable or economical
substitutes. Beverage filtration is certainly one of those areas.
A representative of Munson Products stated there are also roof coatings
substitutes which will require equipment changes and very substantial capital
expenditures.
Ms. Rudzinski next asked about substitute material durability.
In response, a participant indicated that where organic fibers are used
as substitutes, they degrade whereas asbestos does not. So there is no compar-
ability as far as durability with these types of substitutes. With synthetic
coating materials, one has to use a germicide or fungicide to keep rotting
from taking place. There is not yet enough experience with use of substitute
materials to be able to determine how comparable they are with asbestos-based
coatings.
The James River Paper Company representative H.B. Kinsley described
some performance problems with a specialty paper their firm is trying to
develop. With substitutes such as inorganic fibers, there can be problems
with the crush test and with creep resistance. Also, even if the higher-
melting temperature organic fibers do not creep, they probably crush. There
is a need for resiliency and high temperature resistance.
Further discussion of the performance problems of substitutes followed.
One participant said that roofing systems being installed today are
based on European technology. But durability of roofing systems in Europe
really cannot be used for comparison of durability of roofing in the United
States. Asbestos roofing systems have proven durability. Non-asbestos
systems have not been out there under all services, conditions, and applications
long enough for durability evaluations. Also, accelerated exposure/durability
testing cannot be directly interpreted. It is like an engine running at idle
speed. One cannot say, based on that, what the engine's performance will be
at high speed.
Glenn Simpson of CPSC inquired about earlier references made to the fire
retardancy aspects of asbestos in roofing mastic. Mr. Simpson stated that
references had been made earlier implying that a roofing mastic substitute
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(for asbestos) would not be suitable because it was flammable. But, Mr.
Simpson's question was whether the entire mastic mixture was flammable,
whether or not it contained asbestos.
A participant replied that claims of fire retardance of asbestos in
roofing coatings were not made, rather, the comments relative to roofing
coatings were made criticizing their organic fibers which degrade on weathering,
and their tendency to mildew, which degrades the whole product.
Asbestos fiber in an organic vehicle in the coating does degrade. The
speaker stated that his firm's organic fibers placed in that same organic
vehicle no longer contribute to the weatherability of the coating. In fact,
if the coating and fiber is mildew resistant, it detracts from the weather-
ability of the coating.
Another participant stated that the use of asbestos in asphalt does pro-
vide a great measure of fire resistance. A discussion of the characteristics
of asbestos-based asphalt follows in which the speaker reiterated that
asbestos-filled asphalt coatings are weather and fire resistant.
Ray Lawson of Southwest Petrochemical Division, Whites Chemical Company
stated there is a difference between resistance and retardance. Lawson
recited the military specifications for automotive undercoating on vehicle
undercoating. For an asbestos-containing asphalt coating placed in a flame,
it has to extinguish itself within a specified period of time (20 seconds
or so) after the flame has been removed. With an asbestos-containing coating,
the flame will estinguish itself. With synthetic or organic fibers, the flame
will continue burning. Mr. Lawson said that is resistance, not retardance
and there is a difference.
Ms. Spadafor asked questions about tests for substitutes — were there
observed differences in energy requirements for processing substitutes
versus asbestos products? Ms. Rudzinski added a question about whether
observed differences in energy requirements would be a controlling factor in
a decision to go with either one or the other.
Sam Elwood of H.B. Filler stated that for most of the substitutes his
firm has looked at, it takes a lot more energy to try to get products of
uniform consistency. When one is running a 125 hp motor 20 to 30 minutes
longer (even up to 1-1/2 hours longer) to get a uniform mixture, considerably
more energy is being used than when asbestos is being used. On energy con-
sumption, this is almost economically unfeasible.
A few other comments were made concerning the differences in energy
requirement between substitutes and asbestos-based products.
Since there was no response to Ms. Rudzinski's question if there were
any other points or questions to discuss, the meeting adjourned.
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SUMMARY OF THE ROUNDTABLE DISCUSSION ON
SUBSTITUTES FOR ASBESTOS TEXTILES
PANEL MEMBERS
Alan Carpien — (Moderator), EPA, Office of General Counsel
Bob Liss — EPA, Office of Pesticides and Toxic Substances
Sam Manfer — Carborundum Company
Dave Mayer — EPA, Office of Pesticides and Toxic Substances
Alan Carpien suggested that the group center its discussion on the tech-
nical performance of substitutes, and their lifecycle costs. He also
suggested that Sam Manfer of the Carborundum Company lead the discussion.
Mr. Manfer invited the group to bring up information on a variety of substitute
areas, since his expertise involved ceramic fibers.
Rick Hettich of Amatex pointed out the distinction between fire re-
sistent and flame resistent textiles. Fire resistent means that the textile
will burn when a flame is applied, but will self-extinguish when the flame is
removed. Manfer pointed out that there are different forms of ceramic
materials. Some are flame resistent, while others are fire resistent. He
said that they will remain inert in either case.
Phil Wagner of DuPont added that while Aramids are self-extinguishing,
flammability may be relatively unimportant. Sometimes whether or not a
textile is a good thermal barrier is the only important criteria.
Mr. Kennedy of Raybestos stated that chemical resistance was important
in the manufacture of chlorine. He said that many different fiber types had
been tried, but that no appropriate substitute had been found. Mr. Manfer
added that other chemicals needed to be tested.
Sam Manfer wanted to get back to the question of fire resistance. He
asked the group whether the leached silica fibers were effective above 1000°F.
Al Weiner of the Navy Department said that the terms self-extinguishing and
non-burning were not meaningful. He stated that some sort of standard test
was needed. Manfer asked whether these specifications were indicative of
the applications. Weiner stated that the CG test has been used to try to
indicate this, since no weight loss is the ultimate test of fire resistance.
Joe Sonatol of Pittsburg Corning suggested that the group center on
specific product applications. By generalizing, many cases in which fire
resistance is utmeeded would be discussed. It was decided that the list of
applications in question 1 of the agenda should be looked at.
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The first item was welding curtains. Bal Dixit of Newtex added that the
type of asbestos fabric must be specified. Commercial asbestos with 30 percent
rayon may burn under certain conditions.
Bob Liss asked whether there were specifications for welding curtains. Mr.
Manfer replied that welding blankets have specifications, but that they may
be made from a variety of materials including PVC, rubber, etc. Some of
these materials have been known to off-gas and produce cyanide. Lyle Cohen
of Magid Glove Company stated that specifications are up to the manufacturer.
Alan Carpien asked whether there were reasons for using one material over
another. Mr. Manfer responded that curtains were an open area, in that user
preference is important. Welding blankets must withstand molten metal
puddling. Asbestos has been the only material thus far to pass the military
specifications. Mr. Weiner disagreed, and stated that high temperature silica
products are actually better than asbestos, have a higher temperature
capability and, depending on abuse, are as durable as asbestos.
The next product line discussed was welding blankets. Mr. Manfer stated
that leached silica is effective, and asked whether any other materials were
known to be effective. Mr. Dixit added that there are many non-welding appli-
cations for blankets such as covering machinery. Artie Bower of Gentex
stated that Preox, Celiox Fiber is effective against molten metal splash.
The cost of this material is $18-20/yard. It is generally effective in
uses where there are short exposures to high temperatures, but not in long
term, high temperature exposures.
Don Johnson of 3M noted that Nextel (a 3M product) when used as a hybrid
has not passed the military tests. It was suggested that the group focus
on a discussion of the cost-effectiveness and end-use specific considerations
of various fibers. Alan Carpien then discussed the requirements necessary
for a finding on "unreasonable risk" which EPA must support for each regula-
tion of a toxic substance.
Bob Cordick of Araco stated that fiberglass is acceptable in textile
applications where temperatures are 1000°F, up to 1800°F. It begins to
weaken at temperatures of 700°F, but has been used for applications in which
asbestos has not been moved. Silica cloth is also available for uses in
temperature ranges of 2000-2300°F. The cost is dependent directly upon
application. In some applications, it lasts six times as long as asbestos,
yet costs only twice as much as asbestos. There may be additional economies
involved through energy savings. In steel mills, high temperature textile
applications have cut energy costs drastically. Al Weiner pointed out that
several other parameters reduce the temperatures that textiles can meet.
Steam, vibration and, refractory temperatures, all effect the durability of
textiles.
Phil Wagner of DuPont stated that Nomex, Kevlar, and Teflon were all
asbestos replacements. Their costs range from $5-$32 per pound versus
approximately $.25 per pound for asbestos. These materials may be spun of
conventional equipment. When Dupont markets these products, they use a
system called the value-use system. This basically involved defining the
216
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exact use for a customer's product. Producing expensive substitutes can be cost
effective if they are produced quickly, and in bulk. Also, if the materials are
light weight (a small amount goes a long way), abrasion resistant, and have
increased longevity over asbestos, they can be sold much easier. Also, these
materials are rarely used alone but generally as hybrids. Kevlar and Nomex
are aramids (nylons), they are high temperature resistant, flame resistant,
and have no known melting points. They will off-gas at 800°F, depending on
time and atmosphere.
Bal Dixit said that their main product, Zetex, is a fiberglass textile.
A representative from Celanese, Bill Timmons, stated that they produce
"Preox". This is a thermally stabilized polyacrylonitrile. It carbonizes
at high temperatures, is not electrically conductive, and has good water
absorption properties. Additionally it is quite flexible, but emits cyanide
gas at 800°F. It will not support combustion in air. Alan Carpien asked for
submission of additional information on this product.
Sam Manfer stated that while asbestos is replaceable, technical material
on its substitutes provides little information on the application of sub-
stitutes. Alan Carpien responded that the Agency would like to get the best
data possible for decision making. He called for submission of all substitute
data which could aid the Agency in this endeavor.
Lyle Cohen of Magid Glove Company criticized all gloves. He stated that
asbestos gloves are used only where they are necessary. They are big and
clumsy. Replacements for asbestos gloves are not good either. Kevlar
failed, and Zetex is too expensive. Al Weiner stated that gloves using a
Kevlar and leather combination have been used successfully. Bill Myers of
Amatex cited a study by Nottick Laboratories on safety clothing which showed
that Kevlar did not hold up in some cases. Mike Wright of the United Steel
Workers Union stated that steel workers were satisfied with the replacement
gloves. He noted that in many cases a specific process should be examined.
Often workers could be less involved in high temperature processing. Sam
Manfer questioned the use of other fibers in gloves. Bal Dixit said that
other fibers could be used if time was allotted to develop substitute products.
Alan Carpien asked how long this development process would take. Sam Manfer
replied that time was directly proportional to the pressure industry felt
to develop substitutes.
Kathleen Gaillner of Koppers Company said that no substitute had been
found for coke oven door jambs. They require materials which are flexible
and can withstand temperatures of 2000°F. She added that the aluminum
industry had also been looking for substitutes, but had not located them.
Mike Wright suggested that if a company let it be known that they required
specifications for an end-use, a substitute could be found. A representative
of Dupont responded that simply looking at end-use may not be enough, because
often the product and/or the application change. He estimated a time frame
of about 3 years to develop a substitute for an application of this sort.
217
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Al Weiner stated that the Navy had decided to use non-asbestos products
where possible. Jack Reed of Amatex said that his company had a textile
product which is rayon treated with phosphazine. It decomposes at tempera-
tures of 400-500°F. It will burn, but extinguishes when the flame is
removed. It costs approximately $3.50 per pound.
For electrical insulation, Bal Dixit reported that Zetex was adequate for
thermal and electrical insulation. It has a lower (less than one-half of
the time) thermal conductivity than asbestos. Dupont produces Nomex which
is limited to 220°C.
218
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SUMMARY OP THE ROUNDTABLE DISCUSSION ON SUBSTITUTES FOR
ASBESTOS-CEMENT SHEET
PANEL MEMBERS
Dale Ray — (Moderator), CPSC
David Cogley — GCA Corporation
Elliot Foutes — CPSC
Hope Pillsbury — EPA, Office of Pesticides and Toxic Substances
Dale Ray of CPSC and Hope Pillsbury of EPA opened the discussion with a
brief background description of the purpose of the roundtable discussions.
David Cogley of GCA Corporation also invited comments on GCA's Summary Report
on Substitutes for Asbestos, which had been distributed to participants. The
following is a synopsis of the discussion on various points.
Dennis Kelleher and Sid Speil of Johns-Manville* had comments on the
Summary Report on Substitutes. They asked what level of the supply chain
the cost figures were for, in Tables 10 and 11. They commented that the
figures were misleading and offered to supply the correct figures. John Jones
of Cem-FIL and Frank Fekete of GRC Corporation also offered to supply
corrections to the figures.
Michael Vaudreuil of ALCOA wanted information about asbestos-free
marionite. He commented that ALCOA has found that asbestos-free marionite
was a feasible substitute for asbestos-containing marionite, except in the
largest diameter mold sizes, for which the asbestos-free product degraded
more rapidly. Representatives from Johns-Manville asserted that all non-
asbestos products degrade more rapidly than substitutes.
A.R. Frederick of General Electric commented that his company uses
A/C sheet, in thicknesses of V-2", for electrical boards, circuit
breakers, etc. A/C sheet is used because it is strong, and has high
electrical and heat resistance.
Representatives from Johns-Manville said that flat A/C sheet is used
in schools and residential buildings. They also said that fiberglass-
reinforced plastic, in corrugated sheet form, can be used in cooling towers.
They said that glass-reinforced concrete (GRC) is less wind-resistant than
A/C sheet.
John Jones of Cem-FIL described GRC. It contains glass fibers from
y-lJs" long. They are uniformly distributed in the matrix. A variety of
fillers can be used in this product. Typical ingredients are Portland
cement, marble dust, and glass fiber. GRC can be used outside for siding
and other weather-resistant uses.
*
Hereafter called representatives from Johns-Manville.
219
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Representatives from Johns-Manville asked Frank Fekete (of GRC
Products) and John Jones to supply design figures and ultimates for GRC.
John Jones replied that GRC can be used in place of most applications of
A/C sheet. GRC's machining characteristics are not as good as those of A/C
sheet; although GRC can be drilled and bolted it tends to chip. Its heat
resistance is not as good as that of transite, which is produced by Johns-
Manville. Portland cement which is used in their standard GRC products,
dehydrates at temperatures higher than 500°-600°. Now Cem-FIL is working
with high--"luminum cement (refractory cement) . It has been tested to 1000°F.
Transite is good at 600°F. John Jones also noted that their Portland cement
product has only 5 percent fiber, as compared to A/C sheet which has 12-
18 percent fiber.
Representatives from Johns-Manville asked John Jones about the strength-
aging effect^ They stated that they had information that glass in cement
deteriorates after 5 years. They asked if this had improved?
John Jones replied that his company has field data showing the
durability of GRC over 12 years. It starts out with a strength of 4,000 psi,
and stabilizes after 4-5 years at 2,000 psi.
Representatives from Johns-Manville said they had information that the
limit of proportionality for GRC is about 1200 psi. John Jones replied that
GRC has been tested in the tropics, in temperate zones, and in the desert,
by Pilkington Brothers in conjunction with the British government. The
original GRC showed that the 28-day strength was 4,000 psi and the strength
after 4-5 years was 2,000 psi. The improved GRC now has a long term strength
of 3,000 psi. Representatives from Johns Manville said that GRC weakened with
time down to the strength of unreinforced cement. John Jones disagreed with
the above statement.
Representatives from Johns-Manville commented that the limit of
proportionality of A/C sheet goes up with age. They also commented that the
design limit for GRC was 870 psi but that A/C sheet was about 1000 psi.
John Jones of Cem-FIL reported that Fiberglass-reinforced plastic is
used in corrugated form in cooling towers. It is also used as a skylight in
industrial buildings. It is stronger than A/C sheet, but flexes more.
John Jones of Cem-FIL noted that there are 2 manufacturers of GRC sheet.
Thirty companies in the United States make other types of GRC products, but many
of them, such as some of those manufactured for architectural uses, are not
replacements for A/C sheet.
Representatives from Johns-Manville described cement-wood board. It is a
cement product with a high wood content. Its high cellulose content absorbs
moisture, thus the sheet tends to expand and contract a lot. Similar
problems with expansion have been experienced with cellulosic roofing felt
and other products with high organic content.
220
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Cement-wood board is used for interior applications because it is light
and flexible. It is similar to masonite except that it has a Portland
cement binder rather than a resin binder. It is used in roof underlayment
in countries with low supplies of wood. It has weathering characteristics
similar to those of marine plywood. They also commented that cement-wood
board, when used as fill in cooling towers, would ruin the efficiency of the
cooling towers if the material warped. Cement-wood board used in one cooling
tower in the northwest United States is now being replaced with A/C sheet.
John Jones of Cem-FIL has supplied GRC for use as cooling tower fill, however
not the GRC product which is made of Portland cement.
David Cogley asked if A/C sheet is prevalent in ovens, safes, and
heaters? Has GRC been used behind wood stoves?
John Jones of Cem-FIL commented that GRC has been used around furnaces;
though not necessarily the GRC made with Portland cement. This GRC is made
with a refractory cement which has a light-weight filler, so that it does not
explode with heat. The GRC made with Portland cement may explode if exposed
to a rapid change in temperature. A/C sheet may also explode if it is not
porous enough. GRC can be installed behind stoves if it is U.L. rated.
Concrete Design Specialties in East St. Paul, Minneapolis makes GRC for use
behind wood stoves. Energy Research and Development Corporation makes
ceramic fiber board for the same use. One can buy it now through Johns-
Manville (Ceraboard), Carborundum, and other companies. The cost of these
substitutes is 2% times the price of asbestos-containing millboard.
Representatives from Johns-Manville stated that GRC cannot be used in
highly corrosive environments such as ceilings in paper mills, where there
is much moisture. John Jones of Cem-FIL asserted that in those cases it is
the cement that gives out. Representatives from Johns-Manville said that
metal reinforcement cannot be used in the above environments.
Dale Ray of CPSC asked if there are any applications for which we are
not close to an adequate substitute for A/C sheet? Hope Pillsbury added
that laboratory table tops might be an example of-such an application. John
Jones of Cem-FIL said that there may be no comparable non-asbestos product
for laboratory table tops. Slate exists but it is inordinately expensive.
Hope Pillsbury asked if any of the more expensive substitutes could
become cost effective with economies of scale.
»
Representatives from Johns-Manville replied that A/C sheet is better
than other products in terms of life cycle cost.
John Jones of Cem-FIL said that economies of scale with greater sales
of GRC should lower the price of this material, although not to the level of
A/C sheet, because glass fiber is more expensive than asbestos fiber. John
Jones expects that the price of GRC could decline to within 20 percent of the
price of A/C sheet. In Europe, a nonasbestos GRC sheet called Tak-board is
produced at the same price of A/C sheet, but Tak-board is an inferior material.
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Dale Ray of CPSC asked to what extent can existing capital equipment be
used to produce substitute materials or products?
Representatives from Johns-Manville said that in Europe they have looked
for substitutes for asbestos for 20 years. They also noted that existing
machines used to make A/C sheet require flexible fibers in order to work.
The representative from the Suzorite mica association said that people
are developing complex mixtures that can be run on existing machines. The
Hatscheck machine is used most often, but the Fourdrinier and Magnani
machines can also be used. The Magnani is used for corrugated board in
Denmark. He also said that mica runs quite well through the machines. It has
good drainage characteristics, therefore it has been able to substitute for
crocidolite and amosite.
The representative from the Suzorite Mica Association said that a law
has been passed in Japan requiring reduction of asbestos content in A/C sheet
to 5 percent down from 12 percent.
In Denmark and Sweden laws have been passed banning asbestos. Viable
substitutes have not been found for A/C sheet. Some work on a small scale
but there are reproducability problems on the large scale. Many contain
some asbestos.
Irv Huseby of General Electric said that his company is looking for a
substitute for transite in arc-shoot applications. The modulus of rupture
is 3,000-12,000 for that material. The substitute they are looking for
must have a modulus of rupture of 7,000 psl on a 2" stand. It must also
pass a 3-point bend test. A/C sheet can pass these tests. Someone asked
if they had tried wollastonite. Irv Huseby said that it acts like a
ceramic.
Lauren Choate of NYCO, a division of PMI asked what was the rupture
strength before the wollastonite broke.
John Jones said that there are international building standards for A/C
cement; spacing of supports, etc. You need freeze/thaw tests, hot/dry
tests, hot and humid tests, temperate, and monsoon tests, etc.
Lauren Choate said that wollastonite is used in Denmark. It is not
as good as asbestos. Use of asbestos will be banned after 5 years in
Denmark if there is a suitable substitute.
The representative from the Suzorite Mica Association said that 85 percent
of the roofs in Denmark are made with asbestos. In the war years asbestos
was not available so they used wood fiber. After 5-20 years the performance
of the wood fiber in the roofs was not as bad as expected. The expansion and
contraction on these roofs was quite large compared with that of asbestos-
containing roofs.
Barry Castleman, a consultant, listed patents which various companies had
on materials which could substitute for asbestos.
*
222
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Dale Ray asked to what extent, existing capital equipment can be
used to produce substitute materials or products?
The representative from the Suzorite Mica Association said that it costs
$4,000/week to try a new substitute material out on an asbestos-cement machine.
Full-scale tests are necessary because even a small-scale A/C sheet machine
does not give you the correct information. The total cost of the tests was
about $10,000 for one week. The equipment to do the job may be valued at
several million dollars.
John Jones of Cem-FIL said that GRC has been made on a Hatscheck machine
and a magnani machine. There can be problems because of glass' tendency
to flocculate. GRC was not developed as a replacement for A/C sheet. It
cost several million dollars to develop alkali-resistant glass. Just a
few percent of this money was directed at developing asbestos substitutes.
A lot more is applied to light-weight concrete substitution than to A/C sheet
substitution.
A representative from Carborundum said that development of ceramic fiber
board was not aimed at the asbestos-replacement market. Millions of dollars
were spent on research and development.
Frank Fekete of GRC Products said that the capital equipment to produce
GRC was brought to the United States from England. The equipment alone (not
including land or property) cost 1% million dollars.
Dale Ray asked if energy requirements would be changed substantially by
switching to production or use of the nonasbestos material? Representatives
from Johns-Manville said the ratio of energy use between producing PVC pipe
and A/C pipe was 4:1. They also commented that glass fibers take more energy
to make than do asbestos fibers. The representative from the Suzorite Mica
Association said that mica requires $1.50/ton.
David Cogley asked if the autoclaving and drying time for A/C sheet re-
quired a lot of energy?
A representative from Johns-Manville replied that the more autoclaving
time is used, the less drying time is required, and vice versa.
Barry Castleman, consultant, commented that Rafael Ramos Lacen has re-
ported that polyurethane sandwich panel is used in various housing projects in
Puerto Rico. It is used in interior and exterior walls. It is not covered
with an aluminum skin in Puerto Rico and in other developing countries.
The representative of the Suzorite Mica Association said that polyurethane
has extremely toxic by-products of combustion. If the cover is removed
metal would tend to protect it, but if the plaster wallboard protecting it
falls off, then urethane foam is exposed. This material is not a viable
alternative to A/C sheet because of the fire hazard.
223
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Irv Huseby of General Electric said that a fracture/toughness test was
needed such as a 3-point bend test or other similar stress test in order to
rate replacements for A/C sheet. These tests are done by ceramacists.
John Jones of Cem-FIL asked if those tests were of slow or impact loads?
Impact tests are run by Cem-FIL.
Irv Huseby of GE replied that impact tests are a good first start. Slow
fracture/toughness tests are also needed. At GE they have been able to re-
place about 10 percent of the uses of arc-shoots with a nonasbestos product.
Polyester-pressed molding would not take the temperatures.
Supradur makes roofing shingles and siding out of asbestos cement.
224
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SUMMARY OF THE ROUNDTABLE DISCUSSION ON
SUBSTITUTES FOR ASBESTOS-CEMENT PIPE
PANEL MEMBERS
Richard J. Guimond — (Moderator) EPA, Office of Pesticides and
Toxic Substances
Arlene Levin — GCA Corporation
Richard McAllister --- EPA, Office of Pesticides and Toxic
Substances
RANGE OF APPLICATIONS
Three types of asbestos-cement (A/C) pipe were identified: pressure pipe
for drinking water, non-pressure pipe for sewers, and square pipe for air
ducts.
It was mentioned that at one time A/C pipe was used for food pipes.
Rectangular-shaped A/C pipe, made only in Europe and used as air ducts,
were discussed. This pipe is very thick, and its diameter is wide; from 4"
to 36" if not wider. It is air cured. Round air duct pipe is also available.
ALTERNATIVE PRODUCTS
PVC, cement, clay, steel and iron were identified as substitutes for A/C
pipe. Mr. James Warden of the U.S. Water and Power Resources Services
commented that in a range of up to 24 inches A/C pipe is very competitive
with the substitutes, but above 24 inches the other pipes become competitive,
and above 42 inches A/C pipe is not competitive at all.
Concrete pipe containing glass fibers was discussed as a possible sub-
stitute for A/C pipe. Mr. Joseph Jackson, representing the A/C Pipe
Association, made the point that fiberglass, even the alkaline-resistant glass,
does not maintain its strength in alkaline environments over long periods of
time. The clay and glass silicates melt when autoclaved; therefore, fiber-
glass is an impractical substitute material.
The conclusion of this discussion was that substitutes for asbestos-
cement pipe are not available in the form of Substitute fibers, but rather,
are available only as alternative products such as concrete or steel. It was
225
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mentioned, though, that a company is developing a wire pipe fiber in which
about five of these fibers (each about an inch or an inch-and-a-half long) are
glued together by a soluble glue. The soluble glue dissolves when the fibers
are put into the cement, making it easier to handle. This is being tested for
concrete pressure-pipe applications. It was also thought that a German
company, named Eternit, was researching a new fiber that had the same
properties as asbestos.
Concrete is used for pressure-pipe applications up to 150 feet a head,
and diameters from 12 inches up to 132 inches. PVC, ductile iron,, concrete,
and steel are used for pressure pipe. Clay pipe is not used for pressure
applications. Someone asked whether any pipe that was used for pressure
applications could also be used in sewers. Someone replied that metal pipes
would not' be used in sewers because of the inversion process. It was
concluded that concrete, clay, fiberglass, and plastic pipe could be used
for non-pressure pipe. Someone said that plastic pipe had half of the
market, however, when challenged, revised his statement to conclude that
plastic pipe has a large share of the market.
Mr. Young Joe of Substitute Abrasion, mentioned a fiber containing 10-
15 percent carbon fibers and also glass fibers or ceramic fibers, for use
in pipes. Someone commented that they thought inclusion of carbon fiber
would increase the costs of the pipe so it would be no longer marketable,
but Mr. Joe said the fibers increased the cost of the pipe only slightly. He
commented that the cost of the carbon fiber was in the $6-8 range.
Mr. Barry Castleman listed some patented fibers such as a cotton-
reinforced center product made by GAF; a Japanese patent from Asahi Glass Company,
which is a reinforcing material for cement sheet, containing glass, cotton,
and silk; a sulphur aluminum used in cement; a resistant mineral from
Sweden; and a coated resistant glass fiber from Johns-Manville.
Someone commented that the materials listed were all fibers used to
fortify cement; these products are all cured naturally, therefore, they
contain a porcelain cement binder. The products are quite alkaline. The
commenter also said that when the matrix in these products is subjected to
a temperature in excess of 354 degrees Fahrenheit most of the materials
mentioned would dissolve. Also, many of these materials cannot be
processed on the same type of machinery that is used to make asbestos
products. A fiber will be commercially usable if it can be processed the
way A/C pipe is made, if it can be autoclaved and still maintain long term
strength and reinforcement to meet all of the American Water Works
Association specifications.
Pretention steel pipe up to 54 inches is the most economical pressure
pipe. A/C pipe is sold in diameters up to 42 inches.
General agreement was reached that there are substantial competitive
products to A/C pipe for all the ranges of pipes. There was also agree-
ment that no fiber is presently available that could substitute directly for
226
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asbestos fiber In A/C pipe, as it is presently manufactured and cured in the
United States.
Mr. James Warden from the U.S. Engineering and Research Center, U.S.
Department of the Interior, commented that most pipe they put in the ground
of a size 24 inches and less is A/C pipe regardless of the head. Above 24
inches and up to about 36 inches, the pretention steel pipe is quite
competitive, and above that range all the other types of pipe become
competitive. A cost-to-performance analysis is important in the selection
of a pipe. In a municipality, the operational and maintenance costs, or life
cycle costs are Important.
Equipment costs for'adapting an existing process to a new fiber must be
considered.
Installation costs will differ from pipe to pipe. A/C pipe is very
rigid in all sizes, facilitating its installation, whereas, ductile pipe
is non-rigid and therefore more costly to install in larger sizes.
A/C pipe imports are very low. There is a captive market for certain
specifications of pipe.
ENERGY UTILIZATION
Energy is utilized by substitutes in the physical product and in manu-
facturing. Various associations have calculated their own ratio's of energy
utilization, but these calculations may be biased. For example, A/C pipe
used 4 times more energy than PVC pipe; 2 times more than concrete pipe; and,
8 times more than cast iron pipe.
RESEARCH AND DEVELOPMENT
Linings and coatings for pipe are being Investigated to eliminate the
leaching of harmful substances from the pipe itself or the surrounding area
into whatever material is conveyed in the pipe. A/C-pipe does not corrode
externally but might corrode internally in aggressive water. TCE can leach
out into water. Sometimes coal-tar pitch, asphalt (petroleum-based) and
steel can be used as (external) coatings. A perfect lining has not been
found.
PRODUCT SPECIFICATIONS
There are no pipe specifications or generic standards. Pipes are made
to meet the criteria of the American Water Works Association (AWWA) or the
American Society for Testing and Materials (ASTM).
227
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PRODUCT AND SUBSTITUTE MATERIAL REVIEW SESSION
The purpose of the Product and Substitute Material Review Session was to
provide a forum in which any expert on a substitute for asbestos fiber or an
asbestos-containing product could present information about the substitute.
Those who were interested in participating in this session were sent guidelines
informing them what type of information they should supply. The following,
are the edited excerpts from information supplied to EPA, organized alphabeti-
cally by the name of the organization submitting the information. The data
presented are believed to be correct, but EPA cannot guarantee their accuracy.
It should also be understood that EPA and CPSC do not endorse any products.
229
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COMPANY NAME Amatex Corporation
1032 Stanbrldge St.
Norristown, Pa. 19401
PRODUCT NAME Nor-Fab and Thermoglass Industrial Textiles
APPLICATIONS
Nor-Fab
Yarns Cords
Roving Braided tubing and packing
Filler Twisted and braided ropes
Tapes Fabric
Thermoglass Textiles
Cloth applications
Lagging Flange and valve covers
Welding shields Spray shields
Fire blankets Stress relieving
Laminating Protection of flexaust hose in steel mills
Tape applications
Pipe, meter linea and hose wrapping
Oven door seals
Fabricating tadpole gasketing
Thermal insulation
Pipe hangers
Tubing applications
Protection of metal tubing, thermocouple leads, hose lines,
wire and cable
Stress relieving
Oven door seals and thermal insulation
Rope applications
Packing for furnace doors, boilers
Core tadpole tape
230
-------
Suitable for:
• Nor-Fab could replace Commercial Grade and Underwriters' Grade
asbestos material (75 to 80 percent asbestos content).
• Thermoglass could replace asbestos products from Commercial Grade
through AM grade (75 to 95 percent asbestos content) .
Situations substitute not adequate:
• Nor-Fab not suitable to replace high grades asbestos such as AA
and AAA grade materials.
• Thermoglass not suitable for temperatures above 1000°F.
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Nor-Fab
TYPICAL PROPERTIES
Color
Fiber Make-up
Mildew Resistance
Abrasion Resistance
Stretch Resistance
Flexibility
Workability
Heat Resistance
Color Change
Weight Loss
Strength Retention
Light Yellow
Non-asbestos
Excellent
Very Good
Very Good
Very Good
Excellent
Excellent to 650'F
Darkens at high
temperature
Very slight to 650'F
Excellent to 500°F
DATA—22PT7 CLOTH—within 10%
Breaking Load
(Travail,
Effect of High
Temperature
Weight Loss
Strength Retention
Specific Gravity
Soluble Chlorides
Ph
Corrosion & Chem-
ical Resistance
Electrical Resistance
ASTM D-257
Thermal Conductiv-
ity K—ASTM C-177
'Thermal Conductivity by
Guarded Hot Plate Method"
Total Conductance
Total Resistance Ft
Warp—185 Ibs.
_FIII—95lbs. .
Does not melt, de-
composes between
700'F and SWF
2% at 660'F
54%at660'F
1.51
Less than WOppm
7.2
In compliance with
MIL-I-24244A
3.0x70"
(Btu-ln)
(Hr'FP* ' F)
(Av. Temp 77.73'F)
K= 0.560
C = 8.08
Ft = 0.124
CHEMICAL RESISTANCE-NOR-FAB 22PT7
CHEMICAL
ACIDS
Hydrochloric
Nitric
Sulluric
ALKALIS
Ammonium
Hydroxide
Sodium
Hydroxide
-S CONCEN-
- IRAIION
35
70
70
57
50
TEMP
°f °C
70 21
70 21
70 21
70 21
7021
TIME
HRS
1
1
1
1
1
EFFECT ON BREAKING STRENGTH
£
II
I/I
Wt
X
X
*!
i
>
!!
II
(-* *
II
•*z
X
si
If
OO
Because we cannot anticipate or control the many different conditions under which this information and
our products may be used, we do not guarantee the applicability or the accuracy ol this information or
the suitability of our products in any specific application Users ol our products should make their own
tests to determine the suilabilily of each such product for their particular purpose; The products dis-
cussed are sold without" warranty, either express oT implied, and buyer assumes all responsibility for
loss or damage arising from the handling and use ol our products, whether done in accordance with
directions or not Also, statements concerning the possible use of our products are not intended as
recommendations to. use our products m the infringement of any patent
231
-------
Thermoglass Textiles
NONFLAMMABLE: THERMOGLASS products will not burn or smolder.
HIGH HEAT RESISTANCE: May be used at surface temperatures ranging
from 120°F to 1000°F. Retains 50 percent of tensile strength at
700°F, and as much as 25 percent at 1000°F.
EXCELLENT DIMENSIONAL STABILITY: Will not stretch or shrink. No
more than 3 percent elongation under maximum stress. Retains
stability even at high temperatures.
HIGH TENSILE STRENGTH: Highest strength-to-weight ratio of any
industrial textile product.
CHEMICAL RESISTANCE: Inorganic THERMOGLASS is highly resistant to
most chemicals. Will not rot or mildew.
EXCELLENT ELECTRICAL PROPERTIES: High dielectric strength and low
constants.
GREATER FLEXIBILITY: The very fine filaments used in making
THERMOGLASS give it a high degree of flexibility.
FINISHES: THERMOGLASS textiles can be treated with special
finishes to meet specific requirements. These finishes include:
heat treatment to improve cutting and sewing, waterproof finish,
rewet finish, pre-applied adhesive. It can also be supplied with
aluminum foil, Neoprene or vinyl finish.
Performance Standards
MEETS U.S. COAST GUARD REQUIREMENTS: THERMOGLASS conforms to U.S.
Coast Guard requirements for Incombustible Materials, subpart
164.009.
APPLICABLE SPECIFICATIONS: Amatex THERMOGLASS products can be
manufactured to meet U.S. Government specification MIL-C-20079
and other customer specifications, as required. For insulation
materials with special corrosion and chloride requirements,
THERMOGLASS products can be supplied in conformance to MIL-I-24244.
COSTS IN PRODUCTION
Costs of process changes; No change required by the users to switch
from asbestos to a substitute.
Production costs compared; Same as asbestos.
COSTS IN USE
» Information not supplied.
232
-------
In the case of a government restriction on asbestos, increased
production is not expected to reduce costs.
LIFETIME COSTS OF USING PRODUCTS
Just about equal.
HEALTH INFORMATION
Thertnoglass; To the best of our knowledge no health hazards are known
except possible skin and eye irritation.
Nor-Fab 400 Series; Aramid fibers as used for these products are
supplied by E. I. DuPont De Nemours & Co. and have been tested by them
for toxicity by skin contact tests on animals and humans. No toxic
reactions have been observed. No reports of skin irritation or other
health hazards associated with this fiber during extensive market
development activity.
BIBLIOGRAPHIC INFORMATION
Thermoglass:
Owens Corning Fiberglass
Pittsburgh Plate Glass
Nor-Fab
E. I. DuPont De Nemours
Owens Corning Fiberglass
Pittsburgh Plate Glass
Manufacturer's Contact;
Mr. W. Maaskant
Amatex Corporation
1032 Stanbridge St.
Norristown, Pa. 19401
233
-------
COMPANY NAME
The Andersons
Cob Division
•P.O. Box 119
Maumee, OH 43537
®
PRODUCT NAME Grit-0'Cobs®, Mix-0'Cobs™, Lite-R-Cobs
APPLICATIONS
Grit-0'Cobs, Mix-0'Cobs and Lite-R-Cobs corncob products could substitute
for asbestos, all or in part, in the following applications.
Lost circulation material for oil drilling
Brake shoe component
Asphalt coatings and sealants
Bituminous concrete
Filler for plastics and flooring
Filler in paper products
Component in gasket material
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Mix-0'Cobs Lite-R-Cobs
Property
Elemental Analysis: Carbon
Hydrogen
Nitrogen
Oxygen
Phosphorous
Sulfur
Potassium
Sodium
Magnesium
Silicon
Iron
Calcium
Aluminum
Barium
Chromium
Copper
Lead
Manganese
Nickel
Vanadium
Zinc
Selenium
Cobalt
Grit-0'Cobs
43.5%
7.9%
0.21%
48.4%
0.021%
0.013%
0.93%
0.14%
0.11%
0.089%
0.013%
0.011%
0.0053%
<0.0001%
<0.0001%
<0.0001%
<0.0001%
<0.0001%
<0.0001%
<0.0001%
<0.0001%
<5 ppb
0.00001%
44.2%
7.4%
0.42%
47.9%
0.05%
0.12%
0.90%
0.11%
0.10%
0.090%
0.015%
0.04%
0.0054%
<0.0001%
<0.0001%
0.0002%
<0.0001%
0.0002%
<0.0001%
<0.0001%
0.0001%
<5 ppb
0.00001%
44.8%
6.9%
0.62%
47.4%
0.07%
0.22%
0.87%
0.08%
0.09%
0.090%
0.017%
0.06%
0.0054%
<0.0001%
<0.0001%
0.0003%
<0.0001%
0.0003%
<0.0001%
<0.0001%
0.0002%
<5 ppb
0.00001%
234
-------
SELECTED PROPERTIES AND DESCRIPTION OF PRODUCTS
Grit-0'Cobs are manufactured from the woody ring of corncobs, Llte-R-Cobs
are manufactured from the coarse chaff, fine chaff and pith of corncobs, and
Mix-O'Cobs are produced by blending Grit-0'Cobs and Lite-R-Cobs in a ratio
suitable for various end uses. The properties presented herein for Mix-O'Cobs
assume a 1:1 blend of Grit-0'Cobs and Lite-R-Cobs. Selected properties of
the subject materials are listed below. For additional information on prop-
erties, uses and methods utilized to obtain test data, please refer to
"Physical Properties, Chemical Properties and Uses of the Andersons' Corncob
Products."
TGA
Property
Oil Absorption
Water Absorption
Bulk Density
Specific Gravity
Solubility in
Acetone
Solubility in
Ethyl Alcohol
Solubility in
Alcohol-Benzene
Solubility in
Benzene
Solubility in Ether
Solubility in
Isopropyl Alcohol
Solubility in 1%
Potassium
Hydroxide
Solubility in 10%
Sulfuric Acid
pH (bulk)
pH (surface)
Grit-0'Cobs Mix-O'Cobs Lite-R-Cobs
100%
133%
28 lb/ft3
1.3%
2.5%
5.6%
9.5%
0.4%
0.3%
0.42%
18.6%
2.5%
4.9%
7.4%
300%
430%
20 lb/ft3
1.5%
2.3%
4.8%
8.2%
0.4%
0.9%
0.36%
18.6%
2.5%
4.9%
7.4%
500%
727%
12 lb/ft3
1.6%
2.1%
4.0%
6.8%
0.3%
1.4%
0.29%
18.5%
2.4%
4.9%
7.4%
The Thermogravimetric analysis of the Grit-0'Cobs is shown on the next
page. This should be of assistance in defining the temperature limitations
of corncob products.
235
-------
THERMOGRAVIMETRIC ANALYSIS
Ni
U>
Temperature, °C
1000
-------
RESEARCH AND DEVELOPMENT
The greatest need for research and development in utilizing corncob
products as an asbestos replacement is in the end product use area. This
Includes the areas of end product formulation and end product performance.
ECONOMIC INFORMATION
Costs in Production;
Where a corncob product can be directly substituted for asbestos, there
would be little or no cost associated with process changes. Where a corncob
product is substituted in part for asbestos, the economics are more complex
because the corncob product is only one of the materials involved in the
substitution. The costs associated with the latter substitution would be
expected to vary from product to product and from formulation to formulation.
Costs in Use;
The cost of Grit-0'Cobs, Mix-0'Cobs and Lite-R-Cobs products vary from
roughly 5 to 10 cents per pound depending on the grade, the quantity purchased
and whether it is purchased in bulk or bags.
HEALTH INFORMATION
A product safety and regulatory compliance bulletin is enclosed. This
contains health information on corncob products.
BIBLIOGRAPHIC INFORMATION
Pages 357 through 385 of "Physical Properties, Chemical Properties and
Uses of the Andersons Corncob Products" give bibliographic information on
corncob products. A copy of this publication can be obtained from the manu-
facturers' contact.
MANUFACTURERS' CONTACT
Dr. Kevin M. Foley should be contacted for technical information on
corncob products. David Vander Hooven should be contacted for information
on price and availability. The address and phone number of these people is
given below.
The Andersons
P.O. Box 119
Maumee, OH 43537
(419) 893-5050
237
-------
APPENDIX A
PRODUCT SAFETY & REGULATORY COMPLIANCE INFORMATION
BULLETIN FOR CORNCOB PRODUCTS
(1) Chemical Composition of Corncob Products
Grit-0'Cobs® Lite-R-Cobs®
Corncobs granules granules
Cellulose 41% 47% 35%
Hemicellulose 36 37 37
Pentose fraction 35 37 35
Xylan fraction 30 32 30
Lignin 67 5
Moisture 10 7 6
Protein 2.5 1.4 4.4
Fat 0.5 0.2 0.9
Ash 1.5 1.2 1.6
pH (bulk) 5 (determined in 1 to 4 (w/w) ratio of Grit-0'Cobs granules
to Water (dist.))
(2) Pesticide Residue Information
A typical analysis of Grit-0'Cobs contained less than 0.02 parts per
million of aldrin, gamma-BCH, BHC, chlordane, DDD, DDE, DDT, diazinon,
dieldrin, disulfoton, endrin, ethion, heptachlor, heptachlorepoxide, lindane,
malathion, methyl parathion, parathion, thimet, thiodan, trithion.
(3) Fire and Explosion Properties
Property Test Method
Ignition Temperature
(Grit-0'Cobs Granules) 401°F (ASTM D-1929-68)
Fire Point - Open Cup (Grit-0'Cobs Granules) 388°F (ASTM D-92-66)
- Closed Cup (Grit-0'Cobs Granules) 396°F (ASTM D-93-71)
Flash Point - Open Cup (Grit-0'Cobs Granules) 350°F (ASTM D-92-66)
- Closed Cup (Grit-0'Cobs Granules) 388°F (ASTM D-93-71)
Minimum Explosive Concentration 0.045 (U.S. Bureau of Mines
.. (-200 Mesh Grit-0'Cobs Dust Cloud) oz/cu ft Report 5624)
238
-------
COMPANY NAME Carborundum Company
Insulation Division
P.O. Box 808
Niagara Falls, NY 14302
PRODUCT NAME Ceramic Fiber Paper, Board, Cloth, Rope
APPLICATIONS
Cloth
Furnace curtains
Expansion joints
Welding cloth
Pipe and hose wraps insulation (tape and sleeving)
Equipment and personnel protection
Maintenance cloth
Rope
Door seals - furnace ovens
Flange and burner gaskets
Static packings
Paper
Electric and thermal insulation for transformer coils
Thermal insulation for oven appliances (self-cleaning)
Tap out cones for molten aluminum
Flat gasketing
Expansion joint material
Muffler insulation
Fiberboard
Thermal protection in large circuit breakers
Fireproofing for commercial and residential security boxes,
safes, and files
Aluminum pouring trough cover and liner
239
-------
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Textiles
Color - White
Composition - Alumina/silica
Continuous use limit - 2300°F
Melting point - 3200°F
Breaking strength (rope) - 80 Ibs
Organic content <- 20 to 25 percent
Paper
Composition - Alumina/silica
Organic content - 6 to 10 percent
Tensile strength - 120 psi
Burst strength - A Ibf
Density - 10 to 20 lb/ft3
Continuous use limit - 1300. to 2600°F
Thermal conductivity - 0.36 at 400°F
Board
Composition - Alumina/silica
Continuous use limit - 2300°F
Tensile strength - 180 psi
Organic content - 6 to 7 percent
Thermal conductivity - 0.53 at 400°F
COSTS IN PRODUCTION
Information not supplied.
COSTS IN USE
Information not supplied.
HEALTH INFORMATION
Not supplied.
240
-------
BIBLIOGRAPHIC INFORMATION
Not supplied.
MANUFACTURER'S CONTACT
B.J. Glazier or K.C. Pietak
Carborundum Company
Insulation Division
P.O. Box 808
Niagara Falls, NY 14302
241
-------
COMPANY NAME
PRODUCT NAME
*
Celanese Plastics and Specialties Company
26 Main Street
Chatham, NJ 07928
(201) 635-2600
Celiox™ Fibers
TM
Celiox fibers are heat stabilized polyacrylonitrile which has
been subjected to a treatment that results in cyclization,
crosslinking and oxygen addition.
APPLICATIONS
Some applications are:
Protective garments
Fire proximity suits
Heat resistant gloves
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Typical Celiox Filament Properties
Density, g/cc
% Moisture Regain, (65% RH)
Electrical Resistivity, Ohm-cm
Tensile Strength
g/denier
psi, x 103
Tensile Modulus
g/denier
psi, x 10
Elongation, %
Color
Response of Celiox to Heat
Limiting Oxygen Index
Flammability in Air
AATTC Method 5903
Melting Point
1.4
10
>1010
1.7
30.5
90
1.6
10
Black
50% 02 required to
sustain ignition
Does not ignite
No afterglow
Zero char length
Converts to carbon
Sublimation Point 6600°F
(3650°C)
242
-------
Exposure to Molten Metal*
Aluminum @ 1400°F
Steel <§ 2850°F
Runs off fabric at 70° angle,
no burn through
Runs off fabric at 70° angle,
no burn through
Horizontal fabric withstands
1 Ib. spash without burn
through
Other Properties
Celiox fibers may be readily converted into carbon fibers. High tempera-
tures convert Celiox fiber from a heterocyclic polymer to pure carbon. The
reaction is rapid at temperatures above 600°F (360°C). Under controlled
conditions, the carbon fiber can develop strength and modulus several times
that of the starting fiber but at a sacrifice in elongation. Carbon fabrics
find uses as reinforcement of ablative and structural composites for high
temperature service in aircraft disc brakes and rocket nozzles.
RESEARCH AND DEVELOPMENT
Information not supplied.
COSTS IN PRODUCTION
Information not supplied.
COSTS IN USE
Has processability on conventional textile equipment.
HEALTH INFORMATION
Not supplied.
MANUFACTURER'S CONTACT
Mr. W.D. Timmons
Celanese Plastics and Specialties Company
26 Main Street
Chatham, N.J. 07928
TM
Gentex Dual-Mirror aluminized fabric, 13 oz/yd2 Celiox fiber.
Gent ex Corp., Carbondale, Pa.
243
-------
COMPANY NAME E. I. DuPont de Nemours and Company, Inc.
Wilmington, DE 19898
PRODUCT NAMES Kevlar®and Nomex®Aramid Fibers
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
FIBER/FORM:
PHYSICAL PROPERTIES FILAMENT
Density, gm/cc 1.45
Denier/Filament 1 . 5
Filament Dia., mils .47
Filament Length, Ins. Cont.
Tenacity, gm/denier 22
Tensile Strength,
psi x 10- 3 400
Modulus, psi x 10" 6 10
Elongation, % 4
THERMAL PROPERTIES
Shrinkage % at
177°C. (350°F)
285°C. (545°F)
In flames
(815°C. or 1500°F)
Max. Continuous use
Temp. °C
OF
Decomposition
Temp. °C.
op
KEVLAR® NOME3
STAPLE CHOPPED,
YARN PULP FILAMENT
1.45 1.45 1.38
1.5 1.5 1.5
.47 <.47 .50
1.5-4.0 .08-. 25 Cont.
9-13 £22 5.3
160-230 <400 100
10 10 2.5
5 4 22
0
0.5
0.5
150-205
300-400
-480
-900
:®
STAPLE
YARN
1.38
1.5
.50
1.5-3.0
3.5-4.5
65-80
1.3-2.2
35-22
<1.0
2.5
>40
205-260
400-500
-425
-800
Limiting Oxygen
Index (LOI)
29
29
244
-------
DISC BRAKE PADS
-7
2.6-
-6
2.0-
-5
Md hp-hr
WEAR
WEAR |SJA RATE
RATE ^
1.0-
0.5-
I
/
/ COMMERCIAL
/ ASBESTOS BASED
-3
CONTROL
TRUCK BLOCK
IIX WITH !
KEVLAR*
• MIX WITH 2*4
- 2
- I
MIX C WITH
5% KEVLAR*
> GMSEMI
METALLIC
400
204
900 600
260 316
700 800
371 427
900 1000 *F.
482 538 *C
DRUM TEMPERATURE
High temperature wear
.6
0 C
5
LL. ,1
fe
i- .3
E
U n
It'
° 1
<-> .1
0
BASELINE
200eF±20eF
(93-c±irc:
•-.
___^
M
_
-APPL. NO.
5 10 15
I l i
.6
O i-
5
Of Jl
u-.l
u.
O
1 "Z
ft"
—.2
y^
S.1
n
FIRST RUN
FADE RECOVERY
^ rTr^^^
~s^
i— —
—
— DRUM TEMPERATURE
250 350 150 550 150 350 250T
1 1 1 1 1 1 1 1 l l 1 1 1
" c
P5
LJ
O
i_ 3
5'
—.2
j_
LU
ILJ. 1
n
WEAR TEST
100°F ± 20'F
~ (201°C ± U°C)
^^^^.^ — • — 1_
— APPLICATION NUMBER
10 20 30 10 50 60 70 80 90
1 1 1 1 1 1 1 l 1
121
COEFFICIENT OF FRICTION
Oh-* *4 v*i «• in en
SECOND RUN
FADE RECOVERY
X
DRW TEMPERATURE
250 350 150 550 650 550 159 350 250T
' ' ' t I- I. 1 1 I l l l i i i i i
.6
sr
u.
o
S'3
I-2
LU
S.I
0
FINAL BASE-
LINE 200°F±
" 20'F
(93°C±irC)
APPL, NO.
" 5 10 15
l i 1
121 176 232
343 238 232 176 121'
J661A test plots (Chase test)
245
MIX A*
MIX A' WITHOUT
KEVLAR* FIBER
PREMIUM COMMER-
CIAL ASBESTOS
CONTROL
-------
KEVLAR* ARAMID FIBER
to
•e-
a\
APPLICATION:
PERFORMANCE
Fiber Content, %
Specific Gravity
Coef. of Friction
Friction Fade
Wear Resistance
Wear on Mating
Surface
Thermal Conductivity
Creep
Coef. of Thermal
Expansion
Thermal
Fabrics
(Gloves &
Curtains)
Clutch
Facings
Brake
Pads
Friction
Papers
Gaskets
(Beater -
Add &
Compressed)
Plastics
Reinf mt .
100
1.45
N/A
N/A
Excellent
N/A
low
N/A
20-30
1.6-2.2
.2 - .6
Stable
Excellent
low
low
low
2-5
1.6-2.2
.2 - .6
Stable
Excellent
low
low
low
5-15
1.6-2.2
—
Stable
Excellent
low
low
low
3-6
1.5-2.0
N/A
N/A
—
low
N/A
low
N/A
low
low
low
low
2-50
1.3
N/A
N/A
Excellent
low
N/A
low
low
-------
NOMEX ARAMID
APPLICATION:
Product Form:
PERFORMANCE
Specific Gravity
Coef. of Thermal
Expansion
Thermal Conductivity,
BTU. in/hr. ft. 2 °F
Dielectric Strength,
Volts/mil
Resistance to Acid
Resistance to Caustic
Resistance to Solvent
Limiting Oxygen Index
Thermal
Insulation
Fiber
Protective
Clothing
Fiber
Electrical
Insulation
Fiber
1.38
low
.24
N/A
Good
Good
Excellent
29
1.38
Low
.24
N/A
Good
Good
Excellent
29
.3-1.38
Low
.3 - .8
850
Good
Good
Excellent
24-32
COST IN PRODUCTION
Information not supplied.
COST IN USE
KEVLAR<8> ARAMID FIBER (1980 or ices)
APPLICATION;
Fiber Price, S/lb.
Lifetime Cost,
Asbestos • 1.00
Thermal
Fabrics
(Gloves &
Curtains)
5.75
1.00
Clutch
Facings
5.50
.60-1.00
Brake
Pads
3.75-5.00
.60-1.00
Friction
Papers
3.75
1.00
Gaskets
(Beater -
Add &
Compressed)
3.75
1.05-1.50
Plastics
Reinfmt.
3.75-5.75
1.00-1. 10
NOMEX® ARAMID
APPLICATION;
Product Form:
Price, $/lb.
Lifetime Cost,
Asbestos = 1.00
Thermal
Insulation
Fiber
6.10-19.00
.90 - 1.20
Protective
Clothing
Fiber
6.10-19.00
1.30 - 1.50
Electrical
Insulation
Fiber
6.43-14.26
1.50-3.00
247
-------
HEALTH INFORMATION
KEVLAR*8 Aramid Fiber Material Safety Information
Kevlar®aramid is an aromatic, organic composition of carbon, hydrogen,
oxygen and nitrogen. When burned, its combustion products are similar to
those of other organic materials comprised of the same four elements; their
exact composition depends on the conditions of combustion (temperature,
availability of oxygen, etc.). Kevlar®yarn is not readily biodegradable
and contains no significant percentage of material extractable in water so
its effect on ground water in case of landfill disposal should be negligible.
Kevlar®yarns as supplied by Du Pont have been tested for toxicity by skin
contact tests on animals and humans. No toxic reactions have been observed.
We have received no reports of skin irritation or other health hazard associ-
ated with this fiber during six years of extensive market development activity
involving millions of pounds of fiber used in a variety of applications.
Kevlar®is not radioactive, is stable in all recommended use environments and
requires no special spill procedures. In handling yarns of Kevlar^ operators
should be cautioned of the unusually high strength of this product and the
resultant possibility of cuts to hands or fingers caught in loops and tangles.
NOMEX® Aramid Fiber Material Safety Information
Nomex®aramid is an aromatic organic composition of carbon, hydrogen, oxygen,
and nitrogen. Nomex® is difficult to ignite and will usually self extinguish
in the absence of an external heat source. However, when burned, its combus-
tion products are similar to those of other organic materials comprised of the
same four elements; their exact composition depends on the conditions of
combustion (temperature, availability of oxygen, etc.). Nomex®is not readily
biodegradable and contains no significant percentage of materials extractable
in water so its effect on ground water in case of landfill disposal should be
negligible.
Nomex® fiber supplied by Du Pont has been tested for toxicity by skin contact
tests on animals and humans and by inhalation and feeding tests on animals.
No toxic reactions have been observed.
Nomex®fiber is not radioactive, is stable in all recommended use environments,
and requires no special spill handling procedures.
BIBLIOGRAPHIC INFORMATION
Not supplied.
248
-------
MANUFACTURER'S CONTACT
®
For Kevlar Aramid Fibers
John C. Norman
Textile Fibers Department
Centre Road Building
Wilmington, DE 19898
Phone: (302)999-3546
For Nomex Aramid Fiber
Isaac L. Gadsden
Textile Fibers Department
Centre Road Building
Wilmington, DE 19898
Phone: (302)999-3951
249
-------
COMPANY NAME Evans Products Company
Forest Fiber Products Group
Glass Fiber Division
1115 S.E. Crystal Lake Drive
Corvallis, OR 97330
(503) 753-1211
PRODUCT NAME EVANITE Glass Fiber
EVANITE Glass Fiber is produced in bulk form for the manufacture on
100 percent glass paper and as a furnish additive for cellulose and synthetic
media. EVANITE fibers are produced by a rotary flame attenuation method as
discrete filaments of varying length. The fibers are available in 12 grades
ranging from 0.30 to 9.00 microns in diameter. EVANITE fiber is free of
binder and surface sizing additives. Water content is negligible.
APPLICATIONS
EVANITE has been used since 1976 for the manufacture of 100 percent
glass fiber paper and as a cellulosic furnish additive to enhance sheet
characteristics. Due to the wide range of fiber grades available, EVANITE
may be used for such applications as:
• High Efficiency Filtration Media (HEPA)
• Medium Efficiency Filtration Media
• Industrial and Surgical Respirator Media
• Battery Separators
• Cryogenic Insulation
• High Efficiency Thermal and Acoustical Insulation
• Corrosion Resistant Media
• High Temperature Media
The coarser grades of EVANITE may be used as a partial replacement for
chopped strand in many applications.
Furnish Additives
EVANITE may be used as an additive to standard cellulosic furnishes to
improve or modify various sheet characteristics, including:
• Porosity
• Tear Resistance
• Machine Shrinkage
• Wet Tensile Strength
250
-------
• Pulp Drainage Rate
• Dimensional Stability
• Drying Rate
• Bulk
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Glass Fiber Grades
EVANITE Glass Fiber is available in the following standard grades:
Average fiber
diameter* (microns)
0.30
0.45
0.60
0.75
0.90
1.60
2.70
3.20
4.50
5.70
7.20
9.00
GLASS COMPOSITIONS
The fiber grades are produced from two borosilicate glass compositions
distinguished primarily by their ability to withstand acid attack:
• B Glass—Standard borosilicate. Normally specified for
Grades 0250-2500.
• C-Glass—A special, acid resistant composition normally
specified for Grades 3000-9000.
Grade
0250
0500
1000
1500
2000
2500
3000
4000
5000
6000
7000
9000
Reference
AAAA
AAA
AA
A
B
C
D
E
G
*Based on typical average values as determined by EP tests 02-006 and 02-003
calibrated by actual SEM observation.
251
-------
PROPERTIES
B-Glass C-Glass
Specify Gravity 2.55 2.50
Service Temperature 545°C 565°C
(Estimated)
Softening Point* 703°C 735°C
*ASTM C 338.
CHEMICAL DURABILITY
The EVANITE C-glass composition was developed specifically to withstand
extremely harsh acid environments. Both glass compositions perform relatively
well in mild alkaline conditions. Performance data, as determined by EP
Method 03-002*, are:
Glass Acid Alkaline
B 10.0 8.0 Maximum %
C 2.0 11.0 Weight Loss
*72 hour Immersion at 77°C
Acid-1.28 s.g. HaSOi,
Alkaline-ph 10 NaOH
Weight loss associated with immersion in excess of 72 hours is
negligible.
SERVICE TEMPERATURE
Depending on the level of product shrinkage tolerable, EVANITE may be
used at elevated temperatures in excess of 500°C. EVANITE has also been
successfully tested at cryogenic temperatures.
PAPER MAKING CHARACTERISTICS
The EVANITE fiber grades have been developed for use on conventional
paper making equipment with only minor adjustments necessary to deal with
differences in drainage rates, drying time, and shrinkage characteristics.
252
-------
DISPERSION
EVANITE disperses exceptionally fast and with a minimum energy input.
Every attempt should be made to agitate with care. Beater speed and time
should be set at the lowest levels necessary to produce a homogeneous
slurry. In this manner, fiber damage will be minimized and the resulting
sheet characteristics improved.
EVANITE disperses optimally at a water temperature range of 28 to 32°C
and pH 2.8 to 3.5. However, the fiber can be easily dispersed at near-
neutral pH.
CONSISTENCY
Fiber concentration should be maintained at minimal levels to reduce
fiber damage caused by abrasion during beating. Consistency levels of
approximately 0.75 to 1.00 percent in the mixer and 0.05 to 0.10 percent at
the headbox are desirable.
COSTS IN PRODUCTION
Information not supplied.
COSTS IN USE
Cost of EVANITE glass fiber as of May 15, 1980.
Grade Price/lb Grade Price/lb
0250 $7.79 3000 $1.14
0500 6.23 4000 0.93
1000 3.26 5000 0.67
1500 2.34 6000 0.66
2000 2.18 7000 0.65
2500 2.00 9000 0.63
HEALTH INFORMATION
Not supplied.
BIBLIOGRAPHIC INFORMATION
Not supplied.
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MANUFACTURER'S CONTACT
Alan J. Gnann
Evans Products Company
Forest Fiber Products Group
Glass Fiber Division
115 S.E. Crystal Lake Drive
Corvallis, OR 97330
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COMPANY NAME GRC Products, Inc.
17051 IH 35 North
Drawer J
Schertz, Texas 78154
(512) 651-6773
PRODUCT NAME GRC Flat Sheet
GRC is an asbestos-free Glassfiber Reinforced Cement product made by
reinforcing a mixture of ordinary Portland cement and a fine aggregate, with
alkali-resistant glass fiber. The glass fiber used for the reinforcement of
the cement matrix was developed by the British Research Establishment and
Pilkington Brothers, Limited of St. Helens, Merseyside, England, to resist
the alkali produced during the normal setting and hydration processes in
Portland cement.
APPLICATIONS
A few of the many applications of GRC are:
Carrier board for laboratory tunnel tests
Electric closet linings
Fire resistant linings
Industrial wall partitions
Fume hood liners
Lost form work
Tunnel linings
Commercial and industrial use as spandrels, soffits, fascia panels
Commercial and industrial sandwich panel wall systems
Pizza oven liners and shelves
Highway noise control/noise barrier
Rooftop walkways
Livestock products
Feed troughs
Sheep dips
Pig slurry channels
Insulated pig pen slabs
GRC has satisfactory performance at high temperatures for short periods
of time. The maximum service temperature of GRC is in excess of 600°F.
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PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
GRC has properties similar to those of asbestos-cement with one notable
exception; impact strength, in which GRC is approximately 10 times stronger
than asbestos cement. All current GRC formulations will satisfy ASTM 136 as
regards noncombustibility and will be rated 0 on all characteristics measured
by ASTM E84.
The results of tests performed on GRC by an independent outside testing
laboratory are listed below:
Dimensions of test coupon - 1/4" x 2 1/4" x 14"
Dry Density, PCF - 124.2
Normal moisture content (% of dry weight) - 2.3
Water absorption (% of dry weight) - 4.9
Modulus of elasticity, PSI - 2.4 x 106
Transverse strength, PSI (MOR) - 3300
Compressive strength, PSI - 18,000
Tensile strength, PSI - 2200
Shear strength, PSI - 5300
Brinnel hardness - No. 29
Dimensional change due to moisture (in./in.)
Shrinkage - normal to dry - 0.0014
Expansion - normal to 90% RLF - 0.0004
Expansion - dry to saturated - 0.0015
Thermal expansion (in./in./°F) - 1.3 x 10~6
Maximum service temperature in excess of 600°F.
All tests and calculations were performed in accordance with ASTM
standards C-220, C-459, and C-580.
PERFORMANCE STANDARDS
At this point of time, there are no government or industrial performance
standards to be met by the GRC product.
RESEARCH AND DEVELOPMENT
Although GRC is being evaluated as a substitute product in many areas,
the basic material (glass fiber reinforced cement) is backed by over 12 years
of service and laboratory testing; consequently, GRC is considered a developed
material.
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COSTS IN PRODUCTION
GRC sheet can be cut and machined with tools suitable for masonry and
asbestos cement use. Fabrication of GRC should not require retooling or
supplying of new equipment.
Except for the actual price differential between GRC and Asbestos Cement,
there should be no change in production costs of using GRC over asbestos cement,
COSTS IN USE
A full range of GRC flat sheet is commercially available. Standard
thicknesses of 1/8, 1/4 and 3/8 inch are available from inventory in
4 foot by 8 foot sheets and 4 foot by 10 foot sheets.
GRC sheets are priced on a per square foot basis. Our current quantity
prices are as follows:
• 1/8 inch - $0.60 ft2
• 1/4 inch - $0.80 ft2
• 3/8 inch - $1.05 ft2
(These prices subject to change without notice.)
There is no question that with further restrictions or a total restric-
tion of the use of asbestos cement sheets resulting in an increased produc-
tion of GRC, the price of CIRC could decrease by as much as 15 to 20 percent.
GRC, having the same excellent general properties as asbestos cement
sheet, such as good mechanical strength and chemical resistance, rot proof,
fire resistance, heat resistance, and good machining qualities, should
perform comparably to asbestos cement sheets with essentially no increase
in cost of installation, maintenance and replacement.
HEALTH INFORMATION
The reinforcing material of GRC, Cem-Fil AR glass fibers, do not
present any known health hazard during manufacture, installation, on-site
working or long term weathering.
BIBLIOGRAPHIC INFORMATION
Additional commercial and technical information on GRC can be obtained
from the following sources:
Pilkington Brothers, Ltd.
Cem-Fil Marketing
St. Helens, Merseyside, England
Cem-Fil Corporation
120 Spence Lane
Nashville, Tenn 37211
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MANUFACTURER'S CONTACT
GRC Products, Inc.
17051 IH 35 North
Schertz, Texas 78154
Mr. Frank W. Fekete
Mr. Bill Lewis
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COMPANY NAME Hill Brothers Chemical Company
One City Blvd. West, Suite 1521
Orange, California 92668
PRODUCT NAME HiFibe
APPLICATIONS (for HiFibe in general)
• Caulks Sealants
• Gasket Forming Compounds
• Cements
• Filler in Plastics
• Swimming Pool Plaster
• Interior and Exterior
Plaster and Stucco
• Polyester Resin Filler
• Putty
• Glazing Compounds (Window)
• Crack Filler
• Asphalt Coatings and Cements
• Textured Paints
Underbody Spraying Mastic
• Mastic
• Block Fillers
• Joint Cements
• Paints
• Vinyl Moulding Compounds
• Taxidermy
• Fiberglass Boats
PRODUCT NAME HiFibe 250, 270, 290
Description
HiFibe 250, 270 and 290 are high fiber content fillers. The fiber
in these fillers is HiFibe 2000 which has been dispersed in an inert filler.
The method of dispersion insures a very uniform product which does not sep-
arate upon mixing. These fillers work well in either water or oil-based sys-
tems and show very low shrinkage upon drying.
APPLICATIONS (for HiFibe 250, 270, 290)
As a fibrous filler in cements, caulks, puttys, taping muds, and poly-
ester resins. In asphalt coatings, textured paints, mastics, glazing compounds,
and anywhere a high fiber content filler is needed.
RESEARCH AND DEVELOPMENT
We have a staff of chemists working on new formulations and uses of
HiFibe.
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PHYSICAL PROPERTIES/PERFORMANCE/TEST- RESULTS
Specifications 250 270 290
Bulk density (Ib/cu. ft) 39 39 37
Oil absorption 88 106 110
Water absorption 84 100 112
Burn rate Fiber chars, will not sustain flame
Moisture content <1% <1% <1%
Color White White White
% fiber 5% 7% 9%
% inert fillers -95% -93% -91%
Limitations
HiFibe should not be used where temperatures exceed 115°C.
Physical Properties
The fiber content of HiFibe varies from 1 percent to 100 percent by
weight.
Another major component of HiFibe is C. P. California talc from
Pfizer Minerals. The grades of fibers used in HiFibe have average lengths
from 0.7 mm to 2.5 mm with an aspect ratio of about 20. These fibers have
average coarseness values between 7 and 15 decigrix (1 decigrix = 1 mg/100 mg)
This is equivalent to 0.6 to % denier. The branched or fibrillated nature of
the fiber results in a very soft flexible fiber.
HiFibe is not designed to resist abrasion, acid and base corrosion
or as a noise and thermal insulation.
COSTS IN PRODUCTION
There should be no additional costs for retooling, equipment changes,
etc., as no process change would be anticipated.
COSTS IN USE
Depending upon the application, HiFibe will cost about the same as, to
twice the cost of using asbestos. Depending primarily upon the percent of
synthetic fiber in the HiFibe, the cost of the product at our Los Angeles
plant would be 12$ to $2.00 per pound.
If the government chose to restrict the use of asbestos, this would not
change the price appreciably.
If used as recommended, the product produced with HiFibe should have a
lifetime cost the same as asbestos.
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HEALTH INFORMATION
It is Hill Brothers Chemical's belief that all inhaled dust can be harm-
ful, therefore, we recommend that a dust respirator be worn when handling
HiFibe to avoid inhalation of the dust.
BIBLIOGRAPHIC INFORMATION
The fiber used in HiFibe is high density polyethylene. A booklet titled
"Fybrel Synthetic Fiber" published by Crown Zellerbach, Chemical Products
Division, Vancouver (Orchards) Washington, 98662, describes a HiDensity
Polyethylene Fiber in detail.
MANUFACTURER'S CONTACT
Contact Mr. Dean Hill, International Headquarters, Hill Brothers Chemical
Company, One City Boulevard West, Suite 1521, Orange, California 92668,
phone, Area Code 714, 634-3322.
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COMPANY NAME HITCO Materials Group
1600 W. 135th Street
Gardena, CA 90249
PRODUCT NAMES Refrasil (silica textile products)
Carbon and graphite continuous filament yarns
REFRASIL/TECHNICAL CHARACTERISTICS
Applications
• Weld Protection
• Furnace Curtains
• Personnel Shields
• Separator Cloth
• Expansion Joints
• Thermocouple Insulation
• High Temperature Seals/Gaskets
• Hose and Cable Insulation
• Furnace Linings
• Reformer Insulation Containments
Generally speaking, Refrasil can be substituted for asbestos in the
same textile product form and provide increased insulation and thermal
stability in higher temperatures. Standard Refrasil products can withstand
temperatures to 1800°F, whereas asbestos Commercial and Underwriters Grades
are only rated at 450°F.
Refrasil is not recommended for safety clothing or protective garments
where seam strength and flexing are critical to the integrity of the garment
and safety of the wearer. The low break strength and abrasion resistance
of Refrasil cloth restricts the application in safety garments to accessories,
such as aprons, gauntlets, leggings, etc., where seam strength and abrasion
are not critical to the performance of the article.
PHYSICAL PROPERTIES AND PERFORMANCE CHARACTERISTICS
• Chemical analysis - 96 percent minimum SiC*2, traces
of metallic oxides.
• Temperature limit - 1800°F before embrittlement occurs.
• Thermal Conductivity - 0.6 Btu/hr/ft2/in./°F at 400°F
to 1.5 Btu/hr/ft2/in./°F at 1800°F.
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• Specific Heat - 0.28 Btu/lb/°F average
• Linear Shrinkage - 2 percent to 12 percent depending upon peak
temperature ranges from 800°F to 1800°F.
• Chemical Resistivity - relatively inert to most chemical
environments, including acids, except flourine gases and
some molten metals such as magnesium, sodium and silicon.
• Permeability (UC 100-96 cloth) - 5.3 cu ft/min/sq ft.
• Abrasion Resistance (UC 100-96 cloth) - 229 cycles.
• Dielectric Strength - 40 volts/mil
• FTM Std. 191, Method 5304 Wyzenbeck Unit, 2 Ib load, 2 Ib
tension, 600 grit paper.
For complete properties and performance characteristics of Refrasil, refer
to "Technical Data Bulletin - Engineering Data LHT/MD-3979R."
PERFORMANCE STANDARDS
• MIL-I-24244 Chloride Acceptability
• 40 CFR 164.009 Incombustible Materials
• NNSY 383/IM Refractory Cloth, 2000°F intermittent service,
nonasbestos (Norfolk NSY).
RESEARCH AND DEVELOPMENT
The areas in need of improvement in the silica textile products include
abrasion resistance and break strength. The material provides thermal per-
formance to 1,800°F and beyond (with special treatments), but fails to pro-
vide the durability to withstand the normal industrial environments. Various
surface coatings and impregnations have been applied in an effort to improve
abrasion resistance and lubricate the individual fibers to reduce failure from
flexing.
REFRASIL/ECONOMIC INFORMATION
Costs in Production
In most instances, there is no need for process changes when substituting
Refrasil for asbestos textiles in the same form (cloth, tape, sleeving, etc.).
The elimination of costs for asbestos compliance usually result in a reduction
of overall costs, in spite of the higher (two to three times) initial cost of
material for Refrasil over asbestos products.
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Costs in Use
The average selling prices of Refrasil in the various product forms
available are:
Cloths - $14 to $28/lineal yard
Tapes - $0.40 to $1.60/lineal foot
Sleevings - $2.25 to $5.50/lineal foot
Yarns and Cordages - $26 to $36/pound
Fiber - $10/poiind
Batt - $3.75 to $4.50/square foot
Rope - $0.25 to $5.00/lineal foot
Prices vary within product forms due to variables of thicknesses, sizes, and
quantities purchased.
Costs of producing Refrasil are directly related to the costs of raw
material (leachable glass fiber textile products) and labor. Current
pricing policies of the weaver and glass fiber producers do not indicate
any cost reductions from increased production volumes.
REFRASIL HEALTH INFORMATION
Due to the size of Refrasil fibers (8 microns in diameter) the possibility
of inhaling fibers into the lower respiratory tract is minimized. Therefore,
it is believed that with reasonable precautions applied to the handling and
use of Refrasil, no health hazard or concern for safety exists. Reference
"Technical Data Bulletin - Safety and Health Considerations" LHT/MD-3879
for complete data.
CARBON AND GRAPHITE CORDAGE/TECHNICAL CHARACTERISTICS
Applications
Compression packings (braided)
High Temperature .door seals
Vacuum furnace lining thread
The primary use for carbon and graphite filament yarns is in the
production of braided mechanical packings for service temperatures above
550°F and highly corrosive environments. Due to the presence of TFE and
other organics that serve as lubricants for braiding, these products are
not recommended for applications where high-purity and nonhalogens are a
requisite (such as nuclear applications).
264
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PHYSICAL PROPERTIES AND PERFORMANCE CHARACTERISTICS
Carbon Graphite
Carbon assay (wt %) 92 99
Ash Content (wt %) 0.5 0.5
Breaking strength (Ib) 15 (10 ply) 30 (20 ply)
Diameter (in.) 0.05 (10 ply) 0.08 (20 ply)
Yield (yd/lb) 700 (10 ply) 350 (20 ply)
Modulus (lb/in.2 x 106) 6 6
Tensile (lb/in.2 x 103) 120 120
Chloride content - Less than 50 ppm
Carbon and graphite cordage resists chemical attack except from highly
oxidizing substances.
COSTS IN PRODUCTION
Generally, there are no process or manufacturing changes required for
carbon and graphite braiding operations. The packing manufacturers may
vary lubricants and other additives as it applies to their specific braiding
process or equipment.
COSTS IN USE
The carbon and graphite yarns are expensive, but intended for special
high-performance braided packings or seals. The average selling prices are:
• Carbon cordage (10 ply) - $25/lb
• Carbon cordage (20 ply) - $22/Ib
• Graphite cordage (10 ply) - $35/lb
• Graphite cordage (20 ply) - $32/Ib
The superior thermal performance and chemical resistance of carbon and
graphite materials allows substitution for asbestos in more critical valve
and pump sealing applications with the assurance of longer more reliable
service and less frequent replacements due to thermal or corrosion failures.
Overall cost comparisons with asbestos .packings may be available from the
braided packing manufacturers.
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HEALTH INFORMATION
Carbon and graphite cordage materials are electrically conductive and can
cause interference to electronic signals and communications. Consequently, pre-
cautions against indiscriminate disposal of materials are advisable.
BIBLIOGRAPHIC INFORMATION
For complete properties and performance characteristics of Refrasil,
refer to "Technical Data Bulletin-Engineering Data LHT/MD-3979R."
MANUFACTURER'S CONTACT
Robert E. Portik,
HITCO Materials Group
1600 W. 135th Street
Gardena, CA 90249
(213) 321-8080
266
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COMPANY NAME Janos Industrial Insulation Corporation
80 West Commercial Avenue
Moonachie, New Jersey 07074
PRODUCT NAMES Nu Board 1800
This is an asbestos-free board made from mineral fibers and silica.
Thermonol Textiles
These are replacements for commercial grade asbestos cloth, uscable for
temperatures up to 650°F.
Glastemp Textiles
This line of glass textiles can replace asbestos up to AA grade.
Siltemp Textiles
This is a product line of high-temperature textiles for replacement of
AAA grade asbestos. It can be utilized for temperatures up to 3000°F.
Cem-Fil GRC/125
This product ds being used as a replacement for asbestos-cement sheets.
It is manufactured in the same sizes, and can also be molded to fit various
specifications.
Glasspaper
This product is being utilized to replace asbestos paper rolls for the
home consumer.
APPLICATIONS
Some typical uses for Nu Board 1800
• Lining furnaces • Cores for metal clad doors
• Moving picture booths • Stove pads* welding pads
• Elevator shafts • Incinerators
• Ceilings, walls exposed to heat • Heater lining
• Gaskets • Strongbox lining
• Stoves • Kiln lining
• Electric ovens • Molded for troughs
• Glass Lehr rolls • Cable protection
• Float glass conveyor rolls
267
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Uses for Thermonol Textiles
• protective garments, weld curtains, insulation barriers,
insulation pads, sleeving for thermocouples, cable tapes,
gaskets for wood-burning stoves.
Uses for Glastemp Textiles
• weld shields, gaskets, stress relieving applications, safety
blankets, protection of flexible hose, door seals, tadpole
gasketing, packing furnace doors.
Uses for Siltemp Textiles
• same as listed above only for higher temperatures.
Uses for Cem-Fil GRC/125
• mounting of electrical equipment, bakery ovens, casings
over boilers, cooling towers, skirting on buildings,
machined parts.
Uses for Glasspaper
• wrap paper for fire protection, protection for soldering,
welding, lining barbecue pits, wrapping gas tanks for storage,
iron rests, muffler wrap.
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Physical Properties of Nu Board 1800 (nominal);
• Color - Beige
• Density - 66.8 lb/ft3
• Tensile strength - 711 lb/in.2
• Flexural strength - 1280 lb/in.2
• Compression at 3000 psi - 30 to 40 percent
• Ignition loss - 20 percent max
• Moisture content - 3 percent
• Thermal conductivity - 0.0636 Btu/hr/ft/°F
• Flammability - Will not burn
• Heat resistance - Up to 1800°F dependent upon application
Dimensions
• Thickness range - inclusive 3/32" to 1/2"
• Sheet size - 40" x 40"
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COSTS IN USE
Nu Board 1800
20 to 25 percent higher than the existing asbestos sheets, however, it
has a longer life at higher temperatures.
Thermonol Textiles
Approximately 10 to 15 percent above asbestos prices.
Glastemp Textiles
5 to 10 percent higher than asbestos price.
Siltemp Textiles
Approximately 30 to 35 percent higher than asbestos.
Glasspaper
Approximately same as asbestos.
COST IN PRODUCTION
Information not supplied.
HEALTH INFORMATION
Not supplied.
BIBLIOGRAPHIC INFORMATION
Not supplied.
MANUFACTURER'S CONTACT
T.J. Connolly
Janos Industrial Insulation Corporation
80 West Commercial Avenue
Moonachie, New Jersey 07074
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COMPANY NAME . Manning Paper Company
P.O. Box 328
Troy, New York 12181
PRODUCT NAME Manniglas 1200, 1400, 1270, 1276, and 1277 material
APPLICATION
Application examples:
Manniglas 1200 and 1400 have an Underwriters' Laboratories 94V-0
recognition and are suitable products where this test criteria is important
to the end product.
Pneumatic tube bundle heat protection wrap light fixture heat shields
when laminated to aluminum foil.
Hand held hair dryers and other appliance heat shields with and
without foil lamination.
Components of tape composites for high temperature cable wrap.
Manniglas 1276 for skin applications on:
(a) urethane and isocyanurate
(b) rigid foam boards—vinyl laminations substrate to impart
flame barrier
(c) glass bat or compressed mat flameproof surface skin to
impart smoother surface
PHYSICAL PROPERTIES/PERFORMANCE/TEST RESULTS
Glass fiber temperature limitations are in the 1300-1500°F range. At
these temperatures the product will soften and the glass will melt at 1500°F.
Glass fiber papers are lower in density than asbestos fiber papers and
consequently are a much lower actual weight. Usual estimates are one-third
the weight range of the asbestos materials and therefore overall coverage
costs are usually competitive with current asbestos materials.
PERFORMANCE STANDARDS
Manniglas 1200 and 1400 have an Underwriter's 94V-0 recognition.
RESEARCH AND DEVELOPMENT
Information not supplied.
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COSTS IN PRODUCTION
Information not supplied.
COSTS IN USE
Cost varies from lie to 13$ per square foot, depending on thickness of
the material.
HEALTH INFORMATION
Not supplied.
BIBLIOGRAPHIC INFORMATION
Not supplied.
MANUFACTURER'S CONTACT
John M. North
Manning Paper Company
P.O. Box 328
Troy, New York 12181
(518) 273-6320
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COMPANY NAME NEWTEK INDUSTRIES, INC.
P.O. Box 25
Victor, New York 14564
PRODUCT NAME ZETEX™
APPLICATIONS
Curtains: welding, fire, drop, oven
Blankets: stress relieving, welding, thermal insulation,
safety
Industrial: expansion joints, electrical insulation,
piping insulation, gas and liquid filtration,
scrubbers, acoustical insulation, reinforcements,
laminates, folded and rubberized gaskets.
Safety: garments, gloves, mittens, spats, sleeves,
aprons
Engineered
Products: door seals, tad-pole gaskets, pads, etc.
Applications in which the product may not work are those in which cut-resis-
tance of the material is required; e.g., gloves and mittens. The products
can be reinforced with leather or an additional layer of ZETEX as is com-
monly done with asbestos.
PHYSICAL PROPERTIES
Content: Silica-based highly textured yarn
Fiber shape and size: Round with 6 to 9 micron filament
Dielectric characteristics: Dielectric constant of 5.9 to 6.4
Strength: 500,000 psi at 72°F
Elongation: Approximately 5% for yarn
Resistance to abrasion: Taber abrasion tester, CS17 Wheels,
1000 Gm/Wheel
ZETEX 1200 - 493 cycles to failure
ZETEX 1200XP - 1812 cycles to failure
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Chemical resistance: Unaffected by most acids, alkalies,
solvents, dilute sulfuric acid (with
exception of hydrofluoric acid and
corrosive environments at elevated
temperatures).
Thermal insulation: Thermal conductivity is less than
one-half that of asbestos. The
thermal conductivity or K-value for
ZETEX 1200 is 0.3385.
Leachable chlorides: Less than 0.5 parts per million.
PERFORMANCE
Specific gravity: 2.54
Breaking strength of fabric: 350 to 500 Ibs/inch
Tensile modulus for fiber: 10.5 x 106
Coefficient of linear expansion: 2.8 x 106
Specific heat for fiber at 72°F: 0.197
RESULTS OF TESTING
Physical testing conducted in accordance with the appropriate
ASTM standard.
The leachable chlorides were done according to military
standards MIL-1-24244.
PERFORMANCE STANDARDS
Various military and government specifications are written
for asbestos.
RESEARCH AND DEVELOPMENT
Is required in the areas of fiber and finishes.
ECONOMIC INFORMATION
a. No process changes required that we know of.
b. Production costs of using ZETEX are almost identical to
those of asbestos except in the safety garment field where
they may be higher by about 20%.
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c. Costs in use: the price of ZETEX fabrics is about $5.00
to $16.00 per sq/yd to distributors and $7.00 to $22.00
per sq/yd to the end user.
d. If the government chose to restrict the use of asbestos
the increased production of ZETEX would cause a decrease
in prices of ZETEX products by up to 30%.
e. Depending on application and use, the lifetime cost of
using ZETEX products can be lower than asbestos. In
safety products* such as gloves and mittens, the cost
may be 60 - 80% higher than asbestos products.
HEALTH INFORMATION
Transient mechanical irritation
MANUFACTURER'S CONTACT
Mr. David Moore
Newtex Industries, Inc.
P.O. Box 25
Victor, New York 14564
(716) 924-9135
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COMPANY NAME Scan-Pac Manufacturing Company
9950 N. Port Washington Rd.
Mequon, Wisconsin 53092
PRODUCT NAME Complete line of nonasbestos friction materials for clutches
and brakes of all types.
TECHNICAL CHARACTERISTICS
Applications
Scan-Pac has available and is selling nonasbestos friction materials
for a myriad of uses, some of which are:
Garage door openers Winches
Lawn mower clutches Cranes
Rider mower brakes and clutches Shovels
Snowmobiles Presses
Paper machines Trucks
Wire rope machinery Fork lifts
Fishing reels Buses
Snowthrowers Industrial clutches
Medical equipment Electric motors
Machine tools Hoists
Physical Properties
Content; Depends on compound and see Health Information.
Fiber Shape and Size; Chopped glass fibers of approximately
13 microns diameter.
Dielectric Characteristics; Not applicable.
Strength; Excellent, but varies with compound.
Flexibility; Some compounds flexible, some rigid.
Resistance to Abrasion; Excellent.
Resistance to Corrosion; Not applicable.
Noise; Very quiet brake.
Moisture Absorption; Virtually none.
Performance
Specific Gravity; Varies by compound from 1.7 to 2.6.
Tensile Strength; Varies by compound; typical 2400-5000.
Coef. of Friction; Varies by compound from 0.12 to 0.60.
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Results iof Testing
All products Chase machine tested per SAE J 661 (see reference 1
and 2 under Bibliographic Information for method of testing and test results).
Performance Standards
Five truck block formulas are certified by American Association of
Motor Vehicle Administrators.
Research and Development
Most of the research and development has been done. Dry mix and
Wet mix materials research started in 1976 and is still continuing. Product
line information can be found in references 1 and 2 under Bibliographic
Information. Additional R&D on these items requires more equipment such as
dynamometers, experimental molds, experimental grinders. R&D to complete the
line has been underway for about 1 year. This includes conversion of all
asbestos items to nonasbestos shown in reference 3 of the Bibliographic
Information.
ECONOMIC INFORMATION
Costs in Production
The costs of nonasbestos process changes to users is basically the
cost of new molds. The cost to Scan-Pac is molds, changes in existing equip-
ment and/or new equipment. In both instances cost is dependent upon size of
finished parts.
Scan-Pac's production costs are somewhat higher due to nature of
components. We estimate 10 to 20 percent.
Costs in Use
Due to the vastly different sizes of finished parts (see Technical
Characteristics) and the number of different materials (see Appendix A, B,
and C), it is impossible to assign prices per ton, foot, etc.
We estimate that 20 to 35 percent premium over asbestos product is
realistic.
It is doubtful that a government ban on asbestos would lower this
percentage, as all components of nonasbestos friction materials are normally
produced for other applications.
The lifetime cost of using the nonasbestos product should be lower
than asbestos, due to elimination of precautions that must be taken when
installing or replacing asbestos. In addition, nonasbestos friction provides
.longer lining life plus less wear on mating parts.
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HEALTH INFORMATION
Scan-Pac's nonasbestos compounds do not contain any materials on Toxic
Substance Control list. The raw materials are basically the same found in
asbestos friction materials, with deletion of asbestos fiber, and addition
of chopped strand glass fiber. The size of the glass fiber (13 micron diam-
eter) is such that it cannot be respired into the human lung.
Scan-Pac's nonasbestos line can fulfill many needs that many asbestos
compounds cannot, such as:
1. Longer lining life
2. Less wear on mating surfaces
3. Full range of friction characteristics
We do not know of situations where our materials are not adequate.
BIBLIOGRAPHIC INFOBMAIION
The following references are available from the manufacturer:
1. Scan-Pac Nonasbestos Industrial Friction Materials
2. Scan-Pac Nonasbestos Truck Blocks
3. Scan-Pac Friction Materials
MANUFACTURER'S CONTACT
Paul Vandenberg
Scan-Pac Manufacturing, Inc.
9950 North Port Washington Road
Mequon, Wisconsin 53092
277
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SCOPE OF THE HEALTH WORKSHOP
by
James N. Rowe, Ph.D
U.S. Environmental Protection Agency
Washington, D.C.
It is my privilege to welcome you to the National Workshop on Health As-
pects of Asbestos Substitutes, sponsored by the Environmental Protection Agency
(EPA) and the Consumer Product Safety Commission (CPSC). It is appropriate
that we dedicate this workshop to the memory of the late Dr. Mearl Stanton of
the National Cancer Institute. Dr. Stanton*s invaluable contributions to our
understanding of the mechanisms of fiber carcinogenesis provide a scientific
basis for the rational design of safe asbestos-substitute products.
This workshop provides a forum for discussion of the potential hazards of
substitutes, study of the relevant issues, and productive communication among
the various segments of the scientific community represented here, including
industry, academia, public interest groups, and government. Our work here
should provide the regulatory agencies with helpful guidance for dealing with
the substitutes issues.
Asbestos substitutes raise complex health issues. This complexity has at
least four sources: 1) the diversity, and even the definition, of asbestos-
substitutes, 2) our incomplete understanding of the toxicology and pharmacoki-
netics of fiber and non-fiber particulates, 3) the limited development of ade-
quate scientific criteria for determining toxicities due to factors 1 and 2,
and 4) the uncertainty involved in the assessment of quantitative risk to humans
by extrapolation from toxicological data in other species.
I will briefly comment on each of these factors.
The first health related factor is the diversity and definition of asbestos
substitutes.
Asbestos substitutes deal with a wide variety of materials which may be
simplistically labeled fibrous and non-fibrous. Within each category, there
are natural and synthetic substances, each having different physico-chemical
composition, morphological characteristics, and potential for undesirable and
possibly toxic contamination. The workshop agenda illustrates this point and
suggests that the term "asbestos substitute" is open to a variety of interpre-
tations.
279
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The second factor is our limited understanding of the toxicology and
phannacokinetics of fiber and non-fiber particulates.
For example, are short, thin durable fibers (<5 vim length) completely
non-toxic and only thin durable fibers (>5 vim length) toxic or is there a
gradual transition from the ineffective fiber size to a length which possesses
maximum fiber toxicity as hypothesized by Pott1? The questions concerning the
nature of fiber-induced carcinogenicity and fibrosis and the regulatory deci-
sions made on these issues have significant impact on a very large segment of
the industrial community including the mineral and chemical industries. Dr.
Stanton's observations are critical for proper evaluation of the fibrous sub-
stitutes. His work establishes the in situ potential of a variety of chemi-
cally dissimilar, durable fibers to produce mesotheliomas in experimental
animals. However, the relationship of intrapleurally produced cancers to
carcinogenesis produced by inhalation remains to be established. In inhala-
tion of particles the lungs normal physiological barriers are involved as well
as the ultimate biodisposition of the fibers. In addition, the role of co-
carcinogens in fiber and particulate toxicology remains to be further defined.
The third factor is the need for reasonable scientific criteria for eval-
uation of asbestos substitutes.
Because of our limited understanding of the mechanisms of fiber and non-
fiber induced chronic toxicity, appropriate testing batteries or scientific
criteria can, at best, provide only a rough approximation of the hazard. In a
1974 editorial on fiber carcinogenesis2 Dr. Stanton noted that, "Our present
systems of assessing carcinogenicity in animals can at best only detect re-
sponse to large numbers of fibers; therefore, materials containing only a few
exceptionally fine fibers could easily escape detection as a hazard in simply
designed animal tests. Even with the most sophisticated test, it would be
difficult to establish an absolute threshold of safety, since each small ex-
posure possibly adds to the total hazard and represents a finite, albeit small,
ultimate risk." It behooves us to understand the state-of-art for evaluation
of substitutes and to develop scientific criteria which most accurately reflect
that understanding. This workshop should provide use with information on the
health hazards of asbestos substitutes and some thoughts on defining our
approach to evaluating substitutes.
Finally we come to the issue of quantitative risk assessment in humans.
The last factor relates to the extrapolation of in vivo and in vitro data
to humans in environmental exposure situations, i.e., quantitative risk assess-
ment. Many scientific issues remain to be settled. Evaluation of the risk to
humans remains a necessary but oftentimes difficult function for regulatory
agencies. However, quantitative risk assessment for a material with abundant
human data such as asbestos is much less ambiguous since the extrapolation does
not require interspecies comparisons between animals and man. This "luxury"
of scientific data will not be available for many substitute materials.
In conclusion, the EPA and CPSC recognize the complexity of the scientific
and health issues related to asbestos substitutes. However, we also recognize
280
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the definite health hazards which may be posed by significant exposure to as-
bestos, and the need to reduce such exposure where possible. It is therefore
important that the potential health hazards of substitutes and the limitations
of testing information be clearly defined. Such understanding will allow the
development and application of scientific policy which is both coherent and
equitable. Such progress should prevent reoccurrence of the tragic disease
manifestations which have occurred and are occurring since the introduction of
asbestos into American commerce in the 1890's.
I am very pleased by your willingness to participate in this workshop, and
I am confident that our efforts will be productive.
REFERENCES
1. Pott, F. Staub-Reinhalt Luft 38(12):486-490. 1978.
2. Stanton, M. J. Nat. Can. Inst. 59(3):633-634. 1974.
281
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INHALATION, DEPOSITION AND CLEARANCE OF PARTICLES
by
Morton Lippmann, Ph.D.
New York University Institute of Environmental Medicine
New York, NY, 10016
ABSTRACT
Inhaled particles can deposit at airway surfaces all along the respiratory
tract. For compact particles with diameters >!s urn and for fibers with
diameters £0.2 ym the probabilities of deposition at specific sites, within
specific anatomic regions, and for the respiratory tract as a whole depends
upon their aerodynamic diameters and for fibrous particles, on their lengths
as well. The fate of deposited particles, and their abilities to induce or
exacerbate toxic effects depends critically upon their deposition sites, their
cytotoxicities, their clearance pathways, their storage sites and their chemical
and physical properties.
This discussion focuses on those properties of asbestos substitutes which are
critical in determining their airborne size distributions, respiratory tract
deposition probabilities, deposition patterns within the airways, reactions
with epithelial cells and macrophages, and their toxic effects. Knowledge of
these factors may permit modifications in production specifications and trade
utilization of the products in ways which may minimize the potential for toxic
effects in the utilization of asbestos substitutes.
The major component regions of the respiratory tract differ markedly in struc-
ture, size, function, and sensitivity or reactivity to deposited particles.
Thus, a complete determination of dose from an inhaled aerosol depends on
(1) the regional deposition, (2) the retention times at the deposition sites
and along the elimination pathways, and (3) the physical, chemical, and bio-
logical properties of the particles. Here, we will discuss first the factors
that determine the amounts and patterns of particle deposition within the com-
ponent regions of the respiratory tract and then the pathways and dynamics of
particle translocation and elimination. Both discussions will emphasize the
normal patterns of behavior and transport applicable to particles that are not
acutely toxic, but may produce chronic lung disease after extended periods of
inhalation exposure.
283
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FUNCTIONAL ZONES FOR PARTICLE DEPOSITION
The respiratory tract (Figure 1) can be divided into zones on the basis
that insoluble particles that deposit in each zone contact or affect different
cell populations and/or have substantially different retention times and clear-
ance pathways. Each zone includes one or more anatomic regions. The clearance
kinetics for particles deposited in each zone will be discussed in greater
detail under Particle Retention.
Particles deposited in the unciliated anterior portion of the nose remain
at the deposition sites for a variable and ususally indeterminate time—that is,
until they are removed mechanically by nose wiping or blowing, sneezing, etc.
After leaving the nares or nostrils, the inspired air passes through a web of
nasal hairs and flows through the narrow passages around the turbinates. It
is warmed, and moistened, and is partially depleted of particles with aero-
dynamic diameters larger than 1 ym by impaction on the nasal hairs, at bends
in the air path, and by sedimentation. Particles smaller than 0.1 ym can
deposit in this zone by diffusion. The surfaces are covered by mucus. Most
of the mucus in this region is propelled toward the pharynx by the beating of
the cilia, carrying with it deposited insoluble particles. Soluble particles
may be dissolved in the mucus. Some mucus moves toward the anterior nares,
carrying inhaled whole or dissolved particles into the zone of intermittent
mechanical clearance.
Particles inhaled through the nose and deposited in the nasopharynx, or
particles inhaled through the mouth and deposited in the mouth and oropharynx,
are swallowed within minutes. They pass through the esophagus in or on the
mucus coming up from the trachea.
The tracheobronchial or conductive airways have the appearance of an
inverted tree, with the trachea analogous to the trunk and the subdividing
bronchi to the limbs. The airway diameter decreases distally, but because of
the increasing number of tubes the total cross section for flow increases and
the air velocity decreases. In the larger airways, particles too large to
follow the bends in the air path are deposited by impaction. At the low veloc-
ities in the smaller airways, particles deposit by sedimentation and diffusion.
Ciliated and secretory cells are found at all levels. Inert, nonsoluble parti-
cles deposited in normal ciliated airways are cleared within 1 day via the
larynx on the moving mucus.1
The zone beyond the ciliated airways is where gas exchange takes place.
The epithelium is very thin, and soluble particles are believed to enter the
pulmonary blood within minutes. Insoluble particles deposited in this zone
by sedimentation and diffusion are removed very slowly with clearance half-
times of days, months, or years. The mechanisms for clearing insoluble parti-
cles from the alveolar zone are only partly understood, and their relative
importance is a matter of some debate, as discussed under Alveolar Clearance.
FACTORS AFFECTING PARTICLE DEPOSITION
Particles deposit in the various zones or regions of the respiratory tract
by a variety of physical mechanisms. Deposition efficiency in each region
2S4
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OLFACTORY AREA
CONCHAE
VESTIBULE
TRACHEA. 20mm
LUNG
BRONCHUS 8mm
PULMONARY
ARTERY
LYMPHATICS
PULMONARY
VEIN
LYMPHATICS
NASOPHARYNX
ORAL PHARYNX
EPIGLOTTIS
LARYNX
BRONCHIAL
ARTERY
LUNG LOBULE
LUNG
TRACHEO- BRONCHIAL
LYMPH NODES
0.5 TO 1.5 cm
CONDUCTING
BRONCHIOLE, 0.6mm
TERMINAL
BRONCHIOLE, 0.6mm
RESPIRATORY
BRONCHIOLE, 0.5mm
ALVEOLAR
DUCT, 0.2mm
ALVEOLAR
SAC, 0.3 mm
ALVEOLUS
Figure 1. Structure of the respiratory tract,
285
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depends on the aerodynamic properties of the particles, the anatomy of the
airways, and the geometric and temporal patterns of flow through them.
Deposition Mechanisms
Significant particle deposition can occur within the respiratory tract by
five mechanisms: interception, impaction, sedimentation, diffusion, and elec-
trostatic precipitation. However, in most cases, only impaction, sedimentation
and diffusion will be important.
Interception—
Interception usually is significant only for fibrous particles. It takes
place when the trajectory of a particle brings it close enough to a surface so
that an edge contacts the surface; thus the particle size must be a significant
fraction of the airway diameter. Fibers 200 ym long have been observed in
human lung samples.2 Straight fibers, such as amphibole asbestos, are more
likely to penetrate to the alveoli than similarly sized, but curly, chrysotile
asbestos because the straight fibers assume orientations more parallel to the
flow streamlines.
Impaction—
Inhaled air follows a tortuous path through the nose or mouth and branching
airways in the lung. Each time the air changes direction, the momentum of parti-
cles tends to keep them on their preestablished trajectories, which can cause
them to impact on airway surfaces. The most likely deposition sites are at or
near the carinas of the large airway bifurcations.
S ediment at ion—
Gravitational sedimentation is an important mechanism for deposition in
the smaller bronchi, the bronchioles and the alveolar spaces where the airways
are small and the air velocity is low. Sedimentation becomes less effective
than diffusion when the terminal settling velocity of the particles falls below
approximately 0.001 cm/sec, which for unit-density spheres is equivalent to a
diameter of about 0.5 ym.
Diffusion—
Submicrometer particles in air move randomly under the impact of gas mole-
cules. This Brownian motion increases with decreasing particle size. It
becomes an effective mechanism for particle deposition in the lung as the root-
mean-square displacement approaches the size of the air spaces. Diffusional
deposition is important in small airways and alveoli and at airway bifurcations
for particles smaller than about 0.5 jam. For radon and thoron daughters, where
the particle size is molecular, diffusional deposition efficiency can be high
in the head and in large airways such as the trachea.
Electrostatic Precipitation—
Particles with electric mobility can have enhanced deposition in the
respiratory tract even though no external field is applied across the chest.
Deposition results from the image charges Induced on the surface of the airways
by the charged particles. Test aerosols resulting from the evaporation of
aqueous dgoplets can have substantial mobilities, and the results of some exper-
imental deposition studies using such aerosols without charge neutralization
are accordingly suspect. Freshly fractured mineral dust particles may also be
highly charged. 286
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Aerosol Factors
Particle size is always an important variable in regional deposition.
There are a number of ways of expressing particle size. In this discussion,
and in most health-related literature, particle size is expressed in terms of
actual or equivalent diameters. When particle size is measured by one param-
eter and expressed in terms of another or equivalent size, the basis for the
conversion must be clearly established. Nonspherical particles are frequently
characterized in terms of equivalent spheres, for example, on the basis of
equal volumes, equal masses, or aerodynamic drag. A parameter in increasingly
common use is aerodynamic diameter (D), which incorporates both particle
density and drag.
Aerodynamic diameter is the most appropriate parameter in terms of parti-
cle deposition by impaction and sedimentation, which usually account for most
of the deposition by mass in the head and lungs. On the other hand, diffusional
displacement, which is the dominant mechanism for particles smaller than % um,
depends only on particle size and not on density or shape. Interception also
depends on the linear dimensions of the particle, as well as its shape, since
aerodynamic drag can affect the particle's orientation within the airway.
Respiratory and Flow Factors
An important respiratory factor already discussed as a parameter affecting
deposition is air velocity. Increasing velocity increases Impaction deposition,
but decreases sedimentation and diffusion by decreasing residence time. The
flow is cyclical and reverses many times per minute. At its peak, flow may be
turbulent in the trachea, but the Reynolds number decreases with increasing
lung depth, so that in the smaller conducting airways flow is always laminar,
and in the alveolar region it is always viscous.3
Since flow is laminar in most of the anatomical dead space, the core
velocity is almost twice the average velocity. Thus, even in very shallow
breathing, a substantial fraction of the inhaled air penetrates beyond the
anatomical dead space, and particles with appreciable sedimentation rates (e.g.,
particles larger than 2 um) or large diffusional displacements (e.g., particles
smaller than 0.1 um) can deposit efficiently in peripheral airways.
The tidal volume is an important respiratory parameter. The air inhaled
at the start of each breath goes deeper into the lung and remains there longer
than the air inhaled later in the breath. The deeper the air goes and the
longer it stays, the greater the depletion of inhaled particles. Thus, for
quiescent breathing—where the air velocity is low, mixing is minimal, and the
tidal volume is only two to three times the dead-space volume—a large propor-
tion of the inhaled particles can be exhaled. Conversely, for heavy exertion,
where larger volumes are Inhaled at higher velocities, both impaction in the
large airways and sedimentation and diffusion in the smaller airways and
alveoli will be greater.
287
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Anatomical Factors
Intrasubject variations in airway anatomy affect particle deposition in
several ways: (1) the diameter of the airway influences the displacement
required by the particle before it contacts the airway surface; (2) the cross
section of the airway determines the flow velocity for a given volumetric flow
rate; and (3) variations in diameter and branching patterns along the bronchial
tree affect the mixing characteristics between the tidal and reserve air in the
lungs. For particles with aerodynamic diameters below 2 urn, such convective
mixing can be the single most important determinant of deposition efficiency.
There are also significant intersubject differences in respiratory tract
anatomy. For example, the average alveolar-zone airspace dimension has a sub-
stantial coefficient of variation when measured either post-mortem on lung
sections or in vivo by aerosol persistence during breath holding. In the
former case, Matsuba and Thurlbeck*1 reported a mean size and variation of
0.678 mm ± 0.236. In the latter case, Lapp, et al. ,5 found values of 0.535 mm
± 0.211.
Physiological Factors
In regard to physiological factors, the effective diameters of the conduc-
tive airways for airflow are defined by the surfaces of the mucous layers. In
normals, the mucuous layer on the larger conductive airways is believed to be
only about 5 ym thick6 and decreases with airway size. In terminal bronchioles,
it may be only 0.1 ym thick.7 Hence, the reduction in air-path cross section
by the mucous is negligible. On the other hand, in individuals with bronchitis,
the mucous layer can be much thicker, and in some locations it can build up and
partially or completely occlude the airway. Air flowing through partially
occluded airways will form jets, which will probably cause increased deposition
of particles in small airways by impaction and turbulent diffusion.
Other Effects
No discussion of the deposition of inhaled aerosols would be complete with-
out consideration of the influence of airborne contaminants on the lungs of the
people inhaling the particles. Inhaled irritants can affect the fate and tox-
icity of the inhaled particles by altering airway caliber, respiratory function,
clearance function, and/or the function, survival, and distribution of the cells
which line the airways. Any reduction in cross section in the larger bronchial
airways increases flow velocities and should, therefore, increase particle depo-
sition by impaction. Tracheobronchial particle deposition is significantly
greater in cigarette smokers than in nonsmokers,8» »x° presumably because of
the bronchoconstrictive properties of cigarette smoke.
While some normal cigarette smokers have increased bronchial deposition,
the increase is relatively small compared to that in individuals with clinically
defined, chronic bronchitis.8*11'12 Greatly increased tracheobronchial parti-
cle deposition has also been seen in some asymptomatic asthmatics.8
288
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EXPERIMENTAL DEPOSITION DATA
Total Deposition
Relatively few attempts have been made to measure regional particle deposi-
tion in humans. A much larger number of studies have explored total deposition.
For particles between 0.1 and 2 ym aerodynamic diameter, deposition in the con-
ductive airways is generally very small in comparison to deposition in the
alveolar regions, and total deposition approaches alveolar deposition. Total
deposition as a function of particle size and respiratory parameters has been
measured experimentally by numerous investigators. Many previous reviews of
deposition have called attention to the very large difference in the reported
results.13'17
Much of the discrepancy can be attributed to uncontrolled experimental
variables and poor experimental technique. The major sources of error have
been described by Davies.3 Data from studies performed with good techniques
and precision all appear to show the same trend, with minimum deposition at
about 0.5 ym diameter.
The deposition data in Figure 2 by Chan and Lippmann18 and Stahlhofen, et
al.,19 were based on external in vivo-measurements of y~tagged particle reten-
tion. This technique was also used by Swift, et al.20 for tests in the 0.03 ym
size range.
Head Deposition
Some inhaled particles deposit within the air passages between the point
of entry at the lips or nares and the larynx. The fraction depositing can be
highly variable, depending on the route of entry, the particles' sizes, and
the flow rates. In most cases, the nasal route is a more efficient particle
filter than the oral, especially at low and moderate flow rates. Thus, people
who normally breath part or all of the time through the mouth may be expected
to deposit more particles in their lungs than those who breathe entirely through
the nose. During exertion, the flow resistance of the nasal passages causes a
shift to mouth breathing in almost all people.
Deposition in the Tracheobronchial Zone
Figure 3 shows in vivo measurements of tracheobronchial (T-B) deposition
of normal healthy humans by Lippmann and co-workers,8»15*18»21»22 and Stahl-
hofen, et al.19 T-B deposition for a given particle size varies greatly from
subject to subject among nonsmokers, cigarette smokers and patients with lung
disease.18 Average T-B deposition is slightly elevated in smokers and greatly
elevated in the lung-disease patients.8'1 However, among normals and non-
bronchitic smokers, each individual has a characteristic and reproducible rela-
tionship between particle size and deposition. T-B deposition includes both
deposition by impaction in the larger airways and deposition by sedimentation
in the smaller airways. Impaction deposition predominates for large particles
(diameter larger than 3 ym) and high flow rates (more than 20 L/min), while
sedimentation deposition becomes a larger fraction of a diminishing T-B com-
ponent for smaller particles and lower flows.
289
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1.0
0.8
•35 0.6
o
O.
a>
0.2
0
_ O
Experimental Doto
Chan and Lippmann
Swift.etal
Stahlhofen.etal
\
\
Predictive Models
Yu
Davies.etai
Heyder.etai
0.01 0.05 0.1 - 05 1 5 10 20
Mass Median Diameter /im >< Aerodynamic Diameter p.m
Figure 2. Experimental total respiratory tract deposition data
from radioaerosol studies, and predictive models for
total deposition.
290
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1.0
0.8
:! 0.6
o
o>
03
0.4
0.2
0
Lippmann
Chan and Lippmann
Stahlhofen, et a[
n
0.01 0.05 Ql
Mass Median Diameter
0.5 I 5 10 20
-*f— Aerodynamic Diameter /im
Figure 3. Experimental tracheobronchial (T-B)
data for radioaerosol studies.
291
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For deposition within the tracheobronchial zone, the pattern of deposi-
tion within hollow airway casts made from normal human lungs demonstrates
the airway bifurcations accumulate a disproportionate share of the deposits. »
Furthermore, the density of the surface deposition on the bifurcation regions
appears to correspond close with the incidence of primary cancer sites. The
largest numbers of human lung cancers are found in lobar bronchi. Among the
lobar bronchi, the largest numbers are found at the right upper bronchus and
the smallest in the right middle bronchus. Figure 4 shows cast deposition data
for the lobar bronchi for various particle sizes and flow rates. While the
absolute amounts of deposition vary considerably with particle size and flow
rate, the relative amounts on the various lobar bronchi remain relatively con-
stant and appear to be closely associated with the cancer incidence reported
in the pathological literature.
Figure 5 shows alveolar deposition values obtained in mouth-breathing
inhalation tests on nonsmoking normals. These data are based on external
measurements of the retention of y~tagged particles after the completion of
the bronchial clearance. It can be seen that the data of Chan and Lippmann18
and Stahlhofen, et al. ,19 are in good agreement, and both sets of data appear
to be consistent with the earlier data of Lippmann and Altshuler.22
Figure 6 shows an estimate of the alveolar deposition that could be
expected when the aerosol is inhaled through the nose. The estimate is based
on the difference in head retention during nose-breathing and mouth-breathing
from the analysis of Lippman.15 It can be seen that for mouth-breathing, the
size for maximum deposition is about 3.5 ym, and that about half of the
inhaled aerosol of this size deposits in this region. For nose-breathing,
there is a much less pronounced maximum of about 25 percent at 2.5 urn, with a
nearly constant alveolar deposition averaging about 20 percent for all sizes
between 0.1 and 4 um.
Figure 6 also shows the sampler acceptance criteria of the British Medical
Research Council (BMRC) and of the American Conference of Governmental Industrial
Hygienists (ACGIH). These criteria define the cutoff characteristics of the
precoHectors preceding respirable dust samplers. It can be seen that both
provide reasonable approximations of the cutoff characteristics of the human
conductive airways, at least those of nonsmoking normals. The alveolar deposi-
tion calculated on the basis of the International Commission on Radiological
Protection (ICRP) Task Group's model17 departs significantly from the deposi-
tion observed in reliable experimental studies.
The 1966 Task Group report has been widely quoted and used within the health
physics field. One of the significant conclusions of the Task Group study was
that regional deposition within the respiratory tract can be estimated using a
single aerosol parameter, the mass median diameter. For a tidal volume of
1450 cm3, there were relatively small differences in estimated deposition over
a very wide range of geometric standard deviations (1.2
-------
301pm
60
£50
o
|40
I30
'I 20
Right Upper
10
0
g
Right Middle
Right Lower
**.&
Left Upper Left Lower
I
Aerodynamic Diameter of Test Aerosol and Reported Cancer Incidence
Figure 4. Percentage of total particle deposition within
the five lobar bronchi of the cast which occurs
within each lobar bronchus, at a flow rate of
30 L/min, compared with the reported percentage
of total lobar bronchial carcinomas which
originate within each lobar bronchus. Data on
cancer sites are from Schlesinger and Lippman.2**
With permission of Academic Press.
293
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1.0
0.8
o 0.6
Q
5 0.4
o
^ 0.2
1 1 1 1
Experimental Doto Predictive Models
• Chan and Lippmann — Yu
o Stahlhofen.ctd ICRP,750ml(1966)
—— Lippmann and Altshuler
T T
0.01 0.05 0.1 0.5
Mass Median Diameter /im
I 5 10 20
Aerodynamic Diameter
Figure 5. Alveolar deposition data from radioaerosol
inhalation studies, and predictive models
for alveolar deposition.
294
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1.0
0.8
0.6
J
"J75
0.4
0.2
Task Group Model (TSOcc)
Sampler Acceptance
Criteria
IMRC
0.1 0.2 0.5 1.0 2 5 10 20
Aerodynamic Diameter (//m)
Figure 6. Comparison of sampler acceptance curves
of BMRC and AC6IH with alveolar deposition
according to an ICRP Task Group,17 and
from the experimental New York University
deposition data of Figure 5.
295
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individual, rates of clearance vary greatly from region to region within the
respiratory tract. This variation was a major basis for the characterization
of functional zones described earlier. In two of these zones—the ciliated
nasal passages and the tracheobronchial tree-clearance in normal individuals
is completed in less than 1 day. In the alveolar zone, clearance proceeds by
slower processes, most of which vary considerably with the composition of the
particles. A detailed discussion of alveolar clearance will follow the dis-
cussion of mucociliary clearance.
CLEARANCE OF PARTICLES FROM THE CONDUCTING AIRWAYS
Particles that deposit in the airways that conduct the inspired air to
the respiratory tissue may be cleared by several mechanisms. The most impor-
tant mechanism for insoluble particles is mucociliary clearance. Particles
deposited on the surface of the mucous are transported proximally as the mucous
is propelled by the rhythmic beating of the cilia. However, soluble particu-
lates, depending on their physicochemical properties, may either be incorporated
into the mucous, be taken up by the airway epithelium, or pass through the
epithelium to be cleared by the bronchial and pulmonary circulations. It has
been suggested that some insoluble particles may penetrate the mucous and enter
epithelial cells.25 Conversely, it has been postulated that particles from
interstitial spaces and lymphatics may enter the airway lumen and be removed
subsequently by mucociliary activity. '27 A recent review by Wanner emphasizes
the clinical aspects of mucociliary transport.28 This review will concentrate
on the role of mucociliary transport in the normal lung as a defense mechanism
through its clearance of inhaled particles.
Stationary collimated scintillation detectors can be used to obtain mea-
surements of thoracic particle retention which are essentially independent of
the particle distribution within the thorax.8'19 Figure 7 shows particle reten-
tion curves for inert, insoluble tagged monodisperse particles in the hours
following a 1 minute inhalation exposure for four different nonsmoking, healthy
human males. It can be seen that clearance rates vary widely, even when the
amounts cleared are comparable. On the other hand, clearance rates are quite
reproducible in a given individual when the same particle size is inhaled, and
they vary systematically with changes in particle size and the concomitant
changes in deposition pattern (Figure 8).
It is clear that there is a wide variation in the rate at which seemingly
healthy individuals clear deposited radioaerosols from the lungs. In persons
with chronic obstructive pulmonary disease, there is a somewhat wider varia-
tion. However, the within-subject variation is greatly increased.29 This
suggests that loss of control of mucociliary transport could cause and/or
result from chronic obstructive lung disease.
FACTORS AFFECTING MUCOCILIARY TRANSPORT
Cigarette Smoke
The studies reporting effects of.smoking on mucociliary transport have been
very confusing because of the widely varying effects that tobacco smoke produces.30
296
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100
SUBJECT i 6
TEST 162 A
PARTICLE SIZE < 4.1
0
39
80A
2.3
1 03
77T I55T
3.7 3.4
e e
to
vo
S 6 7
TIME - HOURS
Figure 7. Retention of ytagged, monodisperse ferric oxide microspheres as a
function of time following a 1-minute inhalation exposure via
mouthpiece, for four healthy nonsmoking males.
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Subject 65
Test
0 » 0 * I
138A 116A 116T 119A 138T 119T
Size 1.8 1.7 3.3 4.2 5.8 6.0
NJ
VO
00
12 * 1 day
Figure 8. Retention of y-tagged monodisperse ferric oxide
microspheres of various particle sizes for a
single nonsmoking male participating in a series
of inhalation tests. The fraction of the inhaled
particles cleared by mucociliary clearance varies
systematically with particle size, but the
effective duration of the bronchial clearance
phase is relatively independent of size. With
permission from the American Medical Association.
-------
In man, the immediate response to normal smoking has been either an increase
in tracheobronchial clearance, or no effect.31*'2'33 In the donkey, low expo-
sure levels of cigarette smoke accelerated clearance,31* but impairment of
clearance was observed at higher levels.31* The relative increase in transport
is greater in the small airways.35 This may be due partly to the adrenergic
stimulation caused by tobacco smoke. Chronic smoking appears to have a more
variable effect on mucociliary transport. This is due to variation in dosage,
degrees of individuals' susceptibility to tobacco smoke, the diversity of
studies undertaken, and the small number of subjects involved. Yeates, et
al.,32 have shown that tracheal transport rates were within normal limits in
nine smokers studied. Although rapid clearance has been observed in some
long-term smokers, impairment of large airway clearances has been suggested
by Albert, et al.,1 Bohning, et al.,*6 Camner, et al.,37 and Lourenco, et al.38
Pavia, et al.,39 and Thomson and Pavia11 were unable to demonstrate any effect
on of long-term smoking on bronchial clearance. Albert, et al.1 showed that
some heavy cigarette smokers had long overall bronchial clearance times,
which could be interpreted as slow clearance in small airways. Faster clear-
ance has been observed in smokers studied three months after cessation of
smoking.1*0 Chronic high-level exposure to cigarette smoke has been found to
severly impair bronchial clearance in the donkey,1*1 with recovery almost
complete within a few weeks after cessation of smoking.
Sulfur Oxides
In vivo exposures to sulfur dioxide at concentrations that have been
measured in ambient air are not likely to affect mucociliary clearance. At
higher levels, more typical of some occupational exposures, effects have been
observed. Wolff, et al.,1*2 exposed nine nonsmokers to 5 ppm (13 mg/m3) of
802 for three hours after an albumin aerosol tagged with 99Tc. The tracheo-
bronchial mucociliary clearance of the tagged aerosol was essentially the
same as in control tests, except for a transient acceleration at one hour
after the start of the S02 exposure. In further tests by Wolff, et al.,1*3
it was shown that exercise accelerates bronchial clearance, and 5 ppm of 802
during exercise speeds clearance significantly beyond that produced by the
exercise alone.
High concentrations of S02 can slow bronchial clearance. In donkeys,
thirty-minute exposures to 802 via nasal catheters produced delayed bronchial
clearance and severe coughing and mucus discharge via the nose when the con-
centration exceeded 300 ppm. ^** Mean residence times following exposures of
53 to 300 ppm were not significantly different from control levels. The one
test performed at a lower concentration (27 ppm) produced an acceleration in
bronchial clearance, which would be consistent with the clearance accelera-
tions seen by Wolff et al.,85'98 with 5 ppm exposures. These results—an
acceleration at low concentrations and a slowing at higher levels of exposure—
are similar to those produced by cigarette smoke.
Fairchild, et al.1*5 showed that four-hour exposures to high concentrations
of sulfuric acid (15 mg/m3 of 3.2 ym CMD droplets) reduced the rate of ciliary
clearance of a tagged streptococcal aerosol from the lungs and noses of mice.
At concentrations of 1.5 mg/m3 of 0.6 ym CMD droplets, there were no signifi-
cant effects.
299
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Schlesinger, Lippmann, and Albert46 demonstrated that one-hour exposures
to submicrometer sulfuric acid mist at concentrations in the range of 200 to
1000 ymg/m3 produced transient slowings of bronchial mucociliary particle
clearance in three of four donkeys tested. In addition, two of the four
animals developed persistently slowed clearance after about six acid aerosol
exposures. Similar acid exposures had no effects on regional particle depo-
sition or respiratory mechanics, and corresponding exposures to ammonium sul-
fate had no measurable effects. In subsequent tests, the two animals showing
only transient responses, and two previously unexposed animals, were exposed
one hour daily five days per week, to submicrometer sulfuric acid mist at
100 yg/m3.47 Within the first few weeks of exposure, all four animals devel-
oped erratic clearance rates, i.e., rates that on specific test days were
either significantly slower than or significantly faster than those in their
preexposure period. However, the degree and the direction of change in rate
differed to some extent in the different animals. The two previously unex-
posed animals developed persistently slowed bronchial clearance during the
second three months of exposure and during four months of follow-up clearance
measurements, while the two previously exposed animals adapted to the exposures
in the sense that their clearance times fell consistently within the normal
range after the first few weeks of exposure.
The sustained, progressive slowing of clearance observed in two initially
healthy and previously unexposed animals is a significant observation, since
any persistent alteration of normal mucociliary clearance can have important
pathological implications.
Short-term inhalation exposures of healthy human volunteers to sulfuric
acid mist produced consistent results. Ten healthy nonsmokers inhaled
0.5 urn (a = 1.9) HaSOt, at 0 (control), 110, 330, and 980 yg/m3 for one hour
via nasal mask in random sequence on four separate days. Respiratory mechani-
cal function was assessed before and %, 2 and 4 hrs after the HaSOtf exposure.
A 99Tc tagged FeaOa aerosol (7.5 ym aerodynamic diameter, ag < 1.1) was
inhaled ~ 10 min before each I^SOi^ exposure, with flow rate = 1.0 L/s, tidal
volume = 1.0 L and respiratory rate = 15/min. Thoracic retention of the
deposited radioactivity was monitored using collimated scintillation detectors.
A tracheal probe was used to determine the tracheal mucociliary transport
rates (TMTR's) of local concentrations of activity. Bronchial mucociliary
clearance was markedly altered in a dose dependent pattern in six of the
individuals and in the group as a whole. Exposures to 110 yg/m3 resulted in
a significant acceleration in mucpciliary clearance (group mean tracheo-
bronchial clearance half-time (TB^) decreased from 80 to 50 min.) Exposures
Jx) 980 yg/m3 caused a significant transient slowing of clearance, with the
TBu increased to 118 min. In contrast, there were no significant changes in
TMTR, or in indices of ventilatory mechanics (^25» ^aw and distribution of
ventilation by N£ washout.) The four individuals whose clearance times were
not significantly affected by these I^SO^ exposures had the fastest bronchial
clearance among the ten, and they were each given an additional test with a
1,000 yg/m3 E^SOtt exposure preceding the tagged Fe£03 aerosol. Three of them
responded with threefold or greater increases in TB^. Thus, 9 of 10 subjects
had substantial changes in bronchial clearance times following
48
exposures
300
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ALVEOLAR CLEARANCE
Once a material Is deposited on the respiratory epithelium of the alveo-
lated spaces, clearance takes place by means of two general kinds of processes.
These processes can be termed absorptive and nonabsorptive. Most likely, the
processes occur together or with temporal variations.
The most widely-accepted nonabsorptive clearance mechanism in the alveolar
region is phagocytosis by macrophages.1*9 Despite the common acceptance of
phagocytosis and subsequent cell removal as the dominant nonabsorptive clear-
ance mechanism, it has, so far, not been adequately described in quantitative
terms. For example, there are conflicting data on the effect of particle size
on phagocytic uptake by rabbit alveolar macrophages. Holma50 found uptake to
decrease with particle size, while Hahn, Newton, and Bryant51 found the oppo-
site. Holma1s smallest particles were 1.5 ym, while Halm's largest were
2.2 ym. The results could be consistent if uptake peaked at 2 ym. More data
are clearly needed to clarify this issue.
The clearance pathways for phagocytosed particles remain controversial.
It is generally agreed that macrophages ingest particles and transport them
proximally on the bronchial tree to be swallowed. However, there is consider-
able disagreement on the predominant pathway between the alveoli and the
bronchial tree. There are proponents for an interstitial route, while others
favor a continuous proximally moving surface film which draws the cells onto
the ciliated surface at the terminal bronchioles.
A chronic phase of clearance, characterized by the appearance of particles
within macrophages of the connective tissue compartment of the lungs, begins
from one to three weeks after exposure, according to Sorokin and Brain.52
The extent of such sequestering of particles increases slowly in the subsequent
weeks and months. For several months, a far greater percentage of alveolar
than of connective tissue macrophages store inert particles, but ultimately
whatever remains uncleared from the lungs resides in the connective tissue.
The fate of cytotoxic particles may differ from that of relatively inert
particles.
The internal redistribution of particles retained within the lung is an
important factor in determining the site of damage. Redistribution is appar-
ent in the centrilobular accumulation of pigment seen on the cut surfaces of
human sections.53,5^,55 Such a focal accumulation of particles can also
influence their retention and pathogenic potential.
For low mass concentrations of short fibers that were neutron activated,
Morgan, Evans, and Holmes56 found no significant differences between amphibole
and chrysotile asbestos in in vivo retention in the rat. Autoradiographs of
lung sections indicated that the initial deposition was uniform right out to
the lung periphery, while over a few months the fibers accumulated in foci
that were mainly subpleural.
In subsequent experiments, Morgan, Holmes, and Talbot57 administered
radioactive asbestos to rats by inhalation. After exposure, the animals were
301
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sacrificed serially and the lungs were subjected to bronchopulmonary lavage.
Initial washes were made with a balanced salt solution that removed free
fiber and cells from the conducting airways. Subsequent washes were made
with physiological saline, which recovered cells that originally were in the
alveolar spaces. The number of cells and the amount of fiber recovered in
each wash were measured. About 20 yg of fiber was deposited in the lung and
appeared to have no significant effect on either the number or size of free
cells in the lung. Uptake of fiber by alveolar macrophages was effectively
complete after 24 hours. Analysis of the results suggests that fibers much
longer than the diameter of the alveolar macrophage (about 12 ym) find their
way into the alveolar wall from where they cannot be recovered by lavage.
This process is complete within two weeks of exposure.
Wright and Kuschner58 used short and long asbestos and manmade mineral
fibers in intratracheal instillation studies in guinea pigs. With long
fibers, all of the materials produced lung fibrosis, although the yields varied
with the materials used. However, with equal masses of short fibers of equiva-
lent fiber diameters, none of the materials produced fibrosis.
Short fibers are less damaging, it appears, because they can be fully
ingested by macrophages.59 Longer fibers can rupture the macrophage membrane,
which can result in release of digestive enzymes and/or loss in mobility.60
Most inhalation studies have been performed with aerosols containing
both short and long fibers, and it should be noted that responses may be
related primarily to the initial burden and/or persistence of the longer
fibers. For example, Middleton, Beckett, and Davis61 exposed rats to
U.I.C.C. (International Union Against Cancer) standard reference samples of
amosite, crocidolite, and chrysotile A at concentrations of 1, 5, and 10 yg/m3,
and sacrificed them serially over the next four months. They found less
retention of chrysotile than of the amphiboles, and the clearance of the
amphiboles appeared to be dose related.
TRANSLOCATION OF PARTICLES
Particles that penetrate the alveolar surface can migrate through the
lymphatic drainage system to pleural, hilar, and tracheal lymph nodes. How-
ever, the migration is very slow. Ferin62 found negligible accumulation of
titanium dioxide in the lymphatics at 25 days. Sorokin and Brain52 reported
that significant buildup of ferric oxide particles in the lymphatics did not
take place until nearly a year after the aerosol exposure. On the other hand,
Thomas63 reported that the concentration of radioactive particles in the lymph
nodes exceeds the lung concentration at several months after the end of the
inhalation. Ferin6** found that the fraction of lung dust cleared via the
lymphatics increased with total lung burden of dust.
Materials deposited by inhalation can usually be found in measurable
quantities in other organs. In most cases, the presumed pathway is the blood-
stream following'gradual dissolution in lung fluids and diffusion into pul-
monary capillaries. Absorption presumably depends on materials' being mainly
in a monomeric state or, to a lesser extent, in polymeric forms of small dimen-
sions.65 Some in vitro solubility models66'67 have proven useful in predicting
302
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in vivo clearance rates, but at other times provide inconsistent or erroneous
estimates. Further work is needed to improve these models.
ALVEOLAR CLEARANCE KINETICS
The clearance of particles deposited in the alveolar region proceeds in
several temporal phases which usually can be described by a series of expon-
entials. Each presumably corresponds to a different clearance mechanism.
68
Casarett proposed that the earliest alveolar phase, with a half-time
measured of weeks, is generally associated with phagocytic clearance, while a
slower phase, with a half-time in months or years, is generally associated with
solubility. The ICRP Task Group model17 does not include the initial alveolar
phase. Casarett attributes the omission to the task group's overreliance on
data from studies in which the phase was absent because of the cytotoxicity
of the dusts used. Jammet, et al.69 showed that for hematite dust, a clearance
phase with a half-time of 10 to 12 days is normally present in the cat, rat,
and hamster preceding a slower phase with a half-life exceeding 100 days.
The 10-to-12 day phase disappeared when the animals were exposed to sufficient
plutonium,70 silica dust, or carbon dust,71 while the half-time for the slower
phase was relatively unaffected.
Considering the recognized importance of the alveolar retention of rela-
tively insoluble particles in the pathogenesis of chronic lung disease, it is
somewhat surprising that examination of the literature yields virtually no
useful data on the rates or routes of alveolar particle clearance in man.
The only experimental studies on human alveolar clearance are those of
Albert and Arnett72 and Morrow, et al.73*71*
In the Albert and Arnett study, eight normal human males inhaled neutron
activated metallic iron particles. For three subjects, there was sufficient
residual activity after the completion of the bronchial clearance for continued
measurement of retention. For a 32-year-old nonsmoking male, and a 27-year-old
male who was a moderate smoker, the postbronchial clearance occurred in two
phases, a fast phase lasting about one month and a much slower terminal phase.
The faster phase was missing in a 38-year old, two-pack-a-day cigarette
smoking male with chronic cough. While it is not possible to draw firm
conclusions from these limited data, they are consistent with the recent
findings of Cohen, et al.,75 who studied the alveolar clearance rates of mag-
netic particles in nine nonsmokers and three smokers, using an external
magnetometer for the particle retention measurements. The clearance rates
in all three smokers were much lower than in any of the nine nonsmokers. Thus,
it appears that the fast alveolar phase can be detected in man and that ciga-
rette smoking may increase dust retention beyond the retention of the smoke
particulates themselves. Low doses of cigarette smoke have been shown to
inhibit macrophage phagocytosis.76
The only other experimental human inhalation studies of alveolar clear-
ance under controlled conditions, as noted, are those of Morrow, et al. In
an initial study,?tf these authors had four normal individuals inhale a 51fMn02
aerosol with a median size of 0.9 ym, a geometric standard deviation of 1.75,
303
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and a concentration of 4 mg/m3. The aerosol was inhaled for 20 to 30 min In
a breathing pattern in which four normal inhalations alternated with a maximal
inhalation. Measurements made more than 48 hours after the inhalation showed
a single clearance phase for all four individuals, with biological half-times
that varied only from 62 to 68 days.
In the additional human studies of Morrow, et al.,73 using several dif-
ferent aerosols, alveolar clearance rates were also reported in terms of a
single exponential. The half-times varied with the composition of the part-
icles. Half times of 65, 62. and 35 days were found for 5l*Mn02, FeaOa labeled
with 51Cr, and polystyrene 5*Cr respectively. The half-time for the polysty-
rene particles may have been relatively short because it was based on less
than 14 days of measurements and, therefore, may have been more influenced
by a rapid initial rate of alveolar clearances than were the half-times for
the iron and manganese oxides, which were followed for periods between 45
and 120 days.
ALVEOLAR RETENTION OF MINERAL DUST
The pneumoconioses are chronic lung diseases with long latent periods,
and radiographic changes and/or functional decrements that result from the
accumulation of respirable dust in the deep lung regions cannot be detected
for many years after the exposures that produced them. Furthermore, the
latent period for the pneumononioses tends to increase as the exposure level
decreases. For example, evidence for disease may appear within 15 years when
exposure levels are very high, but not for more than 30 years when exposure %
levels are much lower.
The long latent period makes it very difficult to establish causal
relationships between exposure and response, since the exposure conditions
at the time the disease is diagnosed may bear little relation to those
present earlier.
SUMMARY
Particle deposition efficiencies and patterns within the respiratory
tract are highly variable. They are determined by the air path dimensions
and configurations in the individual, the pattern and depth of the respirations,
and the characteristics of the airborne particles. The bronchial airways vary
considerably in size among normal, nonsmoking adults; these variations are
even greater among smokers without clinical disease symptoms.
The distribution of the particles' deposition sites depends strongly on
their aerodynamic diameters. In normal humans, inhaled nonhygroscopic part-
icles that deposit in the head and ciliated airways of the lungs by impact ion
are concentrated on a small fraction of the surface. Cigarette smoking and
bronchitis produce an increase in bronchial airway deposition. For non-
hygroscopic aerosols with aerodynamic diameters between 10 ym and 1 ym, an
increasing fraction remains airborne as particle size decreases, and is
exhaled. Total respiratory tract deposition in normals reaches a minimum of
about 10-20 percent for particles between 0.2 and 1 ym and increases for
particles, smaller than 0.2 ym. The major factor determining the probability
304
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of deposition of the smaller particles is their transfer from tidal to reserve
air, and they may remain airborne within the reserve and residual air for a
number of breaths before actually depositing.
The dominant deposition mechanisms are impaction (for particles larger
than 1.5 ym) , sedimentation (about 0.5 to 1.5 ym) and diffusion (smaller than
0.5 ym) . Deposition by sedimentation and diffusion produce relatively uniform
surface deposits in small bronchioles, alveolar ducts, and alveolar sacs.
Hygroscopic particles grow rapidly within the warm, moist airways, becoming
dilute aqueous droplets that can be three to five times the diameter of the
inhaled particles.
For particles soluble in respiratory tract fluid, systematic uptake may
be relatively complete for all deposition patterns, and there may be local
toxic and/or irritant effects. On the other hand, slowly soluble particles
depositing in the head beyond the anterior nares or on ciliated tracheobronchial
airways will be transported by the surface flow of respiratory-tract fluid to
the glottis and will be swallowed within one day or less.
Mucociliary transport rates are highly variable, both along the ciliated
airways of a given individual and between individuals, depending on the thick-
ness and character of the secretions and the number and beat rate of the cilia.
Effective fluid movement depends on the coupling of the ciliary motion within
the sol layer with the more viscous overlying layer. A moderate increase in
secretions, such as those produced by a few cigarettes or therapeutic dosages
of some adrenergic drugs, can result in acceleration of mucus transport.
Larger dosages or long-term exposures, which can cause an increase in the
number and/or size of the secretory cells and glands, can produce mucus layers
too thick to be propelled effectively by the cilia, and clearance stasis and
periodic retrograde flow can result.
Mucociliary transport rates decrease distally within the bronchial tree.
The total duration of bronchial clearance in normal humans varies from about
2.5 to 20 hours. The changes in clearance rates produced by drugs, cigarette
smoke, and various occupational dust exposures, can increase or decrease
these rates by large factors, sometimes by an order of magnitude. However, the
importance of alterations of mucociliary transport in the pathogenesis of
chronic lung disease is not yet clear.
Particles deposited in nonciliated airways have large surface-to-volume
ratios, and therefore, significant clearance by dissolution can occur for
materials generally considered insoluble. They can also be cleared as free
particles, either by passive transport along surface liquids or, after phago-
cytosis, by transport within alveolar macrophages. If the particles penetrate
the epithelium, either bare or within macrophages, they can be sequestered with-
in cells or enter the lymphatic circulation and be transported to pleural,
hilar, and more distant lymph nodes. In most cases, the quantitative aspects
of these clearance pathways vary with the composition of the particles and are
poorly understood. Nontoxic, insoluble particles are cleared from the alveolar
region in a series of temporal phases. The earliest, lasting several weeks,
appears to involve the clearance of phagocytosized particles via a bronchial
tree. The terminal phases appear to be related to solubility at interstitial
305
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sites. The effects of Infectious diseases, cigarette smoking, and other
environmental factors on the kinetics of alveolar clearance are not known
adequately.
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63. Thomas, R. G. , An interspecies model for retention of inhaled particles.
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66. Morrow, P. E., Gibb, F. R., Davies, H., and Fisher, M. , Dust removal
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68. Casarett, L. J., The vital sacs: Alvelar clearance mechanisms in
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69. Jammet, H., J. Lafuma, J. C. Nenot, M. Chameaud, M. Perreau, M. LeBouffant,
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FATE OF INGESTED PARTICULATES
by
Dr. James Millette and Mr. M. Rosenthal*
Exposure Evaluation Branch, Epidemiology Division
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
ABSTRACT
People consume many solid particles everyday through food, water, and beverages.
A review of the literature shows that while there is no mass penetration of
particles through the walls of the gastrointestinal tract, there is consider-
able evidence that mineral fibers and other durable particulates do transmigrate
from the G.I. tract to other parts of the body. Several mechanisms for parti-
culate penetration have been, postulated and the mechanism may well be different
for different types of materials and for different sizes of particles. Pene-
tration of asbestos fibers is a relatively rare occurrence and is estimated
to be on the order of 1 fiber in 10,000. Once in the body, some fibers and
other particulates may be accumulated in certain tissues but many are cleared
and eliminated through the urinary tract.
Particulates form a general category which is not very well defined. In
the drinking water industry we loosely classify the particulate component as
pieces of material of varying composition ranging up to 100 micrometers in
size. The finding of particles larger than 100 micrometers (0.1 millimeter)
in publicly supplied drinking water usually brings vigorous complaints from
the consumer. The question of the lower limit of the size of particulates
has largely been ignored. In the present analytical techniques available for
water, particles smaller than 0.1 micrometer are not considered. The question
of what constitutes a particulate in food is far more difficult than when
considering water. Analyzing food for particulates is an extremely difficult
task.
If particulates swallowed with food, beverages, and water do not migrate
across the gastrointestinal mucosa of the alimentary canal, the question of
whether any Ingested particle could be a cancer risk would be greatly simpli-
fied. It is clear that the food and liquids one consumes everyday contain a
high number of solid particles and by far the bulk of the nondigested material
moves through the digestive system as illustrated in Figure 1 and is discharged
*Presented by Dr. James Millette. 313
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I MOUTHI
[PHARYNX (6 INCHES)!
IESOPHAGUS (9 INCHES)!
STOMACH
[DUODENUM (1 FOOT)!
[JEJUNUM]
IILEUMI
[LARGE INTESTINE (5 FEET)j
RNUSI
SMALL INTESTINE (20 FEET
Figure 1. Pathway of ingested .material not assimilated
by the gastrointestinal tract.
314
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in the feces. While enroute on a normal trip, which may take a number of
hours, some particles are coated with secretions, subjected to gastric juices,
digestive enzymes, and drastic pH changes from pH2 to pH8. Only particles
with certain sustaining traits can be considered candidates for direct trans-
port through the GI wall. A more complete discussion of the activities of the
digestive tract can be found in the appendix of this article.
Since asbestos and other durable fibrous materials placed directly in
the peritoneum of animals have resulted in malignant neoplasms, the questions
of which materials and how much can pass through the walls of gastrointestinal
tract are particularly important.
The results of three laboratories' investigations on asbestos fiber pene-
tration were described in one publication in 1974.1 The paper reported no
evidence of penetration of the G.I. mucosa by mineral fibers. Although a
review of the studies shows "their results to be suggestive, the studies them-
selves were not adequately designed to answer the full question of penetration.
In the first laboratory, three studies were performed. The first investigation
consisted of ten rats fed laboratory chow containing 5 percent ball--milled
chrysotile for 21 months. After nine years storage in formaldehyde, tissue
of the G.I. tract was prepared for electron microscopy. The digests of the
tissues of the G.I. tract contained chrysotile fibers but it was impossible to
tell whether the fibers had been in the mucosa or were a result of contamina-
tion. Unfortunately at the time the tissues had been preserved, tissue from
the G.I. tract was not isolated from other tissues and no attempt was made to
keep the formaldehyde solution that had been contaminated with asbestos con-
taining fecal material from contaminating the other tissues with asbestos
fibers. Fibers were found in the digests of the mesenteric tissue from both
test and control animals but because the experimental procedure used unfiltered
water and contaminated reagents, the findings could not be interpreted. No
fibers were found in sections of intestines examined with electron microscopy
but the amount of tissue searched was not given in the experimental details.
In a second study, still in the first laboratory, 20 unanaesthetized rats
were given 400 mg of amosite or taconite mine tailings in 1 ml of suspension
by gavage. Fibers were found in the digest of G.I. tract tissues in some but
not all of the rats given amosite. No data were given as to the amount of
tissue analyzed.
A third study incorporated finely ground amosite or taconite tailings
into oleomargarine to obtain 10 percent amosite content or 20 percent taconite
content. Fibers were found in the mesentery, lung, or kidney digests of some
of the animals exposed to amosite or taconite but not in the digests of the
control rat tissues. No data were given as to the actual amount of tissue
examined so it is impossible to estimate the significance of finding fibers.
In the second laboratory studies reported in the 1974 article, the gut
and other tissues of rats fed 0.2-0.4 percent crocidolite asbestos in butter
for varying periods of time were examined only with optical microscopy. No
evidence of fiber penetration was found. No data on the magnification used
or amount of tissue surveyed were given.
315
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Only partial data from the third laboratory was available for inclusion
into the report. Chrysotile and crocidolite "properly ground" were mixed
with butter to a 0.5 percent level by weight. Light microscopic examination
of tissue sections showed no asbestos fibers that had penetrated. Electron
microscopic examination of sections of small intestine and mesenteric lymph
nodes also showed no signs of penetration. Again, no data were given as to
the actual amount of tissue examined.
Together the results of the three laboratories suggest that there is no
mass penetration of fibers through the gut wall, but because of the contamina-
tion of the first laboratory and lack of sensitivity in the second and third
laboratories, the results in this 1974 article are not confirming evidence
that durable fibers cannot transmigrate from the gastrointestinal tissues to
the body.
A number of other investigators have addressed the question of digestive
tract penetration by particulates. A number of their findings support the
contention that particulate penetration is not a large scale event but does
occur.
One of the first reports on the subject showed electron micrographs of
asbestos fibers in many sites of the colonic epithelium and lamina propria
of rats fed a 6 percent asbestos diet for 3 months.2 Asbestos particles
found in the tissue were up to 1 micrometer in length. No data were given
on the size of the asbestos before feeding or the amount of tissue analyzed.
The authors postulated that the particles had migrated through the mucous of
the goblet cells into the cell itself and hence into the lamina propria.
In a human study, amphibole fibers were found in significant numbers in
the lung, liver, and jejunum in 29 of 39 Duluth, Minnesota residents with
oral exposure to mineral fibers in their drinking water lasting up to 15
years.8 Among 21 control residents of St. Paul, MN and Houston, TX only two
subjects were found to contain the amphibole type fiber, in each instance a
single fiber from a single tissue site.
The methods of penetration of the digestive tract are postulated to be
direct piercing of the cells by long fibers and pinocytosis of short fibers.
According to Volkheimer,^ particles in the nanometer size range can be
channeled through the intestinal absorptive cell (enterocyte) by a pinocytosis-
like process in minute bubbles with a diameter of up to 50 ran. Larger
particles, whose diameter is well within the micrometer range, are suggested
to be regularly incorporated by persorption. In this process particles are
"kneaded" into the mucosa during their passage through the digestive tract.
Volkheimer suggests that the particles pass between the epithelial cells into
the subepithelial layer. It is easy to conclude that when durable fibrous
materials are kneaded into the tissue some of the fibers would directly
pierce the cells. Asbestos is known to be taken in by cultured cells.
Gross et. al.,1 raised an important point in the question of penetration
of the digestive tract by solid particles. If penetration of the GI mucosa
by- particulates did occur, the amount of stored material in the intestinal
316
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submucosa and In mesenterlc lymph nodes would increase with age. Recent data
suggest that many of the particles which have penetrated may be cleared from
the body via the urinary tract. Amphibole fibers were found in the urine of
persons who had been drinking unfiltered water containing the mineral.
Asbestos fibers have also been found in the urine of a baboon forced to ingest
the material.11 In most individuals a balance between fibers taken in and
those cleared may be reached over time. Fiber concentration in tissue may in-
crease with age but at a slower rate than fiber penetration of the digestive
tract.
Nonasbestos materials also penetrate the digestive tract. In their mini-
review of intestinal absorption of particulate matter, Le Fevre and Joel list
a number of materials which have been reported to pass the intestinal barrier.12
These include colloidal metals, latex spheres, polyvinyl chloride pellets, and
iron filings. Volkheimer9 reports using starch granules, cellulose particles,
powdered rabbit hairs, charcoal, pollen and silicate crystals in his persorp-
tion studies. Cook reported finding nonfibrous particles of silica, diatom
fragments, fibers of iron, titanium and glass of probable man-made origin.
Attapulgite clay fibers have been reported in the urine of a person ingesting
large doses for medical purposes.*3
Little data were available on the rate of transfer of various solid
materials through the digestive tract. Estimates of the passage rate for
asbestiform fibers range from 1 fiber in 1,00010 to 1 fiber in 10,000.^
From the data provided by Cook and Olson10 for 4 subjects ingesting unfiltered
Lake Superior water over a number of years, the average concentration of fibers
in the urine was 0.66 x 106 per liter. Compared with the average fiber content
of Lake Superior water of about 100 million fibers per liter, this fact suggests
that as many as 1 in 200 fibers crosses the digestive tract. This estimate
assumes that a steady state between the number of ingested fibers and the number
of fibers eliminated in the urine could occur so that the number of fibers in
urine would represent the minimum number of fibers passing through the intestinal
mucosa. As indicated by Cook and Olson, even the ratio of 1 in 1000 fibers
passing seems remarkably large and may be modified by further measure.
The value of 1 fiber penetrating in 100,000 was determined using a rat
study in which an asbestos pellet weighing approximately 20 mg was introduced
into the stomach of rats by catheter. The value of 1 in 100,000 may be an
underestimate of what happens when fibers are ingested in water since the
number of individual fibers available for penetration was dependent on the rats'
ability to break up the pellet internally. The same researchers have reported
the passage of both chrysotile and crocidolite fibers across the gastrointes-
tinal wall and that the larger chrysotile fibers appear to pass at a higher
rate than short fibers.15
If there is a balance achieved between intake of fibers and excretion
through the urine, a maximum accumulated level of fibers in some tissues may
be attained. It is interesting to note that the highest accumulation of
chrysotile fibers in tissues (other than lung) reported by three independent
researchers were all on the order of 10 million fibers per gram of tissue.
See Table 1.
317
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TABLE 1. MAXIMUM TISSUE FIBER CONCENTRATIONS REPORTED FOR CHRYSOTILE
Fibers
Tissue per gram Chrysotile Exposure
Rat omentum1* 8.6 x 10s* 1% in diet for 6 weeks
Human liver8 10.9 x 10s** Unknown exposure over
lifetime
Baboon kidney cortex7 7.8 x 106* 3 x 1013 fibers/kg in
9 days
*Corrected for control tissue concentration.
**Corrected for blank filter concentration.
In another study, a single suspension of chrysotile asbestos was injected
into the stomachs of 10 anaesthetized rats.3 Asbestos fibers were found in
animals sacrificed 2 to 4 days later in the omentum (which surrounds the small
intestine), blood, spleen and brain. The authors postulated that long fibers
may pierce the gut like a needle, whereas pinocytosis may account for the
absorption of smaller fibers. Fibers in one tissue were as long as 15 ym and one
fiber in the blood was 23 urn long. Some questions have been raised about the
injection technique in that there might have been passage of fibers through
the needle tract into the abdominal cavity.
In a second experiment, the same researchers fed 10 rats a diet containing
1 percent chrysotile asbestos for 6 weeks.4 Tissues were prepared using a
procedure which included ashing, solubilization with dilute HC1, filtration,
ashing the filter and dropping a 5 ul aliquot of tissue suspension on an
electron microscope grid. Analysis of the tissues showed higher levels of
asbestos in all tissues of test animals examined than in controls with the
highest levels in the omentum (9.66 x 106 fibers per gram) followed by the
brain, lung, liver, blood and kidney. Fiber lengths were up to 5 um. The
authors concluded that ingested asbestos can penetrate the walls of the diges-
tive tract but that when the amount of asbestos consumed by the rats in the
6-week period is considered, the amount found in tissues represent an extremely
small portion.
One hour after amosite asbestos fibers suspended in saline were placed in
an isolated segment of rat jejunum in vivo, the animal was sacrificed and
fibers were found penetrating the epithelial surface.5 Amosite fibers with
diameters up to 1.4 um and visible lengths up to 30 um were seen in epithelial
cells or in the lamina propria. All fibers seemed to enter the cell through
its luminal surface. None penetrated the intercellular junctions. The authors
concluded that penetration of the epithelial cells of the intestine directly
through their cell bodies is at least one of the mechanisms by which asbestos
fibers can gain access to the lamina propria of the Intestine.
Fiber penetration of the digestive tract has also been documented in pri-
mates. * Chrysotile asbestos fibers up to 35 um long were found in the kidney
318
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cortex of a newborn baboon fed asbestos containing milk formula for 9 days.
Statistically significant higher levels of fibers were found in the kidney
(especially kidney cortex), lymph nodes, spleen, colon, and esophagus over
control tissues. Five other tissues, stomach, liver, duodenum, cecum, and
heart contained concentration of fibers not different from control tissues.
The tissue was prepared using a procedure of low temperature ashing, solubili-
zation with 1 percent acetic acid, filtration, ashing of the filter and placing
6 ul of tissue suspension on an electron microscope grid. There were fibers
of various sizes found in the test animal tissues indicating, at least with
the newborn, a range of sizes of asbestos fibers can penetrate.
This may indicate the upper level for chrysotile accumulation in tissue.
Other particulates may accumulate to different levels and be regulated by
different clearance mechanisms.
In summary, the research conducted on the penetration of the digestive
tract by solid materials is sufficient to conclude that such penetration is
not on a large scale but can and does occur. Research findings also suggest
that while some fibers may be entrained in body tissue many are cleared through
the urinary tract.
REFERENCES
1. Gross, P., R.A. Barley, L.M. Swlnburns, J.M.6. Davis, and W.B. Greene.
Ingested mineral fibers, do they penetrate tissue or cause cancer. Arch.
Envir. Health 29:341-347 (1974).
2. Westlake, G.E., H.J. Spjut, and M.N. Smith. Penetration of colonic mucosa
by asbestos particles. Lab. Invest. 14(11):2029-2033 (1965).
3. Pontefractj R.D. and H.M. Cunningham. Penetration of asbestos through
the digestive tract of rats. Nature 243:352-353 (1973).
4. Cunningham, H.M., C.A. Moodie, G.A. Lawrence, and R.D. Pontefract.
Chronic effects of ingested asbestos in rats. Arch. Envir. Contain.
Toxicol. 6:507-513 (1977).
5. Storeygard, A.R. and A.L. Brown. Penetration of the small intestinal
mucosa by asbestos fibers. Mayo Clin. Proc. 52:809-812 (1977).
6. Patel-Mandlik, K.J., W.H. Hallenbeck, and J.R. Millette. Asbestos fibers:
(1) a modified preparation of tissue samples for analysis by electron
microscopy, (2) presence of fibers in tissues of baboon fed chrysotile
asbestos. J. of Envir. Path. Toxic. 2:1385-1395 (1975).
7. Patel-Mandlik, K.J. and J.R. Millette. Evidence of migration of ingested
asbestos into various baboon organs. Scanning Electron Micr./-1980/l,
347-354 (1980).
8. Carter, R.E. and W.F. Taylor. Identification of a particular amphibole
asbestos fiber in tissues of persons exposed to a high oral intake of
the mineral. Envir. Res. 21:85-93 (1980).
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9. Volkheimer, G-., Passage of particles through the wall of the gastrointes-
tinal tract. Envir. Health Persp. 9:215-225 (1974).
10. Cook, P.M. and G.F. Olson. Ingested mineral fibers: elimination in
human urine. Sci. 204:195-198 (1979).
11. Hallenheck, W.H. and K.J. Patel-Mandlik. Presence of fibers in the urine
of a baboon gavaged with chrysotile asbestos. Environ. Res. 20(2):335-340
(1979).
12. LeFevre, M.E. and D.D. Joel. Minireview: intestinal absorption of parti-
culate mater. Life Sci. 21:1403-1408 (1977).
13. Bignon, J., P. Sebastien, A. Gaudichet, and M.C. Jaurand. Biological
effects of attapulgite. Symposium on Asbestos, Lyon, France (1979).
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"Translocation of asbestos fibers through respiratory tract and gastro-
intestinal tract according to fiber type and size." Dusts and Disease,
R. Lemen and J. Dement (eds), SOEH, Pathotox Pub., Park Forest South,
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15. Sebastien, P., R. Masse, and J. Bignon. Recovery of ingested asbestos
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(1980).
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APPENDIX
THE DIGESTIVE PROCESSES
Ingested material, whether it is considered food or foreign matter, must
eventually either pass through the alimentary canal (gastrointestinal tract)
or be assimilated by the body somewhat along the twenty seven or so feet of
the canal.
Ingested material enters the 61 tract through the mouth (and sometimes
through the nasal cavity due to swallowing of material cleared from the res-
piratory tract). In the mouth, ingested material is acted upon by secretions
from the Parotid, Submaxillary and Sublingual Salivary Glands. These secre-
tions serve primarily to moisten the ingested material and mouth tissues, and
to initiate the breakdown of ingested starches. Mastication serves to break
up the material mechanically.
The ingested material then passes through the pharynx and into the
esophagus, a short mucous-lined tube capable of producing wave like peristaltic
motion that aids in moving material to the stomach. In the stomach lining,
there are a number of specialized glandular cells whose function is to secrete
digestive enzymes, buffers, hormones and hydrochloric acid. Ovoid parietal
cells, in the lining, are stimulated by the vagus nerve, gastrin and histamine
to secrete HC1 into the lumen of the stomach. Mucous and alkaline fluids,
secreted by the stomach lining, protect the stomach from being eaten away by
the acid, which may range anywhere from pH 0.9-3.0 depending on the nature of
the ingested material and the overall health of the individual. Some fluid
absorption occurs in the stomach.
As the ingested material proceeds along its course into the duodenum of
the small intestine, it is acted upon by alkaline pancreatic juices, NaHCOs,
insulin, glucagon, enzymes and proteins from the pancreas, bile from the liver
and gall bladder; and secretin, duodenal juice, succus entericus and pancre-
ozymin from the intestinal cells. The thick carpet of finger-like projections
(villi) that line the small intestine allow for greater surface area and there-
fore more absorption. Most of the liquids, amino acids, sugars and other
nutrients are taken up into the bloodstream via capillary beds among the villi
and the hepatic portal vein (leading to the liver). This transport can occur
by means of absorption, persorption or pinocytosJ.s.
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The non-assimilated portion of the'ingested material proceeds to the large
intestine where water, salt and glucose are absorbed from the fecal material.
The fecal material then passes through the rectum and out the anus.
In man, the time period for the complete passage of non-assimilated
ingested material will vary with each member, but usually ranges between
20 and 25 hours.
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DISCUSSION ON THE ROUTES OF EXPOSURE: INHALATION,
DEPOSITION AND CLEARANCE OF PARTICLES
REMARK (Dr. Gross): I am associated with the Industrial Health Foundation.
I wish to comment on some of the statements that have just been made.
I have been a pathologist over the last 50 years. Half of that time
was in hospitals where I spent a good deal of time studying the tis-
sues of hospital patients who died as a result of their illness.
One of the organs that was studied in great detail was the kidney.
I have always been Impressed from a clinical point of view upon the
exquisite ability of the circling unit of the kidney to hold back dis-
solved molecules of proteins that have a fairly high molecular weight
and allow molecules of low molecular weight such as electrolytes
to pass through.
When one considers the comparative size of a particulate, particu-
larly a fiber, in relation to a micro-molecule such as albumin, which
under normal conditions the circling membrane of the glomerulus (a
unit in the kidney) holds back, there is an enormous difference and
according to what Dr. Millette just said, quoting Dr. Cook's
work, the passage of participates through the renal circling membrane
is not an unusual event. This is totally out of keeping with what we
know of kidney function, the ability of the membrane of the glomerulus
to hold back even dissolved molecules of appreciable size.
With regard to the passage of particles through the intestinal mucosa
Dr. Millette quoted Volkhelmer, who in his article claimed to find
starch granules in the blood, in various tissues, and in the urine.
These starch granules are 10 times the size of a red corpuscle and in
order to pass, say through the intestinal wall into a blood vessel
of any size it ultimately will have to pass through the capillary
network that barely allows a single red corpuscle to pass through.
Yet, we are supposed to believe that Volkhelmer was able to demon-
strate such huge particles in the urine.
As an example of the ability of the intestinal mucous membrane to
hold back particles that happen to be in the intestinal ileum, I
might mention that coal miners swallow a good deal of the dust that
they inhale and in the swallowed coal dust are particles that are a
fraction of a micron in diameter. If fibers, which are 1 micron
in diameter, are capable of passing through the intestinal wall,
then particles that are a small fraction of that size would have even
a greater facility to pass through. Now, a coal miner may work in a
coal mine for 30 years and every day he would swallow a fairly large
amount of coal dust that he has inhaled and was brought up from his
lungs, yet when one does autopsies, as I have done, on coal miners
one does not see black discoloration of the lymph nodes. One rarely
sees black spots in the liver and spleen, but that can be explained
on the basis of lymphatic drainage from the lungs. But, one cannot
see black lymph nodes in the mesentery, the lymph glands that drain
the intestinal wall. One does not see that and one would see it if
particles were capable of penetrating the intestinal wall.
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You realize, of course, that I look with a very jaundiced eye on this
presentation and I hope the audience will also be judicial in accept-
ing this presentation.
REMARK (Dr. Kotin): I work for Johns-Manville Corporation. A couple of
comments on the papers and then perhaps a few generalizations.
First, let me thank you, Dr. Rowe, for being sensitive enough to
dedicate this session to Mearl Stanton. As a former associate of
his at NCI there is no way we can overstate our debt to him and his
associates. Also thanks for being good enough to stop me in the cor-
ridor to say I can talk for a few minutes if I want.
I am not sure that the case for penetration of the gut has been made
by this presentation, but penetration of the gut does occur and I
think that the criteria for penetration are probably not for this
session.
I think that Dr. Millette might be well advised to know that both
Doctors Cunningham and Pontefract were aware belatedly that the
formaldehyde that they used for the fixation of tissues was loaded
with asbestos fibers. Unfortunately it was filtered through asbestos
and I think they are very candid in stating this, but in no way
would I say that that necessarily throws out all of their data. I
think quantitatively it might be challengable.
Again, I think the best thing that can be said about the Storeygard
and Brown study is what Dr. Brown says himself. They were dealing
with an exteriorized loop of intestine. He cannot be sure that he has
got penetration or overlay on many of the sections, which I reviewed
with him personally, so let us at least maintain the fact that maybe
not these studies but others may very well substantiate the concept
of penetration.
Dr. Lippmann, I think you might know that, and I am sure you are
aware that Crystal and his associates at the Heart and Lung Insti-
tute are beginning to show, I think rather reliably and consistently,
a role for the poly as well as for the macrophage in the fibrogenic
capabilities. I think this has some relevance to the pathogenesis
of a disease in people who are exposed to excessive amounts of
asbestos.
Again, I have no new data to present because of the brevity of time,
but let me restate a few verities that probably have been lost
sight of and certainly I think have been given short shrift in the
presentations.
Let me begin immediately by saying that the reality of asbestos-
related disease has been amplified by the presentations at this meet-
ing. I think at the very least you would have to have your sanity
questioned to doubt the capability of excessive amounts of asbestos
fibers to produce an array of asbestos related conditions. However,
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the disease-producing potential can not be divorced from accepted princi-
ples of pharmacology, toxicology, pathogenesis, pathology and clinical
disease. Specifically, these principles include factors like dose
response; multifactorial etiology in both disease development and
disease natural history; the demonstration by several, including a
person attending this conference, of a no adverse- effect level in a
very competently studied population; and the necessity for biological
availability for host effect, which, of course, relates to the two
earlier presentations. This includes things that have been discussed
before; localization, retention, translocation, the dimension of the
particles, the solubility of the particles, and I think all these
principles, and one could go on listing many more, find expression
and are all applicable to the problem of asbestos exposure and one
that is particularly relevant to EPA. I do not envy EPA's responsi-
bility in trying to address the issue of asbestos outside the work
place. OSHA has by far the easier of it.
The patterns of asbestos-related disease in occupational settings
are well known. The patterns of asbestos response in para-occupational
settings, neighborhood studies, and family studies have not been
shown and this does not mean that the positive studies are useless.
Not at all. What they do clearly demonstrate is that even outside the
workplace dose response has its universal application.
Perhaps a fourth pattern of exposure to asbestos-related disease,
and this does put the EPA right in the middle of the circle, is a
category, for want of a better term, I call "living with asbestos."
This includes the school buildings. This includes asbestos as part
of the earth's crust where it is indeed part of the potable water
supply or part of the airborne suspended material as a result of
wind and soil erosion. For this group, really, and I can only
repeat what Dr. Rowe said, the data are pitifully little and really
do not permit conclusions nearly as much as they permit what Sir
McFarland Burnett called in his Nobel speech, "responsible specula-
tion." The data do permit responsible speculation that the "living
with" group does not have any asbestos-related disease as yet. One
gives added credence to the negative data because you do have two
marker situations, mesothelioma and a rather characteristic type of
fibrosis. But this is not to say that the answer is in by a long
shot.
Then you have the fourth category and this is the casual exposure and
I mean casual not in the cultural sense. I mean casual in a quantita-
tive sense; not the people in this room; you either work with asbestos
or are using it in your laboratory or so on, but the next crowd that
goes to see the Redskins play would predominantly be people casually
exposed. Here, again, I think despite ongoing studies that have been
comprehensive, yet inadequate, there is absolutely no evidence of an
effect.
I would make two major closing comments. First, the assumption that
all four classes are interchangeable in terms of the generalizations
I have made is not true of course. The dosage of exposure is different,
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the co-factors differ and so on. So, I think one has to be very,
very jealous in terms of the discipline in which one approaches each
of these categories and tries to conclude from one to the other.
The second point I would like to make is that the four categories,
again, in no way contradict the occupational information that we have
about asbestos but, again, I would emphasize the importance of dose.
The assumption that doses, particularly in the para-occupational
exposures, are low dose exposures, I do not think is a valid one on
the basis of existing data, but the data are so pitifully small that
one cannot either deny or assent; one can only say that much more
information is necessary. Again, a short exposure is not necessarily
a low dose exposure and a nonoccupational exposure may not be, either.
Let me close by saying one word on substitutes. Clearly the princi-
ples of biology that are applied to asbestos have to be applied to
all substitutes, as 1 know in fact they are being applied, but it
would be well to not repeat some of the omissions in our approach
to the asbestos problem that have been taking place over the last
half century in addressing these substitutes.
QUESTION (Mr. Kosner): I am from the NIEHS. We certainly owe a great debt
to Dr. Kotin who is also the founding director of the National
Institute of Environmental Health Sciences, the institute that I am
with at the present time.
We do know that asbestos is associated with mesothelioma of the pleura
and of the peritoneum. Unless we believe these substances act at a
distance, we would have to believe that the particles must get to
these sites in order to set up the conditions for the effect to occur.
I wonder if something also could be said about the stability of dif-
ferent types of fibers. For example, asbestos is quite different than
fiberglass and some others in terms of its resilience and in terms of
its strength and some other factors. It may be that some of these
stay pretty much as they are, whereas other* ones tend to break up and
might be eliminated more rapidly. The way more sense is going to be
made from this field in which so many different substances are being
used is to find out these basic principles of uptake and release and
integrity. We do know something about the Importance of the length
to the diameter.
Does Dr. Millette know something about the integrity of different
types of fibers; rock wool versus fiberglass versus asbestos, et
cetera?
ANSWER (Dr. Millette): In terms of ingestion there certainly is very little
data on any material other than asbestos that has even been attempted.
So, all you would have would be the casual findings of certain other
types of fibers in other tissues, such as, gastrointestinal tissues,
or finding, say, attapulgite fibers in the urine of a person receiv-
ing it in a high medical dose. So, very little really has been done
with that.
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REMARK (Dr. Rowe): That was a very good comment and question. I think
that is an area that will have to be avidly pursued in the
future.
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MAN-MADE VITREOUS FIBERS AND HEALTH
by
Jon L. Konzen, M.D.
Medical Director, Owens-Corning Fiberglas Corporation
Chairman, Medical & Scientific Committee of TIMA
Mount Kisco, New Tork
ABSTRACT
Asbestos fibers and manmade vitreous fibers differ in durability, fate and
ability to cause disease. In man, asbestos is known to cause botb malignant
and non-malignant disease. In man, there is no credible evidence of malignant
or chronic progressive non-malignant disease resulting from exposure to
man-made vitreous fibers.
Airborne exposures of man-made vitreous fibers observed during manufacture,
fabrication and installation are extremely low. With .few exceptions, they
are well below 1 fiber per milliliter.
No chronic progressive disease, either malignant or non-malignant, has been demon-
strated to date by Inhalation of man-made vitreous fibers in animal studies.
Animal models demonstrate disease only as a result of non-physiologic exposure
to long thin fiber by surgical implantation (mesothelioma) and by intratracheal
injection (fibrosis).
GENERAL
Man-made vitreous fibers which include fibrous glass, rock and slag wool
and ceramic fibers are products of 20th century technology. Mineral and slag
wool were first manufactured in the early years of this century while fibrous
glass was first produced in the 1930*s and ceramic fiber roughly a decade
later. These materials are used for thermal and accoustical insulation and
reinforcement applications. Presently only a few of these applications overlap
with asbestos usage and, therefore, man-made vitreous fiber cannot he considered
truly a substitute for asbestos.
DIFFERENCES - ASBESTOS VS MAN-MADE VITREOUS FIBER
Vitreous fibers have come under suspicion as possible malignant or non-
malignant disease producing materials largely because they are fibers. The
dimensions of the smaller vitreous fibers overlap the dimensions of the larger
asbestos fibers. The similarity ends there. It is useful to contrast man-made
vitreous fibers and asbestos in terms of durability and fate.
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Durability
Fibers vary significantly in their durability or survival in living tissues.
Gypsum disappears within hours after implantation, whereas some types of asbestos
fibers can survive within tissues for the full life-span of exposed animals and
humans. Between these two extremes there are varying intervals of durability
for fibers of many types. Experimental studies1 (e.g., Kuschner and Wright)
report data suggesting that very fine man-made vitreous fibers have a marked
tendency to disappear when compared to asbestos fiber.
Both in vitro and in vivo studies have shown that man-made vitreous fibers
have a greater solubility than many asbestos fibers. (This should not be sur-
prising when one considers the recognized variations in solubility among the
several types of asbestos). Kuschner and Wright reported a fibrogenic response
to very thin glass fibers (less than one micron in diameter), but, paradoxically,
no biological effect of ultrathin fibers (less than 0.3 microns in diameter).
After special efforts were made to ensure that this finding was not an artifact,
the researchers were reasonably convinced that it was related with the dis-
appearance of fibers.
Fiber Fate
Experimental studies in animal models and in humans have demonstrated that
fibers can undergo cleavage, splitting, or fragmentation in the lungs.1'2 This
property varies among fibers, and, in fibrogenesis and cancer induction, it is
of critical importance. Asbestos fibers are multifilamentous and split longi-
tudinally, or along the long axis, into progressively thinner components that
have been shown to be associated with chronic, progressive non-malignant and
malignant disease in humans. Asbestos fibers fragment transversely with much
less ease and frequency. In sharp contrast, man-made vitreous fibers are mono-
filamentous and do not split longitudinally into fibrils. Rather, they split
and fragment only along.the transverse axis, thereby becoming progressively
shorter.3 When one looks at the hilar lymph nodes draining the lungs of
experimental animals, one can find fragments of vitreous fiber shorter than
that to which the animals were exposed; thus some of the fibers may have been
broken up in the lungs. With the long thin fiber concept, in which short
fibers are recognized as being non-pathogenic, this property of man-made
vitreous fibers moves them in the direction of less and less pathogenicity.
MAN-MADE VITREOUS FIBER PRODUCTS
Man-made vitreous fibers are produced in two broad categories: wools and
textiles. Man-made vitreous fiber wool is used for example in commercial,
industrial and residential insulation; acoustical ceiling panels; air-conditioning
ducts; and mat products. The textile fibers or glass fiber yarns, roving and
chopped strand mats have numerous applications including decorative and indus-
trial fabrics; reinforcements for plastics, rubber and paper; electric insul-
ation; filtration; and roofing materials.
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FIBER DIMENSIONS AND RANGES
Man-made vitreous fiber manufacturing processes, especially the wool pro-
cesses, do not produce fibers with absolutely uniform diameters. The diameters
of the fibers in each product vary, hence the diameter of the majority of fibers
in the product determines the "nominal diameter". If the actual diameters of
man-made vitreous fibers produced by a particular process are plotted on a graph,
the overwhelming majority of them will be "near" the nominal diameter. Gen-
erally, the further from the nominal fiber diameter one gets, the fewer fibers
one will find - giving what often looks like a bell-shaped curve when the fiber
diameters are plotted.
Although the vast majority of all man-made vitreous fibers products have
a nominal diameter of 6 microns or greater, all products contain some fibers
with diameters equal to or less than 1.5 microns. For over fifty years workers
have been exposed to some fibers equal to or less than 1.5 microns in diameter
contained in all products. Epidemiological studies of this worker population
have failed to identify credible evidence of chronic, progressive non-malignant
or malignant disease associated with this exposure.
Wool Fiber
Wool fibers are amorphous silicates made by blowing or spinning (fiberizing)
a stream of molten vitreous material into fibers. Rock or slag wool fibers
traditionally are made from furnace slag and/or limestone. In recent years,
raw materials such as basalt, iron slag and phosphate slag have been used. Fib-
rous glass wool fibers are made from glass compositions that are carefully con-
trolled formulations of silicon* aluminum, boron, calcium, sodium and other
metal oxides.
Most products manufactured from the wool processes contain fibers that
range in nominal diameter from approximately 6 to 9 microns. However, such
products manufactured for over 50 years always have contained a small percen-
tage of fibers with diameters equal to or less than 1.5 microns with lengths
varying from 5 to 60 microns.
Textile Fibers
Textile fibrous glass products generally have larger nominal diameters
than man-made vitreous wool fiber products. These textile fibers are drawn
or extruded from holes in the base of the fiberizing equipment in a process
which produces continuous fibers of infinite length, nominal diameters ranging
from 6 to 25 microns and a very narrow range of diameter distribution. The
majority of textile fibrous glass is used in reinforcement applications where
a larger fiber diameter is desired for its superior reinforcing properties.
For this reason, most of the textile fibrous glass produced are the larger
diameter fibers. The finest diameter textile fiber, which has a nominal dia-
meter of approximately 4 microns, is produced in relatively small quantities
and is used for specialized fabric applications. Because of the controlled
manufacturing process, textile fibrous glass contains only a minute amount of
fiber with diameters less than or equal to 1.5 microns.
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Fine Diameter Fibers
Fine diameter fibrous glass, which is produced by a flame-attenuated pro-
cess, may include fibers that have a nominal diameter as low as 1 micron.
These fibers have been produced on a commercial basis since the early 1940's
in limited quantities.*
Very Fine Diameter Fibers
Very fine diameter fibrous glass, with a nominal diameter of less than 1
micron, is manufactured for certain highly specialized applications, such as
aerospace insulation and sophisticated filtration and represents less than
1 percent of all production.
Ceramic Fibers
Ceramic fibers are wool-like products made from molten aluminum silicate.
They have a nominal diameter of approximately 2 to 4 microns and a range of
actual diameters from 0.5 to 12 microns, skewed towards the larger diameter
fibers. These fibers are primarily used for high temperature applications in-
cluding thermal blankets for industrial furnaces and vacuum cast parts for
speciality products used in high temperatures.
BIOLOGICAL EFFECTS OF MAN-MADE VITREOUS FIBERS
Investigations into the health effects of man-made vitreous fibers can
best be discussed under the headings of sampling studies, animal studies, in
vitro studies and human studies. These fibers which have been in commercial
use, for over 50 years, have failed to demonstrate any chronic, malignant or
non-malignant pulmonary disease in man. In laboratory animals disease has
been produced only when fibers were administered by an artificial route which
bypassed physiologic defenses. The airborne concentrations of man-made
vitreous fibers have consistently been demonstrated to be remarkably low,
both in areas of manufacture as well as in areas of handling, application
(with the exception of blowing applications) and use. Each of these points
will be reviewed briefly, touching only on the most important aspects. No
attempt will be made to cover every article which has been written on the
subject.
I. Industrial Hygiene Studies
Several industrial hygiene studies have been reported.5 The results of
these studies are remarkably consistent. In general the airborne fiber con-
centration in ordinary wool fibrous glass manufacturing operations is 0.1
fiber or less per milliliter for airborne fibers less than 3.5 microns in
diameter with about 25 percent of this material less than 1 micron in diameter.
It is unusual to find airborne concentrations approaching 1 fiber per milli-
liter. While the lengths were variable, the majority of the fibers noted were
longer than 10 microns. In the finer diameter fiber products (average diameter
of 1 micron or less) the airborne concentration may exceed 1 fiber per milli-
lite*r in manufacturing and fabrication areas. Esmen6 demonstrated that,
generally, speaking, as the nominal diameter of the products increased the
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airborne concentration decreased. Similar findings were demonstrated in fabri-
cation* packing and cutting areas of the plants. Industrial hygiene findings
have shown that ftfr any wool product, the average diameter or airborne fiber
resulting from manufacture or fabrication operations will be smaller than the
average diameter of, the product. As an example, the average diameter of build-
ing insulation runs from approximately 6 to 9 microns while the average dia-
meter of airborne fiber resulting from the manufacture or fabrication of this
material will be in a range of approximately 1 of 2 microns. It can be gen-
erally stated that the light microscopic counts will be approximately equal
to the electron microscopic counts for ordinary type fibrous glass. This
does not hold true for the special finer fiber products (average product dia-
meter of 1 micron or less) where the electron microscopic count may be greater
than the count by light microscopy.
Esmen,7 in a recent study for the Thermal Insulation Manufacturers Asso-
ciation to determine airborne fiber concentrations in operations utilizing
man-made vitreous fibers, has demonstrated that during a field installation
of thermal insulation materials including ordinary building insulation,
acoustical ceiling and fibrous glass duct insulation, the average airborne
concentration of fibers was well below 1 fiber per ml with the exception that
during the application of blowing wool into closed attic spaces the time-weighted
average airborne concentration ranged up to 6 fibers per ml.
In this same study, Esmen reported industrial hygiene sampling of aircraft
insulation fabrication where the material was being sewed, cut and cemented.
This material is high efficiency, specialized insulation which is 1 micron in
nominal diameter. The airborne concentration was generally below 1 fiber per ml.
II. Animal Studies Involving Man-Made VjLtreous "Fibers
Although animal studies have been undertaken since the 1930's, the most
pertinent studies include Gross'8 inhalation study in 1970 where he exposed
rats and hamsters to 100 mg per cubic meter of air of fibrous glass that had
a nominal diameter of approximately 1 micron and a diameter in the chamber
air of 0.5 microns. Seventy percent of the airborne material was reported to
be fibrous. The fiber lengths were between 5 and 20 microns. These studies
demonstrated no appreciable alteration of lung architecture, minimal pleural
change, no significant fibrosis and no tumor development in animals exposed
for 24 months and domiciled for the remainder of their lifetime. Other inhala-
tion studies by Botham and Holt,9 Timbrell,10 Harris,11 Harris and Fraser,12
Lippmann13 and Brain1** utilizing fibrous glass, designed to look at such things as
deposition and clearance as well as pathological changes, demonstrated
non-specific pulmonary responses with a relatively wide variation but no tumor
formation or significant fibrosis.
Wagner,15 in England, has recently reported that his inhalation experi-
ments utilizing a very fine diameter fibrous glass with a mean diameter of 0.3
microns and rock wool with a mean diameter of 0.8 microns, have failed to
demonstrate fibrosis with the only reaction being a minimal non-specific cellu-
lar dust response. This study is still on-going and must await completion for
final evaluation.
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A number of Intratracheal injection studies have been carried out over
the years beginning in the late 1930's. The more significant studies were
those carried out by Gross,8 and by Wright and Kuschner.1 These studies
demonstrated a wide variety of cellular response with no significant chronic
pulmonary effects, with the exception of the Wright-Kuschner study. Wright
and Kuschner demonstrated a peribronchiolar fibrosis in guinea pigs intra-
tracheally injected with long thin fibrous glass. This response was qualita-
tively similar to a response to chrysotile asbestos but quantitatively much
less. The authors commented that this information could not be directly
extrapolated to man because the method or administration bypassed all natural
respiratory defense mechanisms. The study did show, however, that massive
doses artificially placed at the target site caused fibrosis if the fibers
were significantly long and thin (less than 1.5 microns in diameter and
greater than 10 microns in length). The authors felt that additional inhala-
tion studies using long, thin fibers were indicated. Such studies are now
being conducted.
Quite significantly, malignant tumors have not been produced by intra-
tracheal injection of man-made vitreous fibers with dimensions known to
produce them by surgical implantation. The Wright-Kuschner intratracheally
injected animals were sacrificed after 2 years and Gross8 animals, similarly
exposed, were permitted to live out their lives.
Intracavitary implantation in animals of man-made vitreous fibers as
well as a variety of other fibrous materials has been carried out by a number
of investigators16'17'18'19'20 in this country and abroad. Mesotheliomas have
been produced at the sites of surgical implantation and injection into the
pleural and peritoneal cavities of animals using high doses of many types of
materials. The materials included specially prepared long, thin fibrous glass
fibers (fibers less than 1.5 microns in diameter and greater than 8 to 10
microns long). The implantation of the type of fibrous glass commonly used
as insulation material however, which does contain some fibers less than 1.5
microns in diameter, failed to elicit mesothelioma production.21 Stanton,16
who performed the major surgical implantation study, noted that "Direct appli-
cation of our results (the implantation study findings) to the problems in man
would be unwise because of the method of application and the high doses used
are remote from the usual exposure of man to fibers ..."
III. In Vitro Effects
A number of studies have been conducted in vitro. The reported results
have been mixed.22'23 The question arises for the need to test man-made
vitreous fibers in an in vitro system since it has been demonstrated in vivo
that long thin fibers, when implanted into the abdominal and chest cavities,
do cause mesotheliomas. It is suggested that the human health effects of
man-made vitreous fibers are best evaluated through further animal studies and
by epidemiology. Such studies are currently underway. The progress of one
of these studies is being reported here at this symposium.
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IV. Cross Sectional Studies of Currently Exposed Workers
Cross sectional studies have been carried out since 1942 on man-made
vitreous fiber exposed workers. These studies have been largely fibrous glass
exposed workers. Several of these studies have been carried out at the same
plant. That facility is the oldest continuously producing fibrous glass plant
in the United States. This plant has been repeatedly studied by Wright, by
deTreville, by Nasr and by Utidjian utilizing cross sectional morbidity techni-
ques. Wright studied 1389 fibrous glass workers who were employed from 10
to 25 years. The study demonstrated no unusual pattern on chest roentgenograms
that could be attributed to fibrous glass exposure. Utidjian25 reported the
evaluation of 232 randomly selected workers from this same plant. The study
demonstrated no major effect on lung function after long term exposure.
deTreville,26 using a subsample of Utidjian's workers, which included 30 long
term fibrous glass workers, 15 with minimal and 15 with heavy subjective
exposure, evaluated the subjects for cardiac and pulmonary status including
blood gas studies. He noted no significant differences between the two groups
of exposed workers. Nasr,27 examining 2028 chest x-rays of fibrous glass
workers in this plant, observed no difference in the Incidence of abnormalities
between the exposed factory workers and non-exposed office workers and no
radiographic effects resulting from fibrous glass exposure. Hill,28 in evalu-
ating 70 workers with occupational exposure to fibrous glass with an average
exposure time of approximately 20 years, found that chest x-rays and pulmonary
function studies of the workers were not significantly different from an un-
exposed group matched for age, height and weight.
Gross,29 comparing the lungs of 20 insulation fibrous glass manufacturing
workers whose periods of exposure ranged from 16 to 32 years to the lungs of
26 urban dwellers with no history of fibrous glass exposure in the workplace,
noted no significant difference in lung fiber content or fiber dimensions
between the groups. He further concluded that long term exposure to the dust
of fibrous glass caused no gross or microscopic pulmonary damage.
Upper respiratory irritation has been reported by several authors.30*31'32'
33'3lf It is often found following unusually dusty conditions, particularly in
situations involving the dry method of tearing-out of installed man-made vitreous
fiber materials. After the initial irritation has passed there is complete
resolution of the condition.
Transitory skin irritation by man-made vitreous fibers in some workers
is known to occur. This has been reported by many authors35'36'37'38'39 over
the years. All authors agree that it is a mild, mechanical irritation which
lessens in intensity after several days of continuous occupational exposure.
The ability to cause irritation is related to the diameter of the fiber. The
larger the diameter of the fiber, the more likely the material is to cause
irritation. There is no evidence that the skin irritation is other than a
transitory mechanical one. There is no allergic component.
V. Mortality Studies Involving Man-Made Vitreous Fibers
The above mentioned cross sectional morbidity studies are useful in iden-
tifying a lack of non-malignant "dust related" disease. However, such studies
335
-------
could fail to demonstrate disease which had a long latent period. For this
reason, epidemiological mortality studies of workers with long exposure to
airborne fibrous glass in manufacturing operations have been done. Such studies
have been carried out and are currently in progress. Among these studies is
Bayliss l**°'t*1'1*2 work which included 1448 workers occupationally exposed to
fibrous glass. This study found no significant malignant respiratory disease,
20 or more years after onset of fibrous glass exposure. The author did note
19 non-malignant respiratory disease deaths, excluding pneumonia and influenza,
compared to an expected 10 deaths. However, more than half of the decedents
had previous exposure in dusty environments, including nine in a foundry, one
in a silica batching operation and one with an exposure in coal mining. Fur-
ther, smoking histories were not available. The plant population used in the
Bayliss study was the same as used on different occasions by Wright, Nasr,
Utidjian and deTreville. Therefore, it seems likely in light of the work his-
tories involved that any significant non-malignant respiratory disease would
have been discovered by these studies. The proposition that susceptibles
would select themselves out of the working population is not realistic. A
case in point is the all too common findings of asbestosis—a legacy of past
exposure—being identified in current asbestos exposed workers.
The Bayliss case control study, which attempted to study malignant and
non-malignant disease in manufacturing workers exposed to finer diameter fiber
(1 micron average diameter) was inadequately designed and analyzed, and
incorrectly classified some of the workers as having contact with finer fiber.
The results were reported as borderline statistically significant.
Recently Enterline^ reported his findings on the first eight plants in
a study that will encompass 17 man-made vitreous fiber manufacturing facilities.
This study has not considered smoking histories, which were unavailable. The
initial study group of eight plants included 7049 workers, 6023 workers from
five fibrous glass manufacturing plants and 1026 workers from three rock wool
or slag wool plants. Compared to expected deaths from all causes in the United
States, the initial report indicated 7 percent fewer deaths among the cohort.
Twelve percent fewer deaths than expected were attributed to respiratory can-
cer. Thirteen percent fewer deaths than expected were attributed to malignant
disease of the digestive organs or peritoneum. Five percent more deaths than
expected were attributed to non-malignant respiratory disease excluding influenza
and pneumonia. None of these deviations is statistically significant. An
important point is that while the Enterline study noted fairly wide variations
in mortality ratios between plants, each with a relatively small number of
employees, the mortality ratios of the plants as a group were close to 100,
which is the expected statistical norm. The author has stated he does not
believe there is any evidence in his study of an excess in malignancies due to
man-made vitreous fiber in the plants he has studied to date.4"1
Another recent study by Robinson1*5 reported on a cohort of 595 workers
from just one of the rock wool plants included in the Enterline study. The
resulting standard mortality ratio for all causes of death was lower than the
adjusted United States population. The author suggested that lung cancer,
non-malignant respiratory disease and digestive cancer showed a progressive
rise related to time from first exposure. This was evident in workers exposed
for more than 30 years. However, there were no statistically significant
336
-------
excesses of malignant or non-malignant respiratory disease or digestive cancer
for the entire cohort. The numbers were extremely small and a careful examina-
tion of the data does not demonstrate any consistent pattern for malignant
respiratory disease, non-malignant respiratory disease or digestive cancer. The
healthy worker effect and the fact that smoking histories were not considered
also must be kept in mind when interpreting the data. The Enterline study,
encompassing a much larger group of workers, is more pertinent and indicates
no significant excess for these causes of death.
Very recently a report1*6 has been received on a retrospective cohort
study of 6536 fibrous glass production workers—all from one company but in
multiple plants—who worked 10 or more years with some portion of that employ-
ment between 1968 and 1977. A special component of this investigation was an
analysis of a long term cohort of 1240 individuals with 20 or more years of
employment and 30 or more years latency.
Analysis of the data reveals that for any cause of death there was no
marked excess or statistically significant increase in mortality. In fact,
the pattern of mortality for fibrous glass production workers appears con-
siderably lower than comparable U.S. patterns. Long-term workers enjoyed
an even more favorable mortality experience than those employed for shorter
periods.
SUMMARY
1. Asbestos fibers and man-made vitreous fibers differ in durability,
fate and ability to cause disease. In man, asbestos is known to
cause both malignant and non-malignant disease. In man, there is
no credible evidence of malignant or chronic progressive non-malignant
disease resulting from exposure to man-made vitreous fibers.
2. Airborne exposures of man-made vitreous fibers observed during
manufacture, fabrication and installation are extremely low, with
few exceptions, well below 1 fiber per milliliter.
3. No chronic progressive disease, either malignant or non-malignant,
has been demonstrated to date by inhalation of man-made vitreous
fibers in animal studies. Animal models demonstrate disease only
as a result of unnatural exposure to long thin fiber (less than
1.5 microns in diameter and greater than 10 microns long) by
surgical implantation (mesothelioma) and by intratracheal injection
(fibrosis).
REFERENCES
1. Wright, G. and M. Kuschner. The Influence of Varying Lengths of Glass
and Asbestos Fibers on Tissue Response in Guinea Pigs. Inhaled Particles
IV. Edited by W. H. Walton. Pergamon Press, Oxford and New York,
pp. 455-474, 1977.
2. Pooley, F. D. Electron Microscope Characteristics of Inhaled Chrysotile
Asbestos Fiber. British Journal of Industrial Medicine. 29:146-153, 1972.
337
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3. Assuncao, J. and M. Corn. The Effects of Milling on Diameters and Lengths
of Fibrous Glass and Chrysotile Asbestos Fibers. American Industrial
Hygiene Association Journal, pp. 811-819, 1975.
4. Smith, H. V. History, Processes, and Operations in the Manufacturing
and Uses of Fibrous Glass — One Company's Experience. In Occupational
Exposure to Fibrous Glass — Proceedings of a Symposium, HEW Publication
No. (NIOSH) 76-151, pp. 19-26, 1976.
5. Dement, J. M. Environmental Aspects of Fibrous Glass Production and
Utilization. Environmental Jlesearch, 9:295-312, 1975.
6. Esmen, N., et al. Summary of Measurements of Employee Exposure to Air-
borne Dust and Fiber in Sixteen Facilities Producing Man-Made Mineral
Fibers. American Industrial Hygiene Association Journal, 40:108-117,
1979.
7. Esmen, N., et al. Estimation of Employee Exposure to Total Suspended
Particulate Matter and Airborne Fibers in Insulation Installation Opera-
tions. A Report to the Thermal Insulation Manufacturers Association,
1980.
8. Gross, P., et al. The Pulmonary Reaction to High Concentrations of
Fibrous Glass Dust. Archives of Environmental Health, 20:696-704, 1970.
9. Botham, S. K. and P. F. Holt. The Development of Glass Fiber Bodies
in the Lungs of Guinea Pigs. Journal of Pathology, 103:149-156, 1971.
10. Tlmbrell, V. The Inhalation of Fibrous Dust. Annals of the New York
Academy of Sciences. 132:255-273, 1965.
11. Harris, R. L. Aerodynamic Considerations: What is a Respirable Fiber
of Fibrous Glass? In Occupational Exposure to Fibrous Glass — Proceedings
of a Symposium, HEW Publication No. (NIOSH) 76-151, pp. 51-56, 1976.
12. Harris, R. L. and D. A. Fraser. A Model for the Deposition of Fibers
in the Human Respiratory System. American Industrial Hygiene Associa-
tion Journal, 37:73-89, 1976.
13. Lippman, M., et al. Deposition of Fibrous Glass in the Human Respiratory
Tract. In Occupational Exposure to Fibrous Glass — Proceedings of a
Symposium, HEW Publication No. (NIOSH) 76-151, pp. 57-61, 1976.
14. Brain, J. D., et al. Pulmonary Distribution of Particles Given by
Intratracheal Instillation or by Aerosol Inhalation. Environmental
Research, 11:13-33, 1976.
15. Wagner, J. C. MRC Pneumoconiosis Unit of Llandough Hospital, Penarth
United Kingdom, to Dr. Paul Kotin, Senior Vice President of Health,
Safety and Environment for Johns-Manville Corporation: letter dated
April 17, 1980.
338
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16. Stanton, M. F. and C. Wrench. Mechanisms of Mesothelioma Induction With
Asbestos and Fibrous Glass. Journal of the National Cancer Institute,
48:797-821, 1972.
17. Stanton, M. F.t et al. Carcinogenicity of Fibrous Glass: Pleural
Response in the Rat in Relation to Fiber Dimension. Journal of the
National Cancer Institute, 58:587-597, 1977.
18. Pott, F. Some Aspects on the Dosimetry of the Carcinogenic Potency of
Asbestos and Other Fibrous Dusts. Staub-Reinhalt, 38:486-490, 1978,
(translation).
19. Wagner, J. C., et al. Mesotheliomata in Rats After Inoculation with
Asbestos and Other Materials. British Journal of Cancer, 28:173-185,
1973.
20. Wagner, J. C., et al. Studies of the Carcinogenic Effects of Fiber Glass
on Different Diameters Following Intrapleural Inoculation in Experimental
Animals. In Occupational Exposure to Fibrous Glass — Proceedings of a
Symposium, HEW Publication No. (NIOSH) 76-151, pp. 193-197, 1976.
21. Stanton, M. F., et al. Experimental Pulmonary Carcinogenesis with
Asbestos. American Industrial Hygiene Association Journal, 30:236-244,
1969.
22. Richards, R. J. and T. G. Morris. Collagen and Mucopolysaccharide
Production in Growing Lung Fibroblasts Exposed to Chrysotile Asbestos.
Life Sciences, 12(II):441-451, 1973.
23. Brown, R. C., et al. In Vitro Biological Effects of Glass Fibers.
Journal of Environmental Pathology and Toxicology, 2:1369-1383, 1979.
24. Wright, G. Airborne Fibrous Glass Particles. Archives of Environmental
Health, 16:175-181, 1968.
25. Utldjian, H. M. D. and R. T. P. deTreville. Fibrous Glass Manufacturing
and Health — Report of an Epidemiological Study, Part I. Industrial
Health Foundation Transactions of the 35th Annual Meeting, 1970.
26. deTreville, R. T. P., et al. Fibrous Glass Manufacturing and Health —
Results of a Comprehensive Physiological Study: Part II. Industrial
Health Foundation Transactions of the 35th Annual Meeting, 1970.
27. Nasr, N. M., et al. The Prevalence of Radiographic Abnormalities in the
Chests of Fiber Glass Workers. Journal of Occupational Medicine, 13:
371-376, 1971.
28. Hill, H. W., et al. Glass Fibres: Absence of Pulmonary Hazard in
Production Workers. British Journal of Industrial Medicine, 30:174-179,
1973.
339
-------
29. Gross, P., et al. Lungs of Workers Exposed to Fiber Glass. Archives of
Environmental Health, 23:67-76, 1971.
30. Champeix, J. Fiberglass Pathology and Hygiene of Factories. Arch
Maladies Profess. 6:91-94 (1944) (translation).
31. Roche, L. The Pulmonary Hazards in the Glass Fiber Industry. Arch
Maladies Profess. 7:27-28 (1946) (translation).
32. Cirla, P. Occupational Pathology from Spun Glass. Med Lavoro, 39:152-157,
(1948) (translation).
33. Mungo, A. Pathology From Processing Glass Wool Stratified Materials.
Folia Medica, 43:962-970 (1960) (translation).
34. Milby, T. H. and C. R. Wolf. Respiratory Tract Irritation From Fibrous
Glass Inhalation. Journal of Occupational Medicine, 11:409-410 (1969).
35. Siebert, W. J. Fiberglass Health Hazard Investigation. Industrial
Medicine, 11:6-9, 1942.
36. Sulzberger, M. B. and R. Baer. The Effects of Fiberglas on Animal
and Human Skin. Industrial Medicine, 11:482-484, 1942.
37. Heisel, E. B. and J. H. Mitchell. Cutaneous Reaction to Fiberglas,
Industrial Medicine and Surgery, 26:547-550, 1957.
38. Heisel, E. B. and F. E. Hunt. Further Studies in Cutaneous Reactions
to Glass Fibers. Archives of Environmental Health, 17:705-711, 1968.
39. Fossick, P. A., et al. Fibrous Glass Dermatitis. American Industrial
Hygiene Association Journal, pp. 12-15, 1970.
40. Bayliss, D. L., et al. Mortality Patterns Among Fibrous Glass Production
Workers. Annals of the New York Academy of Sciences, 271:324-335, 1976.
41. Konzen, J. L. Comments on Mortality Patterns Among Fibrous Glass
Production Workers. U.S. Department of Commerce, National Technical
Information Service No. PB-257-784, 1976.
42. Bayliss, D. L., et al. Rebuttal to Comments by J. L. Konzen, M. D. on
the manuscript entitled, Mortality Patterns Among Fibrous Glass Produc-
tion Workers. U.S. Department of Commerce, National Technical Informa-
tion Service No. PB-257-784, 1976.
43. Enterline, P. E. and G. M. Marsh. Final Report on Part One of Mortality
Among Man-Made Mineral Fiber Workers in the United States, submitted to
the Medical and Scientific Committee of the Thermal Insulation Manu-
facturers Association, 1979.
340
-------
44. Enterline, P. E.f Professor and •Chairman, Department of Blostatistics of
the University of Pittsburgh, to J. W. Hill, M.D., Medical Director,
Pilkington Brothers Limited, St. Helens, England, (letter dated
April 9, 1980).
45. Robinson, C. F., et al. Mortality Patterns of Rock and Slag Mineral Wool
Production Workers, presented at the National Institute of Occupational
Safety and Health Symposium in Rockville, Maryland, 1979.
46. Morgan, Robert W., et al. Mortality Study of Owens-Corning Fiberglas
Production Workers. Report prepared by SRI, International for Owens-
Corning Fiberglas Corporation, 1980.
341
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DISCUSSION ON MAN-MADE VITREOUS FIBERS
QUESTION (Dr. Cooper): You did not mention mesothelioma in your epidemiologic
studies and I am sure no mesothelioma occured in any of these popu-
lations. I would have thought the absence of them would have been
noteworthy also.
ANSWER (Dr. Konzen): The data made no mention of mesothelioma.
342
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THE TRANSLOCATION AND FATE OF SIZED MAN-MADE MINERAL FIBERS
FOLLOWING EXPOSURE BY INTRATRACHEAL INSTILLATION IN RATS
by
David M. Bernstein, Ph.D., Robert T. Drew, Ph.D., and Marvin Kuschner, M.D.*
Medical Department
Brookhaven National Laboratory
Upton, New York 11973
and
Pathology Department
Health Sciences Center
State University of New York at Stony Brook
Stony Brook, New York 11794
ABSTRACT
A number of studies have suggested that both the length and diameter of
glass fibers are important parameters in determining their deposition and
translocation in the lung and in the subsequent pathological response by the
lung. However, the fibers used in these previous studies had broad size distri-
butions and were often administered in a highly artificial manner. To better
characterize the biological response to glass fibers, a study is being con-
ducted to determine the translocation and ultimate fate of fibers of defined
sizes after introduction into the respiratory tract of rats by both instil-
lation and inhalation. The fibers have geometric mean diameters of 1.5 vim
(ag = 1.11) and lengths of either 5ym (ag = 1.49) or 60 ym (ag = 3.76).
Serial sacrifices following intratracheal instillation of either 2 mg or 20
mg doses have shown differences in the response to the two sizes of fibers.
The short fibers are found primarily within mononuclear phagocytes in both the
lung and regional lymph nodes. The majority of long fibers, however, cannot
be totally engulfed by macrophages, nor are they cleared to the regional lymph
nodes, although smaller fragments accompanying the long fibers may be so
cleared. The long fibers produce a striking foreign body reaction in the lung,
particularly when impacted in the bronchi.
A "trachea only" inhalation method was used to expose rats to approximately
500 fibers/cc for one hour, resulting in the deposition of 30,000 to 50,000
fibers in the lungs of each rat. Serial sacrifices at intervals similar to
those in the instillation study will permit comparison of the biological
response following these two methods of administration.
*Presented by David II. Bernstein, Ph.D.
343
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INTRODUCTION
The length and diameter of glass fibers determine not only their deposi-
tion in the lung !»2 through inhalation but are also thought to be important
factors in fiber translocation and subsequent pathological response.3 Stan-
ton and Wrench4 demonstrated that when placed directly into the pleural
cavity of rats, glass fibers are associated with the development of mesothe-
lioma. It remains unclear whether glass fibers actually reach the pleural
cavity when administered in a less artificial manner through the tracheo-
bronchial tree. In the past, resolving the relationship of fiber size to
these effects has been compounded by the difficulty in separating different
lengths of fibers of the same diameter. Using fibers manufactured to
specified size distributions, this study has examined the deposition, translo-
cation, and fate of glass fibers after introduction into the respiratory tract
of rats.
Three routes of exposure were initially considered; intratracheal
instillation of aqueous suspension, nose only inhalation exposure, and insuf-
flation of a very thick air suspension of fibers. The intratracheal instill-
ation provided a means of administering large quantities of fibers into the
lung with relative ease. Rats are obligatory nose breathers and when inhaled
through the nose the majority of the long fibers used in this study were
found to deposit in the tortuous nasopharyngeal region of the rat. Hence, a
trachea only inhalation exposure method was developed to expose animals to
fiber aerosols. With the successful development of the trachea only inhala-
tion methodology, insufflation of very thick air suspensions of fibers was
not pursued further.
This report reviews the methods and techniques developed for exposure by
intratracheal instillation, presents the glass fiber clearance data, and
summarizes the histological findings through six months post exposure.
MATERIALS AND METHODS
The fibers were manufactured to either 1.5 x 5ym or 1.5 x 60 urn in size5.
The length distribution of each group of fibers is shown in Figure 1 with the
short fibers having a geometric mean length of 5.1 urn (SD = 1.49) and the
long fibers a geometric mean length of 54 ym (SD = 3.76). Scanning electron
micrographs of the fibers are shown in Figures 2 and 3. The fibers were
neutron activated and ZN^5 determined to be the best tracer nuclide to allow
quantification of deposition and clearance of the fibers in vivo.5
Animals
These studies were conducted with male Fisher 344 rats purchased from
Charles River. The exposures were begun when the animals were approximately
15 weeks old. They were housed in wire cages, allowed food and water ad li-
bitum, and maintained on a 12 hr light cycle at 22 ± 2°C, 50 percent relative
humidity.
344
-------
CO
4S
Ui
o
2
LJ
Z>
O
LU
30 40 50 60 70 80 90
10
FIBER LENGTH (/im)
Figure 1. Length distribution of each group of fibers.
-------
Figure 2.
347
-------
Figure 3.
349
-------
Intratracheal Instillation
The techniques for intratracheal instillation of the glass fibers have
been described earlier5. Thirty rats per group were instilled with either
1.5 x 60 van (Group 1) or 1.5 x 5 vim fibers (Groups 2 and 3) that were tagged
by activation as outlined in Table 1. Rats in Group 2 were instilled with
approximately the same number of fibers as rats in Group 1 and rats in Group
3 were given the same weight of fiberglass as rats in Group 1. Since the
fiber concentration administered to each rat was determined by radioassay
immediately after exposure, only 15 rats could be instilled on any given day.
With this limitation and the necessity to radioassay the groups at the same
time intervals following exposure, the instillation protocol shown in Table 1
was developed.
In addition, 50 rats/group were exposed to non-activated (or cold) fibers
to insure that potential long term effects were t£e result of the glass fibers
and not the small amount of radioactivity present. This number of animals
was chosen from statistical considerations to permit detection of a two
tumor difference between the activated and non-activated exposure groups at the
end of two years.
Necropsy
The rats were sacrificed by pentabarbital anesthesia with exsanguination
through the descending aorta. The lungs were then perfused in situ with
heparinized isotonic saline through the pulmonary artery, removed, and inflated
with glutaraldehyde vapor using an endotracheal tube (at a pressure of 20 cm
water); and then infused with glutaraldehyde fixative through the pulmonary
vasculature (at a pressure of 20 cm water).
After the lungs were fixed, the hilar lymph nodes, thymus, and adipose
tissue were dissected away. In addition, the diaphragm, gastrointestinal
tract, liver, spleen, kidney, brain, and femur were removed for histological
examination.
Tissues were embedded in parafin, sectioned (at a thickness of 10 urn),
mounted on glass slides, and stained with either hemotoxylin and eosin (H&E),
reticulum, or trichrome stains. Histoclad mounting media was used for all
sections.
Microscopy
The standard histological sections were viewed by light microscopy for
histopathological evaluation and by a pseudo-dark field technique for evaluation
of glass fiber numbers and location in the tissue sections. In addition,
scanning electron microscopy was performed on fixed tissues prepared by a
critical point drying technique. The size distributions of the glass fibers
were determined by microscopic measurement with the aid of a Zeiss MOP-3
image analyzer.
350
-------
TABLE 1. FIBER GLASS INSTILLATION SCHEDULE*
Exposure
Group
Group I
Group II
Group III
Group IV
Fiber Size
and Dose
1.5 x 60 ym
20 mg
1.5 x 5 ym
2 mg
1.5 x 5 ym
20 mg
Saline
Control
Number of
Rats Instilled
14
16
14
17
15
15
15
15
Date of
Instillation
2/26/79
2/28/79
3/26/79
3/28/79
3/12/79
3/14/79
4/9/79
4/11/79
*
The instillation schedule was staggered as shown to
permit radioassay of each rat following exposure.
TABLE 2. FIBER CONCENTRATION
Exposure
Group
20 mg
1.5 x 60 ym
2 mg
1.5 x 5 ym
20 mg
1.5 x 5 ym
N
21
24
22
Mean
0.15
0.09
0.18
(Standard
Deviation)
(0.04)
(0.04)
(0.02)
Note: Fraction Remaining at ~300 days
after Exposure.
351
-------
RESULTS
Animal Weights
Rats were weighed in each group at equal intervals after exposure. Since
the time of exposure was offset as shown in Table 1 and the rats were all of
the same age when received, the weight curves were shifted reflecting this
temporal offset in exposure. The growth curves for each group were not signi-
ficantly different as determined by an F test on the slopes and shown by the
parallel curves in Figure 4.
Glass Fiber Clearance
The clearance of glass fibers from the rats was determined by in vivo
radioassay of each apical. It is important to note, however, that this tech-
nique only accounts for whole body clearance of fibers and is not sensitive to
translocation of fibers within the rat.
The clearance curves for each of the three exposure groups through ~300
days are shown in Figures 5, 6, and 7. The low dose short fiber clearance is
significantly different, P < 0.01, from either the long or short high dose
group (as determined by analysis of covariance). This is reflected in the
percent remaining at~300 days as shown in Table 2. If the data is evaluated
by a three component exponential model in terms of short, intermediate, and
long term phases of clearance (Table 3), significant differences (P ~ 0.01)
are noted in the short and intermediate phases of the two high dose groups.
Scanning Electron Micrographs
To examine the pulmonary response to the two types of fibers by electron
microscopy, rats instilled with 20 mg of either long or short fibers were
sacrificed two weeks after exposure. The lungs of rats exposed to long fibers
are shown in Figures 8 and 9. Macrophages attempting to phagocytize the long
fibers are readily noted (Figure 8). In addition, other areas are seen with
clumps of fibers present associated with a nodular densely aggregated cellular
response (Figure 9").
This is in contrast with the response to the short fibers seen in Figures
10 and 11. These short fibers are found in large numbers in macrophages and
for the most part are completely engulfed by these cells. Some fibers are
seen free in airspaces (Figure 11). The nodular aggregates noted with the
long fibers are not evident.
Histological Results
The histological results reported here are from the first serial sacrifice
at six months post exposure involving four animals /group. In addition, a few
animals died under anesthesia for the radioassay procedure. These animals
were sacrificed as described above and the histological results presented as
well. '
352
-------
MEAN RAT WEIGHTS
400
E 380
u>
g
H
5
360
340
EXPOSURE GROUP
..111 20mg - I.5x60/tm
___ 20 mg - I.
J17I 2mg - I.SxS/tm
SALINE CONTROL
INSTILLATION DATE
2/26/79
2/28/79
3/12/79
3/14/79
3/26/79
3/28/79
4/9/79
4/11/79
260 K
240-
..^•".-
i i
i i
1 I I
10 20 30 40 50 60 70 80 90 100 110 120 130 140 ISO 160 170 180
TIME (days) FROM INSTILLATION
190 200
Figure 4. Growth curves.
-------
I?
i
1.5 x 60 pm Expo.6u/z.e
20 wig I?o4e
29.1)0 50.00 TS.OO 100-00 IZS.OO IU-00 115.00 200.00 2».00 290-00 215.00 VD.OO S2S.U BO.OO
Figure 5. Clearance curve.
354
-------
£?
fc
7.5 x 5 ]im Expo4ote
2 mg
=1)00 n oo so.oo li.oo itm-oo in-oo iso-oo iis.oo no.m ns.oo TSO.DO ? 15.00 900-00 moo %o oo
IIM£IDB»Sl
Figure 6. Clearance curve.
355
-------
&
Is
fc
§*.
i
x 5 ym Expo-6ote
20 mg
t i
* •
I *
' ' ..•
*%.00 75-00 50.00 15.00 100.00 IH-OD IM4B ITt.OO 1094D HS-00 HO-OO 7B.OO 900.00 MS.OO 360.00
IM4B lit.
TinEIDRYSI
Figure 7. Clearance curve.
356
-------
TABLE 3. FIBER GLASS CLEARANCE
THREE COMPONENT EXPONENTIAL MODEL
Clearance half times (days)
Exposure
Group 1-10 days 11-60 days 61-300 days
20 mg
1.5 x 60 vm 20 58 173*
2 mg
1.5 x 5 vim
20 mg
1.5 * 5 ym
1A
29
43
63
115
173*
Not significantly different. All other half times
are significantly different from one another
(P < 0.01).
357
-------
Figure 8.
358
-------
Figure 9.
359
-------
Figure 10.
361
-------
Figure 11
-------
To illustrate the numbers and locations of fibers and their associations
with the histological observations, photographs for many of the light field H&E
stained sections are accompanied with a dark field image of the same field which
highlights the fibers. It should also be noted that with 10 ym sections of the
lung, it is likely that a 60 ym fiber would be cut in the sectioning process.
This, together with the fibers being somewhat randomly orientated in the lung
may give the appearance that the long fibers are somewhat shorter than 60 ym.
1.5 x 60 ym Fibers, 20 mg Exposure
At 4 days post-exposure a notable cellular response in association with
large numbers of fibers was observed (Figure 12). The initial stages of
granuloma formation were evident by 10 days (Figure 13), however, no giant
cells were observed. Many fibers were seen either free in the alveolar space
or in association with macrophages. By 40 days (Figure 14) the granulomas
were more defined and giant cells within these granulomata were easily seen.
Microscopic examination of the 6-month sacrifice of four rats/group
showed that the lungs contained numerous granulomata which were well developed,
containing epitheloid cells, giant cells, and large numbers of fibers (Figure
15). These granulomata were often peribronchiolar in orientation (Figure 16);
fairly uniformly distributed throughout the sections, and sharply demarcated at
their margins. Moderate numbers of fibers occurred singly or in small groups
outside the granulomata (Figure 17) often in the interstitum, however, rela-
tively few fibers were seen within the alveolar spaces. Hemosiderin was pre-
sent in association with the fibers. No 60 ym fibers were seen in the lymph
nodes although occasional smaller fibers or fragments or larger ones were
present (Figure 18).
1.5 x 5 ym Fibers, 2 mg Dose
No animals in this group died prior to the 6-month sacrifice.
At 6 months, animals exposed to 2 mg of the short fibers revealed a gen-
erally heterogenous distribution of the residual fibers throughout the pulmonary
tissue (Figure 19). There were few or no fibers in most areas. Where found,
the fibers were present in association with variable sized aggregates of mono-
nuclear cells, small groups of which often appeared to be interstitial (Figure
20). There were, however, some larger fiber-cell aggregates with components
that were within air spaces, air spaces now largely obscured by the abundance
of cells. The mononuclear aggregates were not arranged into structured granu-
lomata and no giant cells were present. Small amounts of hemosiderin were
found in association with fiber aggregates.
Lymph nodes were found to contain fibers occurring in dense aggregates of
macrophages. There was wide interanimal variability in the extent of lymph
node involvement and the size of lymph nodes within each exposure group.
1.5 x 5 ym Fibers, 20 mg Dose
%•
The lungs of the single animal that died at 40 days post-exposure showed
a similar but more intense response than that described below.
364
-------
Figure 12.
365
-------
Vtvik Field
Figure 13.
367
-------
Figure 14.
369
-------
'
Figure 15.
371
-------
Figure 16.
373
-------
Figure 17.
375
-------
Figure 18.
377
-------
'"*
* •'• ' "^
* . v*
*_1 _/ ' ' - , ,7 '
J'. A
•4
If A,"
if -^* •• '^>
-
*- '
'+.
^
^
V ' V*
Figure 19.
379
-------
Figure 20.
381
-------
Microscopic evaluation of the lungs of the animals from the 6-month sac-
rifice revealed a distinct, usually peribronchiolar granulomatous reaction to
fibers in some areas, while in other areas, fibers occurred in dense aggregates
in association with a relatively sparse cellular response. No giant cells were
seen within these granulomata. Fibers were clearly evident within interstitial
macrophages (Figure 21) and in some areas could be seen in alveolar macrophages
(Figure 22). In still other areas, lymphocytes rather than histiocytes were
the predominant cell type seen in relation to the fibers. Granulomata contain-
ing dense aggregates of fibers were seen in paratracheal lymphoid tissue (lymph
sumps) (Figure 23) . There appeared to be a 2 to 3 fold range in amount of
residual fiber and associated cellular reaction in this exposure category. In
the lymph nodes large numbers of fibers were seen in dense aggregates associated
with a granulomatous response (Figure 24). Again, there was a large amount of
interanimal variability in the extent of lymph node involvement and size of
lymph nodes.
DISCUSSION AND CONCLUSIONS
In both the 2 and 20 mg dose 1.5 x 5 ym exposure group, the fibers
appeared to lie primarily within mononuclear phagocytes in both the lung and
hilar lymph nodes. Engulfment of the fibers by the macrophages appeared to
take place for the majority of fibers within a few days after exposure. At
~300 days after exposure, 80 to 90 percent of the fibers were cleared from
the rats in both exposure groups, with a low dose (2 mg) short fiber group
having a significantly faster clearance than the high dose (20 mg) group.
In contrast, the majority of long fibers could not be totally engulfed
by macrophages, nor were they cleared to the regional lymph nodes, although
smaller fragments accompanying the long fibers were .so cleared. The long
fibers produced a striking foreign body reaction, particularly when impacted
in the bronchi.
The whole rat clearance curves for animals exposed to the long fiber
were different from those for the animals exposed to the short fiber only
in the early stages of clearance (<60 days). The majority of both types of
fibers were thought to be cleared by way of the mucociliary escalator,
however, short fibers were also translocated to the lymph nodes while long
fibers did not reach the lymph nodes in significant numbers. Instead, long
fibers appeared to be found in foreign body type granulomas. While these
differences were apparent from the histological findings the clearance
curves were not sensitive to fiber translocations within the rat.
Aggregation of the glass fibers and the consequent impaction of the
fibers in the airways seems unavoidable with the single 20 mg dose adminis-
tered. To circumvent this, another group of rats are currently being ex-
posed to much lower doses of sized fibers by intratracheal instillation
repeatedly over several weeks. Comparison of the fiber distribution in the
lungs from these two studies as well as the distribution from the inhalation
study will help evaluate the validity of these exposures.
382
-------
Figure 21.
383
-------
Figure 22,
385
-------
Figure 23.
387
-------
Figure 24.
389
-------
While there are clear differences in the pulmonary response to the diff-
erent size fibers, there is no evidence, thus far, to indicate that either
type of fiber produces fibrosis. These studies are continuing, however, with
serial sacrifices of four rats/group scheduled at 6-month intervals.
ACKNOWLEDGEMENTS
The authors wish to thank Mr. Robert Peck, Ms. Mar tine O'Connor, and Ms.
Patricia Carr for the analytical and necropsy work and Mr. Charles Bores for
data management and computer data processing.
We would also like to thank Dr. Philip Kane for the microscopic evaluation
of the histological slides, and Mr. George Schidlovsky for the scanning electron
microscopy.
This work is supported by the Thermal Insulation Manufacturers Association
and the United States Department of Energy under Contract No. DE-AC02-76CH00016.
REFERENCES
1. Harris, R. L., Jr., and V. Timbrell. The Influence of Fiber Shape in
Lung Deposition - Mathematical Estimates, In Inhaled Particles IV,
W. H. Walton, Ed., Pergamon Press, England (1977).
2. Timbrell, V. The Inhalation of Fibrous Dusts, Ann. N.Y. Acad. Sci. 132,
255-273 (1965).
3. Wright, G. W. and M. Kuschner. The Influence of Varying Lengths of Glass
and Asbestos Fibers on Tissue-Response in Guinea Pigs, In Inhaled Particles
IV, W. H. Walton, Ed., Pergamon Press, England (1977).
4. Stanton, M. F. and C. Wrench. Mechanisms of Mesothelioma Induction with
Asbestos and Fibrous Glass. J. Nat Cancer Inst. 48:797-821, (1972).
5. Bernstein, D. M., M. Kuschner, R. T. Drew. Experimental Approaches for
Exposure to Sized Glass Fibers, Envir. Health Persp. 34:47-57 (1980).
390
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DISCUSSION ON THE TRANSLOCATION AND FATE OF SIZED MAN-MADE
MINERAL FIBERS
QUESTION (Unidentified): I am from the Industrial Health Foundation.
I would like to ask a few questions and make a few comments.
I was very impressed by the parabolic curve that you showed of
clearance. That was about a 300-day curve?
ANSWER
(Dr. Bernstein): Yes, it was.
QUESTION (Unidentified): And was it similar in the long fibers as in the
short fibers?
ANSWER (Dr. Bernstein): For the high dose groups it was as if you
looked at the whole curve together. If you break it down into
different clearance regions there were differences between the
long and short fibers in the early stages and not in the later
stages.
REMARK (Unidentified): The conclusion that I would draw from the
character of those clearance curves is that the fibers were not
imprisoned in a very tight manner over the 300-day period.
QUESTION (Dr. Bernstein): Which fibers?
ANSWER (Unidentified): The long and short. The short fibers certainly
were not and the long fibers, according to the character of the
curve, showed very little residue at the end of 300 days. The
clearance was pretty good compared to the curves that one sees in
intfatracheal injection of silica, for example, where the
injected silica particles are fairly tightly imprisoned within the
silicotic nodules. There is an important difference here and it
probably reflects the lack of collagenous tissue reaction in the
nodules. It reflects the failure of the glass fibers to evoke a
fibrotic reaction.
REMARK (Dr. Bernstein): It is clear from our analysis of the histological
sections that at six months, there is certainly no fibrotic
reaction.
QUESTION (Unidentified): Did you note a significant difference in the size
of the granulomas nodule at six months as compared to two weeks?
ANSWER (Dr. Bernstein): No, I did not. I did not do a statistical
measurement of it. It is only my own observation. I did not
notice it in that time period. It is our feeling that these are
not static lesions; that these lesions evolve, new macrophages
come in, old ones die and that these do evolve in some way or
another over a period of time.
391
-------
QUESTION (Unidentified): Did you do a similar study of the distribution of
injected glass fibers in the lung immediately after the injection?
ANSWER (Dr. Bernstein): Oh, yes. We looked at the distribution in the
lung immediately after injection, or a few hours after and it is
much more heterogeneous.
QUESTION (Unidentified): It is not a diffused distribution of the fibers, or
is it?
ANSWER
QUESTION
ANSWER
QUESTION
ANSWER
QUESTION
ANSWER:
REMARK
REMARK
QUESTION
(Dr. Bernstein):
look.
It is really a combination, depending where you
(Unidentified): Tou mean they are widely distributed?
(Dr. Bernstein): Well, it is varying degrees of fibers throughout
many areas of the lung.
(Unidentified): What I am pointing to is the statement that Drs.
Kuschner and Wright made about the guinea pigs when they indicated
that as a result of intratracheal injection, the glass fibers were
deposited in irregular manners, in heaps, at the points of bi-
furcation of the air passages rather than a diffused distribution
of fibers as one would expect when the materials are inhaled.
(Dr. Bernstein): Perhaps I can answer your question by saying that
the distribution we have seen in this study with one 20-milligram
exposure is different than what Wright and Kuschner saw and it is
also different than what one might expect by inhalation.
(Unidentified): Would you say that the difference between your rat
results and the guinea pig results in part result from a
difference in dosage?
(Dr. Bernstein): I would not like to compare it at this point. We
have our rat results for six months and the guinea pig results which
were carried out to the two year period of the experiment. At the
end of two years I would be better able to compare the two.
(Unidentified)t It seems to me that the important result that
you have demonstrated so far is that, at least at the six-month
period, there is no evidence of a fibrotic reaction to the pre-
sence of the glass fibers, but that there is a foreign body
reaction.
(Dr. Bernstein): That is definitely true and there is definitely
a difference in the reaction of the long versus the short fibers
in this response.
(Unidentified): There are a couple of interesting findings here.
The glass fiber is a square cut off at the end. Ifc is not pointy,
in other words, and yet that did not prevent the fibers from
going through the phagocytes.
392
-------
ANSWER (Dr. Bernstein): Well, I do not know if the fibers went through
the phagocytes or the phagocytes tried to engulf the fibers.
QUESTION (Unidentified): Right. But the fibers seemed to be continuous
through the phagocyte?
ANSWER (Dr. Bernstein): Yes.
QUESTION (Unidentified): All right. Being cut off square did not prevent
this process from occurring?
ANSWER (Dr. Bernstein): Well, I do not know that a phagocyte knows
anything about being cut off square or how long the fiber is.
REMARK (Unidentified): I know, but this is important in terms of com-
paring one type of fibrous material and another type.
ANSWER (Dr. Bernstein): Well, they are not really square. The early
scanning pictures that I showed you in very high magnification
of the edges showed that they are fairly jagged. The macrophage
theoretically may see the end of the particle and say, hey, that
is a particle I can phagocytize, and then try to do it. It may
see the diameter when it comes in head-on perpendicular to the
fiber and say, yes, I can phagocytize that too. It does not
know that it cannot, by the mechanisms of information that is
transmitted to the macrophage. It seems that when you have
fibers of too large a diameter the macrophage does not try to
engulf it. It knows it cannot in a sense.
REMARK (Unidentified): You point out also in the abstract that the
long fibers are found in the pleural cavity but the short
fibers are not.
ANSWER (Dr. Bernstein): I qualified that a little more carefully in my
talk by saying that this is a preliminary result. We have a more
elaborate study going on now to look at this in detail. The pre-
liminary results did Indicate this and the more elaborate results
will tell us more.
QUESTION (Unidentified): Will you be looking for the potential formation
of mesothelioma?
ANSWER (Dr. Bernstein): Yes. That is one of our end points.
REMARK (Mr. Ashford): I am from the Massachusetts Institute of
Technology.
I think Dr. Bernstein has been very careful in terms of stating
the limitations on what conclusions can be drawn from the data
and I would, just as a student of regulatory history, caution
you not to take great heart from the fact that the 6 month
data do not indicate a real problem. The reason I say this
393
-------
is, first, there will be some problems relative to the inhala-
tion characteristics which Dr. Bernstein has found, and second,
I do not think taking great heart in the science of this point
is going to do the industry very much good. It would be very
good to have alternative technologies in mind, changes in terms
of the fiber lengths that are produced by the fiberglass indus-
try and other issues rather than waiting until the data come
in and then act surprised. I just think that one has to be
careful when one views the preliminary results.
ANSWER (Dr. Bernstein): I would say that until the results are in
there is no way I can give an opinion as to what is going to be
happening.
QUESTION (Mr. Wright): I work for the Steel Workers Union in the Safety
and Health Department.
I have a technical question. I know your study did not concern
this problem but it is an interesting one. Have you or has
anyone else looked at the clearance of particles from the
silicated portion of the bronchial tree? The reason I am asking
that is to try to figure if there is any evidence indicating that
the lung's clearance mechanism for that portion might be less
efficient for long fibers than it is for shorter fibers or for
non-fibrous material.
ANSWER (Dr. Bernstein): Well, the only thing I can do is to give you a
comment based on the indirect measurements that we have looked at.
Those are in terms of whole rat clearance.
If one looks at the histological results and sees that there are
a fair number of short fibers going to the lymph nodes, that is
included in the whole rat measurement. When one looks at the long
fiber group and sees that very little is going to the lymph node
and not that many are going anywhere else, it seems that even
the silicated mucous transport mechanism is more efficient in
clearing the long fibers than the short fibers because the
clearance curves indicate approximately the same quantity left in
the rat at the end of 300 days.
394
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OCCUPATIONAL EXPOSURES
TO MINERAL WOOL
by
Mr. Douglas P. Fowler
Center for Community
Health Studies
SRI International
333 Ravenswood Avenue
Menlo Park, CA 94025
INTRODUCTION
The bulk of the work to be presented here was performed during the period
1976-1978 under Contract Number 210-76-0120 with the National Institute for
Occupational Safety and Health. In addition to the work performed for NIOSH,
substantial work has been undertaken in the U.S. by the Thermal Insulation
Manufacturer's Association (TIMA) and in Europe by the Joint European Re-
search Board (J.E.M.R.B.). This work will be briefly mentioned as well. The
readers interested in the general questions associated with man-made mineral
fibers in the environment should consult the review prepared by Corn (1979).
BACKGROUND
Mineral wool is a generic term that denotes any fibrous glassy substance
made from minerals (e.g., natural rock) or mineral products (e.g., slag or
glass). For the purpose of this presentation, mineral wool has been defined
to include only those fibers made from natural rock (rock wool) or from slag
(slag wool), thus fibrous glass is excluded.
•
Mineral wool has been produced and used for over a century. Thoenen
(1939) reported that mineral wool was first produced in Wales in 1840.
Production began shortly thereafter in Germany. The first U.S. mineral
wool plant began operation in Cleveland, Ohio in 1838. In 1890, a plant
was in operation in Salem, Virginia. The first successful commercial
production operation was started in 1897 by C. C. Hall in Alexandria,
Indiana. The product began to find a substantial market by the end of
the first world war (Pundsack, 1976). By 1939, there were 71 companies
operating 82 plants manufacturing slag, rock, and glass wool.
In the late 1930's Corning Glass Works and Owens-Illinois joined forces
to become Owens-Corning Fiberglas; and the company invested heavily in
technology to produce glass wool by processes superior to those that had
been used in the past. The paths of rock wool and glass wool partially
395
-------
diverged at this point—the rock wool and slag wool manufacturers continued
mainly with the processes and markets of the past, and the glass wool
manufacturers opened new markets, including textiles (Smith , 1976). How-
ever, the two products continued to compete in the thermal insulation market.
The basic process by which mineral wool is made today is similar to that
used in the 1890's. The raw material (slag and/or natural rock) is loaded
into a cupola in alternating layers with batches of coke and small amounts
of other raw materials used to give the fibers special characteristics of
ductility or size. The coke is burned, generating high temperatures and
melting the slag. The molten stream of slag issues from a hole in the
bottom of the cupola and is "fiberized." Currently, approximately 70 per-
cent of the mineral wool sold in the United States is produced from blast
furnace slag. A small amount is produced with natural rock, which is also
usually added to the slag to impart desired qualities of flexibility to the
fibers.
In the past, the usual practice was to direct a stream of steam (or
of air) to intercept the falling stream of slag, breaking it into many
small globules which then "tailed out", producing fibers with a semi-
spherical head. The heads broke off as the material cooled, producing
fibers and "shot" (the cooled heads).
Currently, most of the mineral wool in the United States is made by
variations of the Downey process. The stream of molten slag or rock falls
onto a spinning rotor and the partially fiberized slag or rock is further
attenuated by an annular stream of steam or air. The "dry spinning" process
is used by a minor fraction of the producers. This is a mechanical
attenuation process that does not use fluid attenuation for additional
separation.
As the fiber is formed, it may be further treated to increase its
utility for one or more of its intended uses. In general, these treatments
are applied immediately following the rotor, by the atomization of liquids
that are "sprayed" onto the newly formed fibers. In almost all cases, an
oil will be applied in this manner to reduce the "dustiness" (tendency to
become airborne) of the bulk products.
Where the mineral wool product to be produced is required to have
moderate or substantial structural rigidity or stability (as in equipment
insulation and building insulation batts and blankers), a "binder" (usually
a phenol formaldehyde resin) may be added immediately following or in place
of the oil treatment. The mineral wool may then be compressed into "batts",
"blankets" or "boards" or left loose as "wood".
Those products that are to be used without additional covering (such as
high-density equipment insulation and some residential insulation batts)
are packed for shipment. Other products require further covering, for
example, residential structural insulation is often covered with a vapor
barrier (e.g., Kraft paper treated with asphalt or aluminum foil) on one
side and untreated paper on the other side. For industrial insulation (e.g.,
boilers), a wire mesh covering is often added.
396
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MINERAL WOOL USE
Mineral wool is widely used in structural and industrial insulation pro-
ducts, as well as in cements, mortars, ceiling tiles, and other products
where its characteristics of thermal and structural stability are desirable.
The products in which mineral wool is used include:
• "Blowing" wool and "pouring" wool, loose bagged wool (either granu-
lated or not) that can be blown by pneumatic blowers or poured by
hand into residential or commercial building structural spaces.
• Batts and blankets, relatively loose and light (low density) material
shaped to file between structural members of residential or commercial
buildings.
• Cement, mortar, or ceiling tile. Producers of these1 products add
bulk fiber to their product to impart structural strength and
qualities of fire resistance and thermal and sound insulation.
• Industrial and commercial insulation products for covering pipes,
ducts, boilers and other equipment. High density material with
significant amounts of binder added.
• "Fireproofing" to be sprayed upon steel girders in buildings.
• Miscellaneous small volume uses; in friction materials, reinforced
plastics, etc.
Transportation costs are a significant fraction of the costs of insulation
products; to reduce these costs, the industry has become highly regionalized.
The most directly competitive product is fibrous glass.
In some areas of the U.S., mineral wool is the predominant mineral fiber
insulation material, while in others fibrous glass predominates. Because of
its greater density, mineral wool is a more effective sound insulator than
fibrous glass, and is thus often specified in industrial applications. However,
this greater density can be a drawback in the insulation of residential and
commercial structures, particularly where framing is light and the required
thermal insulation effectiveness is high.
Fibrous glass has steadily increased its share of the total insulation
market over the past 30 years. If the insulation market is examined in de-
tail, it can be seen that the most probable future market for mineral wool
is in the industrial sector, with relatively limited usage in residential and
commercial products. In general, the residential and commercial market frac-
tion for mineral wool is continuing to decline, with strength only in those
regions where it has marked economic advantages over fibrous glass. This
trend is expected to continue, with mineral wool consolidating its position
in the industrial market and gradually relinquishing part of its present
share of the commercial and residential insulation market. It may be expected
that mineral wool will find increasing use as a substitute for asbestos, as
asbestos is "phased out" of some industrial products because of its known
397
-------
adverse health effects. Thus, it may be expected that those workers who have
been exposed to asbestos in the past may in the future be exposed to mineral
wool fibers.
HEALTH EFFECTS OF MINERAL FIBER EXPOSURE
The health effects attributable to mineral fibers have been the subject
of major international conferences in the past 10 years (New York, 1964;
Dresden, 1968; Lyon, 1972). Other conferences such as the Johannesburg con-
ference in 1969 and the ILO Helsinki conference in 1971 have also devoted
substantial portions of time to the same and associated topics.
The majority of these reports, however, deal with only one category of
mineral fibers, asbestos. [We will set aside, for the moment, Harington's
(1975) objection to the use of "mineral fiber" as a generic term to include
the amorphous man-made fibers.] Little attention has been paid to the health
effects of other mineral fibers with the exception of limited work on fibrous
glass.
Health Effects of Asbestos
Cancer—
The most serious potential consequence of mineral fiber exposure is the
development of cancer. An increased incidence of the following tumors has
been associated with human exposure to asbestos:
Tumor Selected Epidemiologic Evidence
Lung Cancer (Doll, 1955; Knox, 1968; Selikoff,
1973)
Mesothelioma (Bohlig, 1973; Newhouse, 1973)
(Pleural & Peritoneal)
G.I. Cancer (Selikoff, 1973)
Laryngeal Cancer (Stell, 1973; Newhouse and Berry,
1973)
Fibrotic Lung Disease (Asbestosis)—
There is no need for further documentation of asbestosis in humans; such
documentation exists in scores of studies. Although the attack rates have
varied from study to study (and for type of asbestos fiber), it is clear
that inhalation of any form of asbestos will, given sufficient doses, lead
inevitably to asbestosis in a significant fraction of the exposed population.
The universality of the response can be seen in the table on pages 364-365
of Harington's (1975) review.
Health Effects of Fibrous Glass
% The only exposure-specific population studies that have been carried out
on the consequences of exposure to mineral fiber other than asbestos have
been on fibrous glass. The studies (Wright, 1968; Nasr, 1971; Utidjian, 1970;
398
-------
Gross, 1971) did not address the question of malignancy. They concluded from
pulmonary function (Utidjian), radiographic (Wright and Nasr), and post-
mortem (Gross) studies that there were no significant effects from occupational
exposure to fibrous glass. A discussion of these studies was presented in
an article by Dement (1975). A study by Enterline (1975) examined the mortal-
ity experience of a cohort of 416 men who retired during the period 1945-
1972 from six fibrous-glass manufacturing plants. Enterline found "no evi-
dence of an excess in respiratory cancer mortality. No mesotheliomas were
noted." For 115 of the men, the stated retirement cause was disability. Com-
paring this with the expected distribution, Enterline found "...no evidence
of any unusual health hazards, with the exception of a possible excess in
chronic bronchitis."
These and other studies were reviewed in-depth in the preparation of the
NIOSH Criteria Document on Fibrous Glass (NIOSH, 1977). Upon consideration
of human health studies and animal tests, NIOSH concluded that two categories
of fibrous glass could be defined—those fibers larger than 3.5 micrometers
(ym) diameter and those less than 3.5 ym. For the former, it was concluded:
The primary health effects associated with the larger diameter
fibers involve skin, eye, and upper respiratory tract irritation,
a relatively low incidence of .fibrotic (lung) changes, and
preliminary indication of a slight excess mortality risk due to
non-malignant respiratory diseases. In this regard, NIOSH
considers the health hazard potential of fibrous glass to be
greater than that of nuisance dust, but less than that of coal
dust or quartz.
The Criteria Document goes on to address the potential problems asso-
ciated with small diameter fibers. The laboratory animal implantation studies
of Stanton (1972, 1977) were examined and it was concluded that these results
could not be extrapolated directly to conditions of human exposure. The
document continued:
On the basis of currently available information, NIOSH does not
consider fibrous glass to be a substance that produces cancers as
a result of occupational exposure. However, these smaller fibers
can penetrate more deeply into the lungs than larger fibers and
until more definitive information is available, the possibility
of potentially hazardous effects warrants special consideration.
On the basis of these considerations, NIOSH recommended an environmental
(workplace air) concentration limit of 3 fibers/cm3, determined as a time-
weighted average concentration for up to a 10-hour work shift in a 40-hour
work week. Only those fibers with a diameter less than or equal to 3.5 ym
and a length equal to or greater than 10 ym are covered by the recommended
limit. Additional recommendations involve medical examinations and record
keeping.
399
-------
Health Effects of Mineral Wool
It has been assumed previously that fibrous glass and rock (or slag)
wool could be appropriately grouped together in a discussion of the health
effects of mineral fibers.. No reported studies of those exposed only to
rock wool or slag wool are known, although Enterline is currently carrying
out such a study, sponsored by the Thermal Insulation Manufacturers Associa-
tion (TIMA), (Konzen, 1980), as is NIOSH (Ness, 1979). No firm evidence
exists from which the health effects of rock wool or slag wool can be pre-
dicted. The evidence most clearly indicating potential exposure risks asso-
ciated with mineral wool is the work of Stanton et al. {1972, 1977), Kuschner
and Wright (1976), Pott et al. (1976) and Davis (1972). In these laboratory
studies, it has been found that long (& 10 ym) , thin (4, 1 ym) fibers have
greater biological potency (tumorigenicity, fibrogenicity) than shorter or
thicker fibers, regardless of the chemical composition of the fibers. This
indicates that these long, thin fibers are probably of greatest concern in
human exposures to mineral wool. Figure 1 is an adaption of some of Stanton's
data, showing the effect of increasing the fraction of long, thin fibers in
implanted fibers on the probability of tumor response in animals (Stanton, 1977)
Comparability of Results for Other Fibers: Extrapolation to Mineral Wool
There is convincing epidemiological and case report evidence that asbes-
tos, upon inhalation, is fibrogenic and carcinogenic in man. Fortunately,
no such convincing human evidence exists for other mineral fibers. It is
difficult to extrapolate from the results for asbestos to predict human health
effects from exposure to mineral wool. The work that has been done with
fibrous glass is more directly applicable, but there are still many areas of
uncertainty. The NIOSH decision (in regard to the recommended environmental
standard for fibrous glass) that "...until more information is available,
the recommended standard can also be applied to other man-made mineral
fibers..." seems appropriate with respect to mineral wool. The two recent
NIOSH publications (1976, 1977) dealing with fibrous glass are recommended
as background reading on the health effects of mineral wool, as are the
Copenhagen Workshop Proceedings (JEMRB, 1977).
One aspect of the potential problem associated with the human exposure
to this material has been a suggested demand for small fiber diameter.
Figure 2 shows the effect on bulk thermal conductivity (the inverse of insu-
lation effectiveness) of fiber diameter in these products. Because of the
costs associated with attaining smaller fiber diameters, most U.S. commercial
products, particularly those used in home insulation, have a median fiber
diameter near 4-5 ym. In Europe, however, and particularly in the Soviet
Union, mineral wool fibers are being commercially produced with median fiber
diameters
-------
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PARTICLE SIZE RANGE (UM)
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60
70
80
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*Adapted from Stanton, 1977.
-------
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FIBER DIAMETER. Mf"
Figure 2. Thermal conductivity as a function of fiber diameter.
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ULK S
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r» nn
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: -,t
MPUE U-B (193(1 "!" •"" '" "- '"
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2.0 6.0 tO.O 20.0 30.0 0.4 0.6 1.0 2.0 60 10.0 20.0 30.0
FIBER DIAMETER £m FIBER DIAMETER «rn
Figure 3. Frequency of occurrence of fibers of specific diameter in mineral wool samples.
-------
shown are not asbestos. Admixture of asbestos with other insulation materials
was apparently practiced from time to time in the past. In addition, the
producers and users of mineral wool products also commonly produced and used
asbestos-containing products, and exposures were mixed. Asbestos exposure
is thus a confounding variable in assessment of health effects due to expo-
sures to mineral wool in the past.
PRIOR STUDIES OF OCCUPATIONAL EXPOSURES
Human exposures to mineral wool fibers have been examined only in a few
studies. In the first of these, by Carpenter and Spolyar (1945), dust con-
centrations in a mineral wool production plant were measured by Greenburg-
Smith impingers in 1934. The dust counts so measured ranged from 12-26
million particles per cubic foot (mppcf) with limited dust control equipment
installed. When more effective controls had been installed, a resurvey by the
same investigators found dust concentrations of 5-10 mppcf.
In 1962, Sheinbaum reported the preliminary results of surveys in the
building trades, including the application of "asbestos-rockwool cement" as
a fireproofing and sound insulation agent. He found "extremely dusty con-
ditions," with average breathing zone impinger dust counts "about 200 mppcf."
Both of the above studies share a major disadvantage—the method of meas-
urement does not differentiate between mineral wool fibers and general partic-
ulate material. Thus, it is difficult to ascertain how much of the inhalation
burden imposed upon the workers in these operations resulted from mineral wool
fibers and how much resulted from other material. Total particulate mass
concentrations and fiber size were not determined in the above studies.
In 1976, Corn et al. published the results of extensive industrial hygiene
surveys in two mineral wool production plants. With the use of personal samp-
ling pumps, measurements were made of total suspended particulate matter con-
centrations and of fiber concentrations. The latter analysis was performed
with optical and electron microscopy, and the sizes of the fibers observed
were determined.
In Plant A, ceiling and wall panels and tiles containing about 50 percent
fiber were produced. Optically visible (>, 1 ym diameter) total fiber concen-
tration ranges were 0.2-1.4 fibers/cm3; electron microscopically visible
(£, 1 vim diameter) total fiber concentrations ranged from 0.0056-0.16 fibers/cm3.
Total suspended particulate material levels were 0.53-23.64 mg/m3.
In Plant B, where specialized thermal insulation materials were produced,
total suspended particulate matter levels were 0.045-6.88 mg/m3. Fibers
£, 1 vim (diameter) were found in concentrations from 0.11-0.43 fibers/cm3-
The concentrations of those fibers less than 1 ym diameter were 0.0059-0.089
fibers/cm3.
In both plants, the fraction of respirable fibers (less than 3 ym dia-
meter) was approximately 75 percent. The total airborne dust concentration
(mg/m3) was found to be a poor indicator of airborne fiber (fibers/cm3)
concentration.
404
-------
Esmen, et al. (1978) recently presented data upon the occupational expo-
sures In five mineral wool plants, including the two (mentioned above) dis-
cussed by Corn, et al. in 1976. Their general findings were that "the results
of the study indicate that the average exposure is about 0.1 to 0.5 fibers/ml.
The results also indicate that despite operational diversities among the
plants the size and length distributions of airborne fibers were consistent.
It was also found that there is an excellent correlation between average total
suspended particulate matter and average fiber exposure for types of work
activity found in the plants..." Although the last statement may appear to
conflict with their conclusion in the previous study, it should be noted that
they refer to excellent correlations of average concentrations as opposed to
poor correlations of individual (matched) concentrations in the previous work.
Recent European studies were discussed at a workshop in Copenhagen (JEMRB,
1976). It was stated in the discussion of those studies that "...concentrations
of fibers in the respirable range encountered in the production industry vary
between averages of about 0.03 and 0.2 fibers/ml" (Hill, 1977).
Schneider, in discussion of the mineral wool user industries in Scandi-
navia (1979), found that home insulation installers and industrial insulation
installers had the highest exposures among the user groups, with a few expo-
sures over 1 f/cm3. He found that optical microscopy was adequate for defini-
tion of exposure, which ranged from 0.05 to 3 fibers/cm3.
The National Institute for Occupational Safety and Health has engaged in
several studies that are now being presented. This report presents one such
study, and a NIOSH report on one ceiling title productions plant has recently
been presented, with information on an epidemiologic study of the workers at
that plant (Ness, 1979; Robinson, 1980).
In the investigation reported here, five production sites and six user
sites of mineral wool were selected for study, based upon the representative-
ness of the operations and the conditions of exposure of the workers in those
sites. Study methods included breathing-zone air sampling for airborne partic-
ulate material (total, fibrous, and respirable) with analyses to determine total
and respirable airborne particulate levels (gravimetric); airborne fiber con-
centrations and fiber size distributions (optical and scanning electron micro-
scopy); and airborne trace metals (atomic absorption). Limited evaluations
of worker exposure to carbon monoxide, heat, noise, and miscellaneous other
materials were performed in some site surveys. In addition to the environ-
mental evaluation, samples of bulk materials being produced and used were taken
for analysis. Analysis included optical microscopic determinations of fiber
diameter, determination of bulk sample elemental content by atomic absorption
(AA) and x-ray florescence (XRF), elemental analyses of separated fibrous and
compact particles by AA and XRF, and elemental analyses of individual particles
by x-ray microprobe.
In Tables 1 and 2, we show the general characteristics of the facilities
examined.
405
-------
TABLE 1. MINERAL WOOL PRODUCTION PLANTS SURVEYED
Raw materials
Years of production
Fiber- forming
process
Fiber
description
Products
produced
Worker
population
(Fiber production
and Maintenance)
Potential
exposures
Plants
A
Steel mill slag.
lead smelter slag
Coke, oil, PF rusln.
asphalt
28
Centrifugal
spinner with
steam attenuation
Slag wool
Bates, blowing
wool , and pouring
wool
100
Fibers, lead
fume. H2S,
PF resin, noise
B
Steel mill slag,
Iron ore, "phos-
phate" slag, coke,
PF resin, oil,
asphalt
29
Centrifugal
spinner with
steam attenuation
Slag wool
Batts, blowing
wool, pouring
wool, baled
wool
80
Fibers, combustion
products, HjS, CO,
PF resin, noise
C
Steel mill slag
rock
coke
maleic acid, oil
6
Dry spinner
(Powell process)
Slag wool
Blowing wool.
Baled wool
45
Fibers, combustion
products, metal fume,
maleic acid, noise
D
Iron smelter slag,
dolomite, quart zlte,
coke, oil
20
Centrifugal spinner
with steam attenuation
Slag wool
Calling tile
15
Fibers. CO,
combustion products
noise, general dust
E
Steel mill slag,
dolomite, PF resin,
coke, oil
50
Centrifugal spinner
with air attenuation
Slag wool
Industrial insulation .
blocks, blankets,
pipe covering
30
Fibers, noise
o
cr>
-------
TABLE 2. MINERAL WOOL USER FACILITIES SURVEYED
Facility
Product
usedj
|
Application
Processes
Worker
population
Years of
use
Potential
exposures
Bloving wool.
(Slag wool)
New house Insul-
ation
Blowing
4-10
15
Fibers, heat, CO
Blowing wool
(Slag wool)
Addition to
existing Insula-
tion
Blowing
4-10
45
Fibers, heat, CO,
settled house dust.
Industrial
blankets
(Slag wool)
Fabrication for
shipment
Facing with wire
•eah, packing
20
SO
Fibers
Bulk (slag wool)
wool
Production of
celling tiles
Mixing wool with
slurry, baking,
cutting, sanding,
painting, packing
tiles.
60
20
Fibers, clay, paint,
noise. •
Fireprooflng
Spray application
of fibrous fire-
proofing to
structural steel.
Pneumatic blowing
of dry fibrous mix,
wetted with spray
nozzle as applied.
2
10
Fibers, dust
Industrial blankets
Boiler Insulation
Facing with wire
mesh, application
of cement.
3
15
Fibers, dust,
noise
-------
Although the original report to NIOSH (Fowler, 1978) should be examined
for details, we will consider here a few of the points of interest in respect
to comparisons with asbestos, and present a summary of the findings.
Figure 4 is a presentation of the 95 percent confidence limits of the
geometric means of exposures to fibers, total particulate material, and
respirable particulate material in the producer and user facilities surveyed.
Also presented there is a comparison of the fiber sizes found in the eleven
facilities, by opt cal microscopy.
Figure 5 compares the fiber concentration found by optical microscopy,
with those found by scanning electron microscopy. As can be seen in those
two figures, the production workers had substantially lower exposure to all
forms of airborne particulate material than did the user workers.
Further, the user workers' exposure was to smaller fibers than was the
production workers' exposure. The difference in length can be seen in the
lower section of Figure 4, where the sizes of the fibers observed with the
optical microscope are shown. The difference in diameter of fibers to which
they are exposed between production workers and users is apparently slight.
However, as shown in Figure 5, examination of the samples with the scanning
electron microscope reveals substantially more fibers than does optical micro-
scopy. The mean concentration by electron microscopy in the 12 samples for
which both types of microscopy was applied is nearly four times the mean
determined by optical microscopy.
The phenomenon is not universal, however, and two examples are illus-
trative of the differences in exposure which may appear among users of mineral
wool. The first is the installation of "blowing wool" in attics. In this
job, two workers are usually employed. One of them opens bags of compressed
wool and empties the bags into a hopper from whence the wool is pneumatically
conveyed through a hose into the space to be insulated. The second worker
directs the blown wool into the space (usually an attic) to ensure adequate
depth and uniformity of coverage.
In the second example, the installation of sprayed fireproofing, two
workers are also employed. The first empties bagged fireproofing material
(a mixture of mineral wool, cement, and proprietary materials) into a hopper/
blower very similar to the device used for the installation of the blowing
wool. The mixture is also pneumatically conveyed to the second worker via
hose. At the point of exit from the hose, however, the blown cement mixture
is wetted by a water spray, and the wetted mixture is directed onto beams and
other structural members, to which it adheres.
The exposures within the two trades are shown in Table 3.
It is evident that the exposures are different. The blowing wool instal-
lers are exposed to substantially more small airborne particulate material
of all sorts than the sprayed fireproofing installers, even though the latter
are exposed to higher total airborne particulate material.
408
-------
FIBER
CONCENTRATIONS
(f/cc)
(optical microscopy)
PRODUCERS
USERS
IMHI
TOTAL
PARTICULATE
lm«/m3)
PRODUCERS
USERS
RESPIRABLE
PARTICULATE
(mg/m3)
PRODUCERS
USERS
0.1
1.0
f/cc or mg/m
FIBER SIZE bint)
1.0
10
2.0
AIRBORNE
FIBER
DIAMETER
AIRBORNE
FIBER
LENGTH
PRODUCERS
USERS
PRODUCERS
USERS
I
%
•
1
mti
20
Figure 4. Comparison of exposures of production and user facility workers.
409
-------
PRODUCTION WORKERS
42 SAMPLES
SEM
OM
USER WORKERS
12 SAMPLES
SEM
OM
I
0.1
0.2
0.6
f/ce
1.0
2.0
Figure 5. Comparison of confidence limits on geometric mean fiber
concentrations for samples examined by scanning electron
microscopy (SEM) and optical microscopy (OM).
410
-------
TABLE 3. COMPARISON OF MEAN EXPOSURES FOR SPRAYED FIREPROOFING
AND BLOWN INSULATION
Fibers/cc (O.M.)
Fiber s/cc (SEM)
Fiber Diameter (O.M.)
Fiber Length (O.M.)
Tot. Susp. Part. Matl.
Respirable Part. Matl.
Sprayed
Fireproofine
0.384 f/cc
0.217 f/cc
2.4 ym
35.3 ym
o
7.461 mg/m
0.370
Blown
Insulation
0.240 f/cc
3.09 f/cc
1.6 ym
12.0 ym
2.657 mg/m3
2.565 mg/m3
411
-------
Our general conclusions were that the production workers surveyed were
found to have relatively low exposures to all forms of airborne particulate
material, with few exceptions. The user workers had higher but more variable
exposures. It was generally not possible to separate exposure categories
on the basis of different exposures; there was significant overlap of the con-
fidence limits on mean exposure across the facilities surveyed.
Past exposures in this industry were probably higher than at present, and
asbestos exposure was relatively common.
In addition to exposures to airborne particulate material, exposures to
excessive noise levels were universal in the cupola areas of the production
plants. Heat stress was a potential problem for the installers of blown mineral
wool insulation.
Exposures to small diameter (<1.0 ym) fibers were not common, except in
the installation of blowing wool. In close installation situations, electron
microscopically visible airborne fibers were present in concentrations up to
ten times greater than optically visible fibers.
SRI's recommendations were that:
• The exposures of blowing wool installers to small fibers should be
evaluated further.
• The noise exposures of cupola operators should be evaluated, and
engineering solutions to this problem should be sought.
• The exposure of sprayed fireproofing workers to total airborne
particulate material are excessive, and suitable personal respira-
tory protection should be sought.
• Engineering measures to ameliorate the working conditions of the
blowing wool insulation installers should be sought for both the
worker in the attic, and the worker emptying bags into the hopper
(in the truck).
• Additional old samples should be sought to clearly identify
potential past exposures to small diameter fibers.
COMPARISON TO ASBESTOS EXPOSURES
Only two cases are known where mineral wool has been directly substi-
tuted for asbestos, and the potential occupational exposures subsequently
measured.
Reitze, et al. (1972) evaluated the exposures of sprayed fireproofing
installers to airborne asbestos fibers. The material and process used was
similar to that used in the installation described above, except that the
spray mixture contained substantial quantities of asbestos. The worker
emptying bags into the hopper was exposed to concentrations of asbestos
412
-------
fibers ranging from 5-22 fibers/cc (optical microscopically visible fibers
> 5 ym), and the nozzle operator was exposed to concentrations between 30-100
fibers/cc. These concentrations were more than 100 times greater than the
concentrations found in our study of the workers using a mineral wool based
mixture.
Balzer, et al., (1972) investigated the dust-producing potential of five
different thermal Insulation materials. Of these, one contained ~65 percent
asbestos, while another was comprised principally of mineral wool, and was
intended as a substitute for the first. The materials were treated by installa-
tion methods common in the field, but in a controlled environment. Fiber
counts and total dust were measured during each of several operations, includ-
ing hand sawing, scoring with a circular saw, band sawing, simulation of
application, simulation of pounding the. insulation into place, and a simula-
tion of tearout of old insulation.
The results are shown in Table 4.
The potential exposures to fibers from the product containing mineral
wool are substantially (10-40 times) lower than from the asbestos-containing
product. Total particulate material exposures varied. In some cases, the
exposure was higher, and in some cases lower, for the mineral wool product as
compared to the asbestos product.
From these two cases, it seems reasonable to tentatively conclude that
total exposure to fibrous particulate material can be reduced by the substi-
tution of mineral wool for asbestos in some products. Each case must be judged
individually, however, and the suitability of any proposed substitute must be
carefully guaged. Asbestos has been used in many widely-variant products
because of its unique physical characteristics. The wholesale-enforced sub-
stitution of mineral wool (or any other material) for asbestos may have serious
economic and technical repercussions. The entire life-cycle of each product
containing asbestos must be investigated before a decision to substitute is
made. The most suitable substitution must then be selected, based upon the
uses and available production technology for the specific product under
consideration.
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Safety and health in shipbuilding and ship repairing. International
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Bohlig, H., and E. Rain. 1973. Cancer in relation to environmental exposure.
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413
-------
TABLE 4. COMPAIRSON OF ASBESTOS AND MINERAL WOOL CONTAINING
INSULATION, AVERAGE DUST GENERATION
(Source: Balzer, et al., 1972)
OPERATION
Hand Sawing
Band Sawing
Scoring
Application
Pounding
Tearout
Total Particulate
Material (mg/m3)
A
12.6
89.8
159.8
7.9
2.3
26.4
B
3.9
58.6
345.8
3.1
3.4
62.9
Fiber Count
(F/cc)
A
57.3
376.2
2629.7
74.2
—
268.4
B
1.7
23.1
63.2
0.9
—
26.6
A - Asbestos
B - Mineral Wool
414
-------
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417
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DISCUSSION ON MINERAL WOOL
OUESTION (Mr. Dickinson): Arsenic occurs naturally with lead and copper.
Did you say that 30 percent of the rock wool made in the country
is made using copper slag?
ANSWER (Mr. Fowler): I said that approximately 70 percent is made using
steel mill slag and that the remainder is made using lead smelter
slagi copper smelter slag, iron smelter slag and natural rock.
QUESTION (Mr. Dickinson): Okay, but in essence some of it is made using
either lead or copper melting slag?
ANSWER (Mr. Fowler): That is correct.
QUESTION (Mr. Dickinson): Since arsenic occurs naturally in nature with those
materials did you do any sampling in the areas where that kind
of slag was being used to see what kind of exposure was being
given perhaps to the workers in the way of arsenic as opposed to
particulates? If we are looking at what the problems are in using
substitute materials for asbestos this might be something that we
ought to be considering.
ANSWER (Mr. Fowler): I did not look particularly at arsenic. We did
look at lead exposures. We found one single exposure to lead that
was above the then current OSHA standard. That was in a single
individual who was using personal respiratory protection as well.
So that his actual exposure would have been substantially less than
that measured. Other than that we did not find excessive exposures
to lead.
418
-------
MORTALITY PATTERNS OF ROCK AND SLAG
MINERAL WOOL PRODUCTION WORKERS
EPIDEMIOLOGIC AND ENVIRONMENTAL STUDY
by
Cynthia F. Robinson, M.S.*
Gregory 0. Ness, M.P.H.
Richard J. Waxweiler, Ph.D.
Industry-wide Studies Branch
Division of Surveillance, Hazard Evaluations and Field Studies
National Institute for Occupational Safety and Health
Center for Disease Control
Public Health Service
U.S. Department of Health, Education and Welfare
Cincinnati, Ohio
and
John M. Dement, Ph.D.
Division of Respiratory Disease Studies
Appalachian Laboratory for Occupational Safety and Health
Morgantown, West Virginia 26505
ABSTRACT
An epidemiolbgic and environmental study of rock and slag mineral wool produc-
tion workers was undertaken at a plant which has been in operation since the
early 1900's. Size characteristics of fibers produced by each process at the
plant and industrial hygiene survey data were used to evaluate current and past
exposures. These data suggest that the average historical airborne fiber con-
centration probably did not exceed 2.5 fibers/cc before 1935 and 1.0 fiber/cc
after 1935. A retrospective cohort mortality study was designed to assess
mortality patterns. Detailed occupational histories were compiled on all plant
employees. All jobs in the plant were assigned to one of eight potential expo-
sure categories to assess the extent of severity of mineral wool exposure and
the effect of other significant exposures on employee mortality. Findings
included an increase in the number of deaths due to digestive system cancer
and nonmalignant respiratory disease among workers who had greater than 30 years
exposure to mineral wool or who had survived 30 years since their first expo-
sure to mineral wool. These findings corroborate those of the Thermal Insula-
tion Manufacturers' mortality study of men employed in four mineral wool plants
(Enterline'and Marsh. 1979).
Presented by Cynthia F. Robinson, M.S. Paper is being prepared for publi-
cation elsewhere.
419
-------
DISCUSSION ON ROCK AND SLAG MINERAL WOOL
QUESTION (Mr. Shaines): Did you say that nothing in the data showed a signifi-
cantly greater death rate from the slag workers versus the county
workers?
ANSWER (Ms. Robinson): There was no statistically significant excess of
deaths.
QUESTION (Mr. Shaines): That is right. From that you conclude that there was
an increase in deaths?
ANSWER (Ms. Robinson): There was an increase of observed deaths over what
was expected.
QUESTION (Mr. Shaines): If it is not significant then it is- not an increase.
That is the meaning of the word.
ANSWER (Ms. Robinson): There were more deaths than what was expected.
REMARK (Mr. Shaines): Not significant.
REMARK (Mr. Wright): It was an increase but it was not statistically signi-
ficant. I think that is the way to say it.
REMARK (Mr. Shaines): That is right.
REMARK (Mr. Wright): That does not mean it is not an increase.
REMARK (Mr. Shaines): I will go through the words again. The probability
was that there was not an increase. That is what the word significant
means.
REMARK (Mr. Wright): It means the increase was not significant at the 0..05
level. That does not mean the probability was that there was no
increase whatsoever. All it means is the chances are less than 1
out of 20. r
REMARK (Mr. Shaines): That is right. The odds are 20 to 1 that there was
not an increase.
REMARK (Mr. Wright): No, just the opposite. In the 5 percent level the
odds are 20 to 1 that there is not an increase if it is not signifi-
cant. That is what the odds are.
REMARK (Dr. Bernstein): I would assume that your Null hypothesis is that
there is probably no increase. If that is the case, there is a 20 to
1 probability that your Null hypothesis is not true; therefore it is
a 20 to 1 probability that there is an increase.
REMARK (Ms. Robinson): If I can restate it again. I would say the odds are
that this - increase could have been seen by chance alone, however,
420
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there were more deaths occurring than was expected on the basis of
our comparison population.
REMARK (Unidentified): There were increases in several categories of cancer
and in almost all of these cases there was a latency period effect
present at 30 years. I think if you took the information on increases
in about three different types of cancer, essentially all of them
occurring at 30 years, and combined them by nonparametric techniques,
you would have no problem showing significance.
REMARK (Mr. Wright): I am fronTthe Steelworkers Union.
Just a quick comment about statistical significance. Two things would
be useful in these types of reports: first is the 95 percent confi-
dence interval around the results, and second is that even though it
is useful to say this finding was or was not significant at the 0.05
level, it might be interesting to know at what level it was
significant.
I would suspect for some of these numbers we are talking about maybe
the 0.1 or 0.2 level? Now no scientist in his or her right mind would
say that means those results are statistically significant, but they
might have meaning to a worker. For example, if a work place has a
result that is significant at the 0.1 level, the professional might
say that is not a statistically significant result and tests have not
proven that this stuff causes cancer or fibrotic lung disease. But
a worker looking at that result, if he or she understood the statistic,
might conclude quite correctly that the chances are nine to one that
there is a problem. That is what it means to say it is significant
at the 0.1 level, nine to one that there is a problem. It is not
enough to publish in a scientific paper how we have proven a problem
exists but it sure is enough to worry me. That is what those results
mean to me.
QUESTION (Mr. Castleman): I gather from what you said that a
asbestos was used, at least in that plant, and there
about the previous job histories of the workers. If
pathological material or autopsy records or possibly
more recent from someone in this group who had died,
the state of the tissues and learn a little bit more
going on there. ,
small amount of
was a question
you could get
something even
you could see
about what was
ANSWER (Ms. Robinson): Yes, that is a good suggestion. Unfortunately, there
are very few individuals involved in the study and the rate of obtain-
ing that kind of information and also tissue samples, which would be
needed., is very, very low. It has been less than 50 percent in our
previous attempts. However, I think we are attempting to do that.
QUESTION (Mr. Castlemen): What about obtaining chest x-rays from the individ-
uals who are in bad shape from nonmallgnant respiratory disease?
421
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ANSWER (Ms. Robinson): I do not know about that.
REMARK (Dr. Konzen): I am from TIMA.
I think epidemiology is a very strong tool. We use it a great deal,
as I pointed out in my talk. I think it is extremely Important to
remember that we are talking about one plant with a population of
about 500 people that is being studied.
As Ms. Robinson mentioned, the Thermal Insulation Manufacturers Asso-
ciation is carrying out a study that encompasses not only mineral wool
workers but fibrous glass workers. The first part of the study
reported little evidence of disease from a malignant or a nonmalignant
standpoint. This was a preliminary report and a further report, which
is expected the latter part of this year, will look at many more of
these mineral wool workers.
The other thing that is important to to keep in mind is the study that
I mentioned this afternoon. It was a larger study on fibrous glass
workers. In the study we found no excess of either malignant or non-
malignant disease in any category and the overall disease rate was
quite low. This study will be made available to the regulatory agencies
for review.
I think before we get excited about one plant we should use epidemi-
ology where it is strongest and that is in the largest population that
we can involve.
REMARK (Ms. Robinson): I would like to respond to the previous person who
asked a question because he did imply that the use of asbestos at this
plant was considerable. In fact, that was not the case as we under-
stand it.
REMARK (Mr. Cooper): I am from Berkeley.
I, having been involved in a number of epidemiclogic studies myself,
appreciate Ms. Robinson's dilemma and I think the final conclusions
that she came to were reasonable conclusions to arrive at from this
material. There are other things to consider and the question of
statistical significance and ideologic significance and social sig-
nificance are interrelated but different questions, and it would be
improper to say there was a nine to one chance of someone getting a
digestive cancer, even a nine to one chance of there being a problem.
The difficulty here is you have a relatively small increased risk
and a relatively small population and that combination leads to data
that are very difficult to use to establish statistical significance.
I think it would be wrong to combine into one analysis the respiratory
tract cancers and the nonmalignant respiratory diseases with the
digestive cancers to show significance. The respiratory disease
cancers are quite a different problem. The interfering effects of
422
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smoking are so overriding in many industrial populations that they
cannot easily explain the difference you see in this population.
Secondly, they tend to coincide with the duration of employment so
you tend to get a spurious appearance of latency. I think this would
be incorrect.
I think the nonsignificant and rather small increase in digestive
tract cancer is something that I would regard with concern and some-
thing that needs further study. We are dealing with raw materials
that may potentially contain carcinogens. So, I feel the very guarded
conclusions that came from NIOSH were warrented conclusions.
REMARK (Ms. Robinson): It is hoped that futher follow-up of this study as
well as the others will produce more definitive conclusions.
REMARK (Mr. Scheckler): I am from TIMA.
I had an opportunity to review some of the records at that particular
plant. The one thing I found missing in your presentation was the
fact that there was an interchange of employees between the studied
plant and an adjacent plant 40 miles away owned by the same company.
That interchange of personnel back and forth did not show on the
records. Now I cannot tell you the materials manufactured at the
other plant. That would have to be reinvestigated. But this exchange
of people did take place quite often.
423
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INDUSTRIAL HYGIENE AND TOXICOLOGY ASPECTS OF
3M NEXTEL® 312 CERAMIC FIBERS
by
Mr. Robert S. Larsen and Mr. William McCormick*
3M Company
St. Paul, Minnesota
ABSTRACT
NEXTEL® 312 Ceramic Fibers are continuous filaments. Individual filaments
are comprised of metal oxides, are transparent, smooth and round, and are
microcrystalline in structure. The nominal diameter of the continuous ^
filaments is 11 microns. The primary health effect associated with NEXTEL
312 Ceramic Fibers is skin irritation. However, tolerance to the irritation
develops after several days of handling. Irritation studies and worker
exposure data are discussed. Airborne fiber concentrations measured in a
3M manufacturing facility and in a customer facility involving several
operations have been shown to be extremely low (maximum of 0.0005 fibers/cc
air). The length of the airborne fiber is quite variable (20-6,200 microns)
and the diameter is generally' greater than 10 microns. Airborne fibers are
thus classified as being essentially nonrespirable.
Toxicity studies are currently under way to evaluate the fibrogenic potential
of NEXTEL® fiber. Some comparisons to asbestos and fiberglass are made. The
inhalation hazard associated with NEXTEL® 312 Ceramic Fibers is judged to be
minimal.
NEXTEL 312, manufactured by 3M is a ceramic textile fiber. The 11 micron
diameter continuous filaments have a variety of properties including low
thermal conductivity, high temperature resistance, and electrical non-
conductivity. Products made from this fiber include fabrics, tapes, sleeving,
and cordage (Figure 0).
The first portion of this presentation will be an introduction to the
fibers and their toxicity. Secondly, the results of industrial hygiene studies
will be discussed.
* Presented by Mr. Robert S. Larsen.
425
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Figure "0" Products made with NEXTEL 312
Ceramic Fibers
a. Fabrics
b. Tapes
c. Sleeving
d. Cordage
426
-------
NEXTEL FIBER AND TOXICITY
Figure 1
The uniform roundness of the fiber is apparent in this scanning electron
microscope photograph showing a cross section of three fractured filaments
at 6000 X magnification.
Figure 2
As you can see in this figure, the round fibers have a uniform smoothness.
Figure 3
In the next figure, a 100 X magnification photograph shows the uniform,
transparent quality of the filaments.
The typical NEXTEL® 312 ceramic fiber is comprised of three inorganic
Figure 4
The
oxides in the following percentages:
:ent
(Figure 4)
Aluminum oxide
Boron oxide
Silicon dioxide
62 ^percent
14 percent
24 percent
In processing, the fiber attains a microcrystalline structure.
Figure 5
As you can see, the micrograin crystals of the NEXTEL fiber shown in
the top photomicrograph are approximately 0.01 to 0.02 microns in length.
This can be compared to other ceramic materials having much larger "fine-grain"
ceramic crystals (seen in the middle photograph) and an amorphous form of
noncrystalline ceramic structure seen in the bottom photograph.
®
NEXTEL ceramic fibers are manufactured to be an 11 micron diameter con-
tinuous filament. 3M began selling ceramic fibers commercially in 1977. As
a result, there has been insufficient time to develop a history of any possible
chronic human health effects. Since the fibers are of such large diameter,
the inhalation hazard associated with their manufacture and use is believed to
be quite low. Industrial hygiene surveys conducted in both manufacturing and
user facilities have confirmed this and will be expanded upon later.
The fiber has been assessed for its skin and eye irritation potential in
the rabbit.
Table 1
This table shows the results of the primary skin irritation study
conducted on the fiber. The study conducted was a conventional Draize primary
skin irritation study1 using the Federal Hazardous Substances Act protocol
427
-------
Figure 1 Roundness of the fiber (6000 X)
428
-------
Figure 2 Smoothness of the fiber surface
429
-------
Figure 3 Transparent Quality of the Filaments
431
-------
Figure 5 Contrast between three ceramic structures
"Micrograin" - NEXTELR 312
"Fine Grain" - Aluminum Oxide
"Amorphous" - Fibrous Glass
433
-------
TABLE 1. NEXTEL 312 CERAMIC FIBER PRIMARY SKIN IRRITATION
Erythema and
Eschar Formation
Intact Skin
Intact Skin
Abraded Skin
Abraded Skin
Edema Formation
Intact Skin
Intact Skin
Abraded Skin
Abraded Skin
Primary Irritation
Reading
(hours)
24
72
24
72
24
72
24
72
Score: 1
Rabbit number
1
1
1
1
1
0
0
0
0
.67 - 4
2 3
1 0
0 0
1 0
0 0
Subtotal
0 0
0 0
0 0
0 0
Subtotal
Total
= 0.42
4
0
0
1
0
0
0
0
0
5
1
0
1
1
0
0
0
0
6
0
0
0
0
0
0
0
0
Average
0.50
0.17
0.67
0.33
1.67
0.00
O.OU
0.00
0.00
0.00
1.67
434
-------
and scoring method.2 A 0.5 gram sample of the test material was placed
on intact and abraded skin test sites on 6 albino rabbits for a period of 24
hours. After removal of the occluded patch, the sites were scored for
erythema and edema formation. At 3 of 6 intact sites and 4 of 6 abraded
sites, slight reddening was observed at the 24 hour reading. At intact sites
the score was 0.5. At the abraded sites the score was 0.67. By the 72 hour
reading the irritation was reduced to 0.17 at the intact sites and 0.33 at
the abraded sites. The total primary skin irritation score was 0.42. This
classifies the fiber as minimally irritating dermally.
These data are confirmed in plant experience. People initially working
with ceramic fibers tend to experience a low grade irritation response. The
response fades within several days of working with the fiber. The experience
is similar to the fiberglass skin reactions noted by several researchers
(Sulzberger, et al, and Erwin).3*1* The eye irritation results showed that
the ceramic fiber failed to elicit any signs of irritation in any animal on
study. Again, plant experience indicates eye irritation problems in persons
handling ceramic fibers are quite rare.
The acute skin and eye data on NEXTEL fibers indicate a relatively
low hazard in the handling and processing of the product. However, of primary
concern is the possible chronic effects of inhalation exposure to the fiber.
As I mentioned earlier, NEXTEL ceramic fibers are, in the realm of fiber
dimensions, quite large. Their diameters are in the 11 micron range and the
lengths are essentially continuous. Short fibers are created as the result
of breakage of the continuous filament. Breakage is of low enough incidence
in manufacture and usage to preclude a significant build up of airborne fibers.
Many of the fibers that are created are large enough to settle out of the air
rather than remain suspended. Therefore, they are unavailable for inhalation.
Additionally, longitudinal fracturing, a process which commonly occurs with
asbestos fibers, has not been encountered with NEXTEL ceramic fibers.
Because of the above considerations, 3M has not conducted any fiber
inhalation studies, acute or chronic. Fibers of large diameter and length
are considered nonrespirable. If inhaled they would be expected to be inter-
cepted in the nasopharyngeal region of the respiratory tract and eliminated
through normal clearance mechanisms (Timbrell, Harris and Fraser).5'6 Research
conducted by Stanton, Timbrell, Wagner,7»s»8 and others indicate there is a
relationship between fiber geometry and an adverse biological response. It
is believed that for a given fiber diameter the longer the fiber the greater
the likelihood of adverse biological response. However, the fiber diameter
must be less than 5 microns.
Although current information suggests exposure to NEXTEL® fibers is
extremely low, 3M is beginning an intratracheal insufflation study to deter-
mine the fibrogenic potential of the fiber.
Additionally, and more importantly, the industrial hygiene surveys
conducted by 3M indicate air concentrations of ceramic fibers to be very low,
thus diminishing the concern of inhalation exposure hazard.
435
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INDUSTRIAL HYGIENE ASPECTS
Table 2
Industrial hygiene studies have been conducted at a 3M production
facility and customer facility in order to determine the concentrations
(fibers/cc) or airborne NEXTEL 312 ceramic fibers to which employees are
exposed in addition to the physical characteristics (length, diameter) of
the fiber. I will discuss sampling procedures, analytical methods, results
of the studies and a comparison of the results with existing OSHA standards
and NIOSH proposals for other fiber types.
Table 3 - Sampling
Personal and general area air samples were collected on open-faced type
AA Millipore filters. Sampling times were up to 60 minutes in duration and
dependent upon the particular operation being monitored.
Table 4 - Analysis
The whole filter was cbunted using an Ortholux microscope. The ceramic
fibers are relatively easy to identify on the filter. However, it is possible
that other airborne fibers may have been counted in addition to the ceramic
fibers.
Table 5 - Results
An industrial hygiene survey was conducted in a textile operation using
the fibers. Airborne ceramic fiber concentrations found in the customer
facility are judged to be very low for the various processes monitored. The
mean airborne concentration for all processes monitored was 0.00004 fibers/cc
of air. The airborne fibers may be characterized as being quite long with a
correspondingly large diameter. The mean length was 261 microns and the mean
diameter 10 microns. The airborne fibers in th§ textile plant may be classi-
fied as being nonrespirable. The inhalation for 3M customers handling the
fibers is judged to be minimal.
Table 6
Much the same results were found in 3M's ceramic fiber production
facility. However, the length and diameter of the airborne fibers in 3M's
production facility are quite a bit larger than the fibers found in the
customer facility. This is due primarily to the inherent nature of the
manufacturing process which results in the generation of larger airborne
ceramic fibers. The mean airborne concentration was found to be 0.0001 fibers/
cc of air. The mean airborne fiber length was 986 microns and mean diameter
25.8 microns.
Table 7 - Comparison of Results with Standards and Proposals
None of the airborne ceramic fibers found in these studies would be
considered countable under the existing OSHA asbestos standard and proposed
436
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TABLE 2. INDUSTRIAL HYGIENE STUDIES ASSOCIATED
WITH AIRBORNE 3M NEXTEL® 312 CERAMIC
FIBERS
I. Sampling
II. Analysis
III. Results
A. Customer Facility
B. 3M Production Facility
IV. Comparison of Results with OSHA Standards and
1JIOSH Proposal for Other Types of Fibers
TABLE 3. SAMPLING
1. AA Millipore Filter (open-faced)
2. Flowrate -2.5 LPM
Duration - up to 60 minutes
3. Personal and area samples
TABLE 4. ANALYSIS
1. Ortholux Microscope
A. Count whole filter
B. Use mechanical stage
C. Use micrometer eyepiece
2. Ceramic fibers are relatively easy to
identify but may also be counting
other airborne fibers on the filter.
437
-------
TABLE 5. RESULTS - CUSTOMER FACILITY PERSONAL SAMPLES
10
00
Concentration
Operations (No. fibers/cc air)
1 . Serving 0 . 00004
2. Serving 0.00001
3. Core Winding 0.000007
4. Weaving 0.00005
Mean 0.00004
Fiber
on filter Length
6 120
192
216
264
300
300
2 108
792
1 120
8 151
180
215
229
264
300
324
360
4.25 261
sizes (y)
Diameter
13.5
8.1
8.1
8.1
10.8
10.8
10.8
10.8
8.1
10.8
10.8
10.8
10.8
8.1
8.1
9.5
10.8
10
-------
TABLE 6. RESULTS - 3M PRODUCTION FACILITY
Range of
fiber sizes (y)
Sample description
Area samples taken in
fired fiber locations
Mean
i>uuueu.L.Lci(..Luu range
(No. fibers /cc air)
0-0.0005
0.0001
fumge uo. «u .
fibers on filter
0-14
4.6
Length
20-6200
986
Diameter
9.3-37
25.8
Co
vo
TABLE 7. OSHA STANDARD AND NIOSH PROPOSAL
Fiber size
Dtanaara or
proposal
OSHA - Asbestos
NIOSH - Fiberglass
NEXTEL Ceramic Fibers -
3M Mean
Customer Mean
No. fibers/cc air
2 (TWA)
3 (TWA)
0.0001
0.00004
Length
>5
I10
986
261
Diameter
*
£3.5
25.8
10
An asbestos fiber is defined as a particulate form,of asbestos,
longer than 5y, with a length to diameter ratio of at least
3 to 1 and a maximum of 5y.
-------
NIOSH Fiberglass Recommended Standard.9 Even if the fibers were considered
countable, the airborne concentrations which were detected are well within
the concentration limits set forth in the Asbestos Standards and Fiberglass
proposal.
In conclusion NEXTEL 312 ceramic fibers are continuous filament large
diameter fibers that present a low inhalation hazard in manufacture and
processing. They represent a relatively safe alternative to asbestos in
the thermal protection fabric area.
BIBLIOGRAPHY
1. Draize, J. H., Woodard, G. and Calvery, H. 0. Methods for the Study of
Irritation and Toxicity of Substances Applied Topically to the Skin and
Mucous Membranes. J. Pharmacol. Exp. Ther. 82:377-390, 1944.
2. Chapter II, Title 16 Code of Federal Regulations §1500.41 Methods of
Testing Primary Irritant Substances and §1500.42 Test for Eye Irritants.
3. Sulzberger, M. B., Baer, R. L., Lowenberg, C. and Menzel, H.: The
Effects of Fiberglass on Animal and Human Skin - Experimental Investi-
gation. Ind. Med. 11:482-84, 1942.
4. Erwin, J. R.: Fiberglass Plastics. Ind. Med.: 439-41, 1947.
5. Timbrell, V., The Inhalation of Fibrous Dusts. Section V - Human
Exposure to Asbestos: Dust Controls and Standards. Ann. NY Acad.
Sci.: 132:255-73, 1965.
6. Harris, R. L. and Fraser, D. A., A Model for Depositon of Fibers in the
Human Respiratory System. AIHA Journal: 37:73-89, 1976.
7. Stanton, M. F., Layard, M., Tegiris, A., Miller, E., May M. and
Kent, E.: Carcinogenicity of Fibrous Glass: Pleural Response in the
Rat in Relation to Fiber Dimension. J. Natl. Cancer Inst.: 58 Mo. 3:
587-603, 1977.
8. Wagner, J. C., Berry, G., Skidmore, J. W.: Studies of the Carcinogenic
Effects of Fiberglass of Different Diameters Following Intrapleural
Inoculations in Experimental Animals. Occupational Exposure to Fibrous
Glass-Proceedings of a Symposium, HEW Publication No. (NIOSH) 76-151
193-197. Washington, DC, U.S. Department of Health, Education, and
Welfare, 1976.
9. Criteria for a Recommended Standard, Occupational Exposure to Fibrous
Glass. DHEW (NIOSH) 77-152. Washington, DC, U.S. Department of Health,
Education and Welfare, 1977.
440
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DISCUSSION ON CERAMIC FIBERS
QUESTION (Dr. Cooper): If there is no question on this particular paper
I would like to clarify my comments on the previous paper* if
this is in order.
ANSWER (Chairman Rowe): That is fine.
REMARK (Dr. Cooper): There are some individuals here who seem to have
the impression that I said that I felt the NIOSH study showed
that mineral wool caused an increase of digestive cancer. This
was not what I intended to convey at all. The point I meant to
make was that I agreed with the conclusions of Ms. Robinson
that the study was inconclusive and that this was an area that
certainly deserved further study.
441
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TOXICOLOGY OF ARAMID FIBERS
by
C. F. Reinhardt, M. D.
Haskell Laboratory for Toxicology and Industrial Medicine
E. I. du Pont de Nemours and Company
Wilmington, Delaware 19898
ABSTRACT
® A
Du Font's two high performance aramid fibers, Kevlar and Nomex , are function-
ally qualified and cost-effective as asbestos replacements in many industrial
applications. Both fibers are based on aromatic polyamides, which confer excel-
lent high temperature stability and, with Kevlar , outstanding strength, stiff-
ness and frictional properties over a wide temperature range. Several trade
programs are under way to replace asbestos in friction products, gasketing,
plastic reinforcement, thermal Insulation and protective clothing.
A ®
Neither Nomex nor Kevlar fibers produce allergenic reactions on skin contact.
Initial inhalation and/or intratracheal insufflation studies of fibers of Nomex
and polymeric dust of Kevlar® in rats showed that both materials produced only
minimal tissue reaction (nature of reaction varied with particle size and shape)
in the lungs with no collagen formation. These observations appear to meet the
criteria of a biologically inert dust, namely: (a) absence of collagen forma-
tion; (b) potential reversibility of the lesions; and (c) maintenance of normal
architecture of the air spaces.
Results of these preliminary studies indicate that the use of aramid fibers to
replace asbestos poses no significant health hazard to persons processing ara-
mids or to the user of the final product. More extensive toxicological studies
are planned'to confirm these results.
INTRODUCTION
Du Font's two aramid fibers, Nomex and Kevlar , are rapidly gaining accep-
tance as commercially viable replacements for asbestos in a number of applica-
tions such as insulation, flame barriers, thermal protective clothing, and
particularly, friction products.
Key to the functional acceptability of Nomex and Kevlar is their chemical
structure. Both are based on aromatic polyamides .and differ only in the sub-
stitution position on the aromatic rings. These fibers are inherently flame
443
-------
resistant and do not melt. In fact, neither will sustain combustion in a nor-
mal atmosphere when the ignition source is removed. Thermal and oxidative
stabilities are also outstanding, so that each can withstand long-term in-use
exposure at very high temperatures for organic fibers.
® ®
Nomex and Kevlar fibers have been sold commercially for about 15 and 8
years respectively. To date, industry has consumed millions of pounds of each
material with no known health hazards from the fibers either in manufacture or
use.
I will turn now to a description of the procedures and results of our
toxicological testing of Nomex®and Kevlar®.
PROCEDURES AND RESULTS
Human contact with these fibers is most likely to be by the dermal route
along with potential respiratory exposure, so we have concentrated our efforts
on these exposure routes. Both Nomex® and Kevlar have been studied to evalu-
ate skin irritancy and skin sensitization potential in animals and man. These
studies involved primarily human volunteer panels in which from 100 to 200 in-
dividuals per study were patch tested. They showed no potential for skin sen-
sitization and only minimal chance for skin irritation to develop following der-
mal contact with fabrics of either Nomex® or Kevlar® . Because these fibers,
especially Kevlar , are stiff, potential exists for causing abrasive skin
irritation under restrictive contact.
To evaluate the potential problems that might be associated with respira-
tory exposure to Nomex® , the long-term lung response to dust generated by
shredding and grinding a paper of Nomex aramid was studied. Two and one—half
milligrams of the material, suspended in physiological saline solution, was
instilled into the trachea of rats. The test material in the lung appeared
as acicular, oblong, or rod-shaped particles varying in size from 2-100u in
length and 2-30u in diameter. Tissue response was measured by evaluating the
respiratory tract histopathologically. Groups of rats were examined 2 and 7
days, 3 and 6 months, and 1 and 2 years following treatment.
No signs of an adverse response to the test substance were seen - these
included observations for clinical signs, growth as measured by body weight
data, and mortality patterns. At each of the sacrifice intervals, the test
material was observed microscopically in the lung tissue. However, the non-
specific tissue response was characteristic of that experienced generally with
foreign particles in the lung; that is, an initial transitory acute inflamma-
tory response followed by foreign body granuloma formation. The later response
was provoked by the larger, non-respirable sized dust particles in the range of
30 X lOOu. The smaller, respirable sized particles, <10u, produced only a
negligible dust cell reaction similar to that seen with nuisance particulates.
During the post-exposure recovery period, most of the dust laden macrophages
were eliminated from the lung within three months.
These mild tissue reactions became less obvious as the post-exposure time
increased and the exposed lungs returned to essentially normal architecture
without formation.of collagenized fibrosis two years after exposure. This ex-
444
-------
pertinent In rats irit rat radically insufflated with fibrous dust of Nomex did
not show any progressive pulmonary fibrosis, collagenization or clinical bron-
chopulmonary distress.
We next concentrated our efforts on Kevlar since it is a rather unique
fiber in that it has a greater tendency than most fibers to fracture along the
fiber axis. In some textile processing operations it has a propensity to form
some small fibrous particles. That characteristic, along with Du Font's inter-
est in very short, highly fibrillated pulp forms as an asbestos replacement,
has caused us to center our concern on these small particles. We started with
dust converted from raw polymer, rather than dust converted from fiber, since
we could not isolate enough fiber dust from textile processing operations for
our tests.
The polymer dust tested contained a low, but undetermined proportion of
fibrous particles considered to be in the respirable range, <1.5u in diameter
and between 5 and 60u in length. Larger, non-respirable particles ranged up
to 150u in diameter. Particle shapes were variable. Chemically, this material
is identical to fiber particulates. In our first study, the acute inhalation
toxicity potential was measured by generating the highest dust concentration
possible and by exposing rats to this atmosphere for 4 hours. Concentrations
in the exposure chamber were analyzed gravimetrically and averaged 150 mg/m3.
Only minor signs of a response, such as decreased activity, were seen during
the exposure period. No signs of a response were seen post-exposure. The acute
lethal concentration in rats is thus in excess of 150 mg/m3. However, as in-
dicated above, only a small percentage of the dust was of respirable size.
Since we were concerned with not only the effects of a single massive ex-
posure but also with potential cumulative effects following a series of expo-
sures, a subacute inhalation study of the Kevlar® polymer dust followed. In
this experiment, rats were exposed to 130 mg polymer dust per m3 air for 4 hours
per day, 5 days per week for each of 2 successive weeks. Observations of the
rats for clinical response to the dust were made daily. A reference group of
control rats exposed to houseline air only was run concurrently. Immediately
following the last exposure, half of each group, test and control, was sacri-
ficed" and each rat was given a complete gross pathological examination includ-
ing weights of the lungs and other major organs. Microscopic examinations of
21 tissues/organs were conducted. The remaining rats were sacrificed and
examined similarly following a 14-day recovery period.
During the exposures, test rats were slightly less active and gained some-
what less weight than did the controls. This was not seen during the recovery
period. Gross pathological examination and organ weight data revealed no treat-
ment-related differences.
Microscopically, rats examined after the 10th exposure showed numerous
macrophages throughout the lung tissue. At the end of the recovery period,
these macrophages decreased in number and tended to form discrete clusters in-
dicating a typical non-specific response to foreign particles in the lung. All
other tissues and organs examined either immediately following exposure or after
the recovery period were free of treatment-related changes.
445
-------
Repeated exposure of rats to 130 mg of polymer dust/m3 produced only mild
clinical symptoms during, but not after, exposure. A slight change was produced
in the lung, manifested by phagocytosis of the test material. This typical dust-
call reaction was also observed following the 14-day recovery period.
To evaluate the tissue response on a long-term basis, the next study in-
volved intratracheal instillation of 25 mg of Kevlar® polymer dust in physio-
logical saline solution into rats. A group of control rats treated with saline
alone was included. Rats were then held without further treatment and were sac-
rificed at 2, 7, and 49 days and 3, 6, 12 and 21 months after treatment.
At each sacrifice, a complete gross pathologic examination including weights
of the major organs was conducted. Histopathologic examination of the respira-
tory tract was also conducted.
Over the 21-month test period, mortality rates, clinical observations, and
gross autopsy results were similar for test and control groups.
Following instillation, particles could be detected in lung tissue, the
large particles, approximately 100-150u in diameter, mainly in terminal bron-
chioles, smaller-sized particles, approximately 5u in size, in alveolar ducts.
The initial, non-specific inflammatory response subsided within 1 week and
foreign body granulomas containing the larger non-respirable dust particles were
seen in later sacrifices. Negligible amounts of collagen were present around
the dust-laden large granulomas. All tissue responses to the dust particles
decreased with increasing time post-treatment.
From this experiment, we conclude that the intratracheal instillation of
respirable and non-respirable-sized polymer dust particles of Kevlar® produced
only a non-specific dust cell reaction similar to that seen with inert dusts.
The material is considered non-fibrogenic and only mildly irritating since the
pulmonary lesions showed marked reversibility, no collagen formation associated
with the respirable-sized dust particles, and only the large, non-respirable
dust particles were able to produce foreign body granulomas.
We are currently engaged in a program to evaluate fibrous particles de-
rived from ground Kevlar® aramid fiber (pulp), for which we expect to find wide
use as an asbestos replacement. This includes a subacute inhalation study with
extended recovery times and insufflation with the dust of fibrous particles.
The need for other work, including the possibility of a lifetime inhalation
study, will be evaluated as the results of the currently planned studies become
available.
COMMENTARY
These toxicological test results give us confidence that neither Nomex®
nor Kevlar* poses a significant health hazard to our workers, to those who
process the fiber into asbestos replacement products, or to the end users of
those products. This position is supported by the safe use of millions of
pounds of aramid fibers in a range of other end uses over many years and good
medical surveillance of our employees who have handled them. While the test
conditions utilized do not simulate directly real-life exposures to these pro-
446
-------
ducts, we believe that, if anything, the tests exaggerate use conditions. Our
toxicological testing program is continuing in order to document our hazard
assessment and to provide added support as the range of end uses increases.
447
-------
DISCUSSION ON ARAMID FIBERS
QUESTION (Mr. Spitzer): I am from the Consumer Product Safety Commission.
Three quick technical questions: (1) how many animals were in each
group that you used; (2) what about the spontaneous tumors in each
group; and (3) have you done any transmission electron microscopy, and
specifically looked at the type 1 to type 2 cell ratio in the lung
tissue?
ANSWER (Dr. Reinhardt): In response to the first question, there were approxi-
mately 40 animals in each group and 5 were sacrificed at each of the
intervals, holding the remaining ones until the end. Your last ques-
tion about the electron microscopy, that has not been done. And your
second question about tumor incidence will be answered by our path-
ologist who reads these slides, Dr. Lee.
ANSWER (Dr. Lee): Each period we sacrificed five rats. At the end of 21
months there were about five rats left. Therefore, it is almost
impossible to check the carcinogenicity with that small a number of
animals. So we cannot answer that question.
QUESTION (Dr. Lewinsohn): I am from Raybestos-Manhattan.
With regard to the question of carcinogenicity, I assume that you
will be conducting survival type experiments to determine whether
there is an incidence of carcinogenicity in these animals. And I
wonder have you considered the instillation of fiber into the pleural
cavity directly, in other words, the Stanton type experiment?
ANSWER (Dr. Reinhardt): As far as answering your first question, yes, def-
initely. In particularly the longer term type studies that we do,
the animals will be held for their lifetime to evaluate any carcin-
ogenic potential. In elaborating a bit on Dr. Lee's response, even
though the numbers of animals was relatively small at the end of the
study so that it would make it difficult to evaluate with great
assurance the absence of any carcinogenic potential, there was no
evidence that this was a problem based on the studies that we have
done up to this point. Right at the moment we do not have any plans
to carry out pleural instillation. We feel that the insufflation* studies
and the more physiological inhalation studies would be appropriate.
REMARK (Dr. Cooper): I am from Berkeley.
Several years ago, Pimental, Avila, and Villar, in Portugal, des-
cribed pulmonary reactions in a variety of industries where more or
less insoluble and durable dust was inhaled. I looked into this
briefly and it appeared that there was a pattern of exaggerated gran-
ulomatous response in a number of individuals, including individuals
who had worked with a number of the synthetic textile fibers. I have
not heard anything about this lately, but it is suggested with the
type of response that you see in your animals that an occasional
448
-------
Individual might have an exaggerated granulomatous response to
the deposition, inhalation or retention of some of these dusts*
which simulates a sarcoid-like reaction. I just wondered if there
have been any human experiences in the United States that would
suggest that occasionally individuals would have this. It is not
a fibrosis, it is not a pneumoconiosis, but it could create an
Impression that you are getting a pneumoconiosis when it really
is probably a highly individualized response. I wonder if you
would comment on this general topic.
ANSWER (Dr. Reinhardt) : I am also familiar with the Portugal study. To
the best of my knowledge I do not know of any actual studies
where there are autopsy findings correlating a response such as
you describe, this granulomatous response, with the exposure to
specific fibers. In the Portugal study, I think there were numerous
fibers in the lungs of these people, but their previous occupations
were not well documented. I appreciate your comment. I think that
It is something that perhaps needs to be pursued.
QUESTION (Chairman Rowe): Did you examine any other tissues to see if there
were particles in those tissues? And this is a general question:
What is the relationship between a granulomatous response and, say,
the development of fibrosis, if any?
ANSWER (Dr. Reinhardt): We did not examine the other tissues specifically
to see if there were fibers that had been translocated. I would
like to refer that second question back to Dr. Lee, our pathologist.
ANSWER (Dr. Lee): We checked lymph nodes and after 1 week the small
particulates were transferred to lymph nodes without any
significant inflammatory reaction. Your second question regarding
pulmonary fibrosis; it was not striking to observe the more
fibrogenic reaction in the large granuloma. So we think these
are nonfibrogenic fibers.
449
-------
ENVIRONMENTAL EXPOSURE CONSIDERATIONS DUE TO THE RELEASE
OF GRAPHITE FIBERS DURING AIRCRAFT FIRES
by
Dr. Benjamin Sussholz
TRW Defense and Space Systems Group
Redondo Beach, California 90278
ABSTRACT
Estimates are developed of the environmental criteria associated with micron
size carbon fibers released from burning graphite composites during aircraft
fires. Empirical fiber distributions were determined from test results of
exposure of graphite composite structural elements to large pool fires. Fre-
quency and dimensions of the micron carbon fibers were characterized. Fibril-
lated particles were observed which constituted the predominant source of
the micron fiber data. The fibrillation phenomena were attributed to fiber
oxidation effects caused by the fire environment. Estimates were established
of micron carbon fiber concentration and exposure levels for an extreme case
of an aircraft accident, and comparisons were made with OSHA criteria for
asbestos exposure.
Estimates have been developed of the dimensions and frequency of occur-
rence of small-diameter carbon fibers released from burning graphite compos-
ites during aircraft fires as a frame of reference for comparison with envir-
onmental exposure criteria established for known fiber hazards.
Development of the micron fiber criteria was based principally on data
reduction and analysis of sticky paper records obtained during large pool
fire tests of spoiler and cockpit structural samples conducted at the Naval
Weapons Center, China Lake, in May 1978.1 The sticky paper instrumentation
consisted of sheets of adhesive coated paper of approximately 20 cm x 25 cm
in dimensions located on wooden platforms of about 0.6 m height above ground.
Station locations ranged about 75 m to 115 m from the test samples covering
an arc of about 100 degrees. Data reduction consisted of determining carbon
fiber dimensions by means of optical microscopy.
An effort was made to determine appropriate diameter and length bounds
for carbon fibers that may be potentially respirable by humans and of interest
toward establishing fiber hazard criteria. There appears to be evidence that
durable fibers of similar dimensional characteristics constitute health
hazards simply because of physical properties rather than chemical nature.
451
-------
Extensive studies have been performed regarding health hazards associated
with asbestos and glass fibers with very limited research relative to carbon
fibers.
Due to the lack of specifically developed guidelines regarding carbon
fiber hazards it has been generally recommended that the existing framework of
information on asbestos and glass fibers may be applied toward establishing
bounds on carbon fiber criteria. Based on a review of the state of the art3"7
the limiting carbon fibers dimensions of interest toward health hazards were
assumed as follows: (1) diameter less than 3 microns, (2) length less than
80 microns, and (3) length-to-diameter ratio of 3 or greater.
During the course of data reduction of the NWC sticky paper records par-
ticles were observed which manifested a splitting or fibrillation process in
that single fibers appeared to be segmented longitudinally along the axis of
the fiber into individual fiber elements or essentially fibrils. Examples of
particles of this nature are shown in Figure 1. In some cases the particles
are characterized by substantial fragmentation of the slender fibers into
short segments. Representative fibrillated fibers with high micron particle
density are shown in Figure 2, with an enlarged view of a high density region
presented in Figure 3.
Evaluation of the NWC data indicated that the fibrillated particles con-
stituted the predominant source of micron size fibers of interest toward con-
sideration of potential health hazards. An effort was made to separate some
of the fibrillated particles from the adhesive on the records for detailed
examination by means of a scanning electron microscope. However, a difficulty
developed in preparation of the fiber sample for SEM photography in that com-
plete removal of the adhesive was not possible without a thin layer adhering
to the fiber surface. This layer was significantly greater than the depth of
focus of the SEM equipment, and therefore, the particle could not be observed.
Recommendation was made to NASA that Fetri dish instrumentation be incor-
porated in forthcoming pool fire tests of graphite composite structures at the
Dugway Proving Ground in order that free carbon fibers may be collected unen-
cumbered by the adhesive coating associated with sticky paper records. The
DPG tests were conducted during October-November 1979. Petri dish instrumen-
tation was distributed over an arc of about 120 degrees at a distance of
approximately 110 m from the test samples. A comparison of the NWC and DPG
test characteristics is presented in Table 1.
Analytical results for the length versus diameter distribution for NWC 11
is shown in Table 2, with a similar tabulation for NWC 13 given in Table 3.
For the case of NWC 11 a total of 191 micron fibers (D<3y, L<80y) were observed
with a corresponding frequency of occurrence of 38.4 percent. The number of
single fibers with lengths > 1 mm was 32, or 6.4 percent. The ratio of micron
fibers to single fibers with L > 1 mm was therefore 6.0. Relative to the NWC
13 data, 262 micron fibers were~measured with a frequency of 49.5 percent.
The number of single fibers with L > 1 mm was 30, or 5.7 percent. The ratio
of micron fibers to single fibers with L > 1 mm was 8.7.
452
-------
GAGE LOCATION SON, SOW
GAGE LOCATION SON, OE/W
Figure 1. Examples of Fibrillation Effect During NWC Spoiler Test 11
-------
NWC 11 140N, 60W
NWC 13- 180N, 40W
700 H
1400
Figure 2. Representative Fibrillated Fibers with High Micron Particle Density
-------
NWC 13- 180N, 40W
100 M
Figure 3. Enlarged View of High Micron Particle Density Region
-------
TABLE 1. TEST DATA SOURCES
00
Test Test Test
location designation sample
Naval WC "
Weapons
C6nter NWC 13
D-l
Dugway
Proving D-2
Ground
D-3
737 Spoilers
F-16 Cockpit
Various
structural
elements
Burn
Composite Composite Test duration
type mass (kg) configuration (min)
T300/5209 3.8 JP-5 pool fire 4
T300/5208 22.5 (12 m x 18 m) 6
T300/5208 46.2 JP-4 pool fire 20
T300/5208 45.5 (10.7 m diameter) 20
T300/5208 70.8 20
Test
instrumentation
Sticky paper
Sticky paper
Petri dish
Petri dish
Petri dish
-------
TABLE 2. SPOILER TEST NWC 1 I—LENGTH VS DIAMETER CORRELATION
Diameter
interval
(microns)
0-1
1-2
2-3
3-4
4-5
5-6
Ul
vo
6-7
7-8
>8
Total
Percent
Length interval
5- 10-
10 20
12 17
6 18
21
2 5
2 5
1
2
1
1
22 71
4.4 14.3
20-
40
8
33
22
5
3
1
3
1
15
91
18.3
40-
75
2
17
28
4
-
2
6
4
23
86
17.3
75-
150
4
8
23
11
9
6
6
3
5
75
15.1
150-
300
-
3
14
10
7
5
4
-
1
43
8.7
300-
600
-
1
7
10
6
5
9
4
4
46
9.3
(microns)
600-
1000
-
1
3
2
5
2
5
2
7
27
5.4
1000-
2000
-
-
2
5
3
4
4
2
2
22
4.4
2000- 4000-
4000 8000
-
-
1 1
2 1
4 1
•M 1—
1
1 1
9 4
1.8 0.8
8000-
16,000 Total
43
87
1 122
57
45
26
39
18
60
1 497
0.2 100
Percent
8.7
17.5
24.5
11.5
9.1
5.2
7.8
3.6
12.1
100.0
-------
TABLE 3. COCKPIT TEST NWC 13—LENGTH VS DIAMETER CORRELATION
Diameter
interval
(microns)
0-1
1-2
2-3
3-4
4-5
5-6
6-7
7-8
>8
Total
Percent
Length interval
5- 10-
10 20
14 16
11 30
7
1
-
-
_ _
- _
- _
25 54
4.7 10.2
20-
40
18
57
31
5
1
-
-
-
-
112
21.2
40-
75
6
36
27
9
3
-
-
2
1
84
15.9
75-
150
1
30
32
5
4
7
5
4
5
93
17.6
150-
300
-
11
14
14
7
2
3
4
8
63
11.9
300-
600
-
2
7
7
6
2
2
3
5
34
6.4
(microns)
600-
1000
-
2
4
5
1
1
2
1
6
22
4.1
1000-
2000
-
-
10
7
3
1
1
-
8
30
5.7
2000- 4000- 8000-
4000 8000 16,000 Total
1 - - 56
179
3 - - 135
2 1 56
1 26
13
13
14
4 - - 37
8 2 2 529
1.5 0.4 0.4 100
Percent
10.6
33.8
25.5
10.6
4.9
2.5
2.5
2'.6
7.0
100.0*
-------
The ratio of fibrillated fibers to nonfibrillated fibers was 22 percent
in the case of NWC 11 as compared to 30 percent for NWC 13. An average number
of about 10 individual particles per fibrillated fiber were observed for both
sets of data.- In general, the distributions for the two tests were quite
similar. Therefore, it appeared reasonable to assume a combination of the
associated micron fiber data for the purpose of the present criteria analysis.
A comparative plot of the integrated micron fiber characteristics encompassing
a total of 1026 fibers is shown in Figure 4. Although not indicated, the
lower limits for the plots of Figure 4 were respectively 0.4 microns for
diameter, 2 microns for length and 3 for length to diameter ratio.
With reference to Tables 2 and 3, the average frequency of occurrence for
NWC 11 and NWC 13 of single fibers in the micron fiber domain is 44 percent as
compared to 6 percent for lengths greater than or equal to 1 mm, or a ratio of
7.3. To account for incomplete data reduction of the fibrillated fibers, it
appears reasonable to increase this ratio to 10.
It is noted that a predominant portion of the observed particles in the
micron domain of diameters less than 3 microns and lengths less than 80
microns were associated with fibrillated fibers. In the data reduction of the
NWC sticky paper records location of isolated particles of such dimensions was
extremely difficult since the frequency of occurrence was quite small. It is
quite probable that particles of this size with very low settling velocities
would have been dispersed to significant distances downrange before being
deposited on the ground.
A study by means of SEM photography of free carbon fibers collected
during the DFG tests yielded an insight into the causes of fibrillation
effects. Examples of the different manifestations of the fibrillation phe-
nomena are shown in Figures 5 and 6 with arbitrary categorization of the types
of effects. These photographs offer striking evidence of the spectrum of
oxidation effects caused by the fire environment leading to what has been
designated as fibrillation phenomena and indicating conclusively a source of
micron size fibers from a parent single carbon fiber.
It was of interest to study the pattern of separation of single fibrils
of significant lengths. The result in one case is reflected by the sequence
of photographs presented in Figure 7, each corresponding to 3000X magnifica-
tion with the indicated vertical scale of 2 microns and horizontal scale of
50 microns applicable similarly to each photograph. The overall length
covered was about 250 microns. Each photograph is essentially an extension
at the left of the photograph immediately adjacent and directly below it with
a small overlap for continuity and identification.
Separation of the two fibrils in the uppermost photograph appear to con-
tinue over a length of about 100 microns until the advent of a third fibril
in the middle photograph. Subsequently the three fibrils merge within a
length of about 125 microns with evidence only of a single fine line of sepa-
ration at the termination in the bottom photograph. At the far right of the
bottom photograph, a fiber is noted with an average diameter of about 1 micron
and length of about 20 microns. However, over a length of about 3 microns at
each end the fiber diameter is gradually reduced down to a value of a small
461
-------
DIAMETER SPECTRUM
LENGTH SPECTRUM
30
25
P
Z
Sw
£
RELATIVE OCCURf
0 5
6
0
*
1
30
25
5 20
£
8
|«
u)
>
P.o
E
5
0
•
0
0
(0 3
10 '
DIAMETER .MICBONSI
LENGTH IMICKONSI
LENGTH TO
DIAMETER |
RATIO 5
30 40 SO
LENGTH TO DIAMETER RATIO
Figure 4. Micron Fiber Characteristics
-------
SINGULAR
AREA
HOLLOW TRUNK
FLAKING
30 M
Figure 5. Representative Fibrillation Effects - I
-------
EYE-OF-THE-NEEDLE
SUBMICRON FIBER
(D = 0.4n, L = 8.7 p)
Figure 6. Representative Fibrillation Effects - II
-------
Figure 7. Fibrillation Phenomena Over Extended Length
-------
fraction of a micron. This manifestation of diameter reductionjat the ends
is quite characteristic of the micron size fibers associated witih the fibril-
lated particles evaluated in the present study. . i
The foregoing results indicate that considerable degradation of the fiber
structure may be attributed to the high temperature fire environment. There
appeared to be singular areas where preferential oxidation occurred with
frequent irregular patterns in the fibril evolution. Studies of carbon fiber
microstructure8"12 indicate the existence of various types of precursor
defects (inorganic particulate, irregular voids) and graphite fiber flaws
(cavities, pockets of low crystalline density) which can affect oxidation
resistance. In addition, sodium impurities can cause catalytic oxidation in
carbon.
Micron fiber criteria were developed on the basis of the following meth-
odology: (1) assume NASA criteria1^ for single fibers with lengths greater
than or equal to 1 mm (NL ^ 1 mm)» (2) determine the frequency ratio (FR) of
micron fibers to single fibers with L > 1 mm, (3) estimate an enhancement
factor (EF) to account for data base limitations, and (4) multiply the re-
spective factors to yield the micron fiber number as follows:
NMF = (NL > 1 mm) X (FR) X (EF)
As noted earlier, the frequency ratio of micron fibers to single fibers of
lengths greater than or equal to 1 mm is estimated to be a factor of 10.
However, there are various limitations and uncertainties regarding the data
base available for the purpose of establishing this ratio.
A number of these limitations are briefly outlined as follows:
• Considerable difficulty was encountered in the data reduction
of isolated micron fibers due to the sparcity of occurrence to
the extent that data of this nature was essentially discounted.
• Analytical results encompass only data from close-in ranges
with no basis for judgement regarding downrange characteristics.
• Fibrillated fibers constituted the principal source of micron
fiber data with the relative frequence of occurrence of high
density micron fiber regions as,somewhat indefinite.
• Micron fiber criteria have been evaluated only on the basis of
NWC test data.
• Prediction of the extent of fibrillation effects associated
with aircraft accident scenarios is highly uncertain.
• Potential impact of significant diameter reductions at the micron
fiber ends may warrant consideration.
468
-------
• Data collection technique involving pressure of protective
acetate cover sheet over sticky paper adhesive surface may have
contributed toward separation of micron fibers from parent
fibrillated particles.
• Appropriate scaling factors for increased composite mass and
complex structural configurations are unavailable.
• Micron fiber source enhancement due to wind conditions,
explosions, turbulence and mechanical disturbances has not
been evaluated.
On the basis of the foregoing limitations, it appears reasonable to
introduce an enhancement factor of 10 in the frequency ratio of micron fibers
to single fibers with lengths greater than or equal to 1 mm.
Micron fiber criteria estimates based on the analyses of the present
study are presented in Figure 8. The total number of micron fibers per kilo-
gram mass of carbon fiber released is specified as 5 x 1011, with a corre-
sponding micron fiber mass fraction of carbon fiber released as 5 percent.
The spectral distribution of micron fiber dimensions reflects a relatively
uniform pattern over the respective diameter and length intervals.
The criteria values of Figure 8 constitute a description of the micron
fibers generated at the source during an aircraft accident involving a fire
only. It appeared of interest to evaluate an extreme case estimate of the
potential exposure to the micron fiber plume propagating downwind. Results
of the upper limit estimates are shown in Figure 9.
The mass of carbon fiber exposed to the fire was assumed as 1000 kg re-
sulting in a total number of 5 x 1012 micron fibers released. A schematic of
the carbon fiber plume profile is shown in Figure 9. For the purpose of the
present analysis no consideration is given to the particulate rainout occurr-
ing in the close-in regions, with attention focussed principally on exposures
beyond the plume cross-section designated in Figure 9 as downrange source
area. No loss of micron fibers is considered for the close-in areas with the
total source of 5 x 1012 micron fibers assumed available for propagation down-
range. In addition, reduction of concentration levels due to dispersion of
the fiber cloud is neglected.
The peak carbon fiber concentration and exposure levels were estimated as:
(CCF>max = 5.3 x 10* f/m3
3'2 x 1C)8
Corresponding values for the OSHA asbestos standard3 are:
C - 2 x 106 f/m3 (8-hr time weighted average)
469
-------
• MICRON FIBER FREQUENCY RATIO RELATIVE TO SINGLE FIBER LENGTHS > 1MM 10
• ENHANCEMENT FACTOR TO ACCOUNT FOR LIMITATIONS AND UNCERTAINTIES 10
• MICRON FIBERS PER KILOGRAM MASS OF CARBON FIBER RELEASED
- ASSUME NASA VALUE FOR LENGTHS > 1MM = 5 X 109 FIBERS
- MULTIPLY BY MICRON FIBER FREQUENCY RATIO AND ENHANCEMENT FACTOR
NUMBER OF MICRON FIBERS = 15 X 109] X flOj X flOJ = 5.X1011
• MICRON FIBER DIMENSIONS
•xj
o
LENGTH
(MICRONS)
2-10
10-20
20-30
30-40
40-60
60-80
PERCENT
OF TOTAL
10
24
21
16
16
13
DIAMETER
(MICRONS)
0.4-1.0
1.0-1.5
1.5-2.0
2.0 - 2.5
2.5 - 3.0
—
PERCENT
OF TOTAL
21
27
20
23
9
—
MICRON FIBER MASS PER KILOGRAM OF CARBON FIBER RELEASED
- AVERAGE MASS PER FIBER: M = J D2 L p = f \1.5 X 10~4) \3Q X 10"4) ^j.8J = 1 X TO'10 GM
- TOTAL MICRON FIBER MASS: My = fs X 1011J M X 10~10j =50GM
- MASS FRACTION OF CF RELEASED: 5 PERCENT
Figure 8. Micron Fiber Criteria Estimates
-------
MASS OF CF EXPOSED TO FIRE
MASS OF CF RELEASED (1%)
NUMBER OF MICRON FIBERS RELEASED
TOTAL MICRON FIBERS RELEASED
Nf
CONCENTRATION C -
Nf „ FIBER NUMBER
- Of = SOURCE AREA
Vw = WIND VELOCITY
tb = BURN TIME
PARAMETER ASSUMPTIONS
D =200M V =0.5M/SEC tb=60SEC
1000 KG
10 KG
5X 1011 PER KG
J2
CARBON FIBER PLUME PROFILE
5X 10(
CARBON FIBER
COMPOSITE
STRUCTURE DOWNRANGE
SOURCE AREA
WIND
VELOCITY
SETTLING
VELOCITY
CONCENTRATION =
f(200)2 (0.5)(60)
c o
5.3 X 106 F/M3
EXPOSURE = CONCENTRATION X BURN TIME
F-S
= (5.3 X 106)(60) = 3.2 X 108
M
fi F
OSHA ASBESTOS STANDARD : CONCENTRATION 2x10°-^;
EXPOSURE
5.8 x 1010 — PER 8 - HR DAY (CUMULATIVE)
M3
Figure 9. Upper Limit Estimate of Micron Fiber Exposure
-------
1 x 107 f/m3 (ceiling concentration)
EAS = 5'8 x 10l° f~s/m3 Per 8~nr dav (cumulative)
The OSHA asbestos exposure level is based on a permissible concentration level
of 2 x 106 f/m3 as a time-weighted average over a single 8-hour period (2.9 x
101* sec) . The exposure level is cumulative since OSHA criteria permit similar
exposures for each successive work day.
The upper limit of the micron carbon fiber concentration level is only
about half the permissible OSHA asbestos ceiling concentration level. Consid-
eration of factors such as higher wind velocities, longer burn times and
downrange plume dispersion would lead to values even lower than the OSHA
asbestos standard. It appears reasonable to conclude that the micron fiber
exposure levels resulting from an aircraft accident would be substantially
lower than the OSHA standard criteria for asbestos.
ACKNOWLEDGMENTS
The support of this research by NASA Langley Research Center is grate-
fully acknowledged. The author would like to express his appreciation to
V. L. Bell and R. A. Pride of NASA Langley for their helpful suggestions,
encouragement and cooperation toward development of the data base.
REFERENCES
1. Lieberman, P. Chovit, A. R. Chovit, B. Sussholz, and H. F. Korman. Data
Reduction and Analysis of Graphite Fiber Release Experiments. (TRW
Defense and Space Systems Group, NASA Contract NAS 1-15465.) NASA
CR-159032, 1979.
2. Pride, R. A. Large Scale Fiber Release and Equipment Exposure Experi-
ments. NASA Conference Publication 2119, 1980, pp. 101-136.
3. Occupational Safety and Health Administration. General Industry Safety
and Health Standards. OSHA 2206, Code of Federal Regulations, Title 29,
Part 1910.1001, Revised January 1976.
4. Occupational Safety and Health Administration. Occupational Exposure to
Asbestos. Federal Register, Part II, 9 October 1975.
5. National Institute for Occupational Safety and Health. Revised Recom-
mended Asbestos Standard. DHEW (NIOSH) Publication No. 77-169, December
1976.
6. National Institute for Occupational Safety and Health. Criteria for a
Recommended Standard Occupational Exposure to Fibrous Glass. DHEW
(NIOSH) Publication No. 77-152, April 1977.
472
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7. British Advisory Committee on Asbestos of the Health and Safety Commis-
sion and Ministers. Volume 1: Final Report of the Advisory Committee,
and Volume 2: Papers Prepared for the Advisory Committee. 1979.
8. Barnet, F. Robert and Marriner K. Norr. Carbon Fiber Etching in an
Oxygen Plasma. Carbon, Volume 11, 1973, pp. 281-288.
9. Barnet, F. Robert and Marriner K. Norr. A Three-Dimensional Structural
Model for a High Modulus Pan-Based Carbon Fiber. Naval Ordnance Labora-
tory NOLTR 73-154, June 1974.
10. Sharp, J. V. and S. G. Burnay. High-Voltage Electron Microscopy of
Internal Defects in Carbon Fibers. International Carbon Fibers Confer-
ence, London, 2-4 February 1971, Paper 10, pp. 68-72.
11. Johnson, J. W. and D. J. Thome. Effects of Internal Polymer Flaws on
Strength of Carbon Fibers Prepared from Acrylic Precursor. Carbon,
Volume 7, 1969, pp. 659-661.
12. Thorne, D. J. Distribution of Internal Flaws in Acrylic Fibers.
Journal of Applied Polymer Science, Volume 14, 1980, pp. 103-113.
13. Bell, Vernon L. Release of Carbon Fibers from Burning Composites.
NASA Conference Publication 2119, 1980, pp. 29-57.
473
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DISCUSSION ON GRAPHITE FIBERS
REMARK (Dr. Corn): I am associated with the John Hopkins University. My
comments are relative to the last presentation which I found an
interesting diversion in science fiction until you invoked the
OSHA standards for asbestos. You must be aware, Dr. Sussholz, that
the OSHA standard is one of using a surrogate for the total number
of asbestos fibers present. It is implicit that the standard
sample should be used and analyzed in a standard manner. You
sampled in a nonstandard grossly inefficient manner for precisely
the inhalable particles associated with asbestos risk. You cannot
expect to capture those by a sedimentation method or a sticky
paper method. You then superimposed upon that extrapolation of
values what I would call "finagle factors" and an interesting
construct, all of which I am perfectly willing to listen to. But
do not then compare that to a meaningful standard for the assess-
ment of risk to inhalation of fibers. I would submit here that the
analysis is just totally incorrect.
REMARK (Dr. Sussholz): I guess my concluding remarks, which attempted to
reflect the uncertainties and the application of the results with
referencej to the general areas of interest here, were insufficient
to allay//the fears of this gentlemen. I cannot disagree with any
of the comments you made;, you are free to your own opinion. This
was the best we could do under the circumstances. It turned out
to be the first study of its nature. And in any manner that
additional work can be supported in any way anywhere at all, that
is a wonderful idea.
QUESTION (Mr. Wagner): I am from Dupont. Dr. Sussholz, do you have any
data on the number of micron size particles generated in machining
or cutting of a carbon fiber reinforced composite?
ANSWER: (Dr. Sussholz): Not that I am aware of. We do not have data of
any nature along those lines, and I am not aware of a study that
has been performed where this type of information was of prime
interest.
474
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CROSS-SECTIONAL MEDICAL STUDY OF WOLLASTONITE WORKERS
by
Dr. Brian Boehlecke, Dr. D.M. Shasby, Mr. M.R. Petersen,
Dr. T.K. Hodous, and Dr. J.A. Merchant*
National Institute for Occupational Safety and Health
Morgantown, West Virginia 26505
ABSTRACT
Wollastonite is a fibrous monocalcium silicate with widespread use in ceramics
and as a substitute for asbestos. Workers at the only U.S. wollastonite mine
and mill were studied with spirometry using air and 80% helium-20% 02, chest
x-ray, physical examination, and respiratory questionnaire. Diffusing capacity
of the lung (D,ro) was measured in 23 workers with over 15 years' exposure.
Overall, 104 men(72% of all those with at least 1 year of exposure) were stud-
ied. Air samples were collected at the work site on Millipore filters and fiber
counts performed with phase contrast microscopy. An exposure index was calcu-
lated by multiplying mean count of fibers (greater than 5 micrometers in length)
per cc x years of work.
Symptoms of chronic bronchitis were present in 23% of smokers and ex-smokers
and in 9% of non-smokers. However, there was no association of prevalence of
bronchitis with increasing exposure index. A reduction in forced vital capaci-
ty (FVC) below the predicted range was found in only 1 worker. Although 20%
of smokers and ex-smokers had a forced expired volume in 1 second (FEV^) less
than 70% of FVC, no significant correlation of obstructive impairment or forced
expiratory flow at 50% of vital capacity with exposure index was found for air
or helium-02 spirometry. One subject who has polycythemia vera had an abnormal
DTr_. Four men without other abnormalities had chest x-rays showing Category 1,
type q, rounded opacities. No irregular opacities or pleural plaques were noted.
Five workers, all current or past smokers, had crepitations in the lungs, not
associated with x-ray changes. Wollastonite is similar to asbestos, but we were
unable to demonstrate the usual stigmata of asbestos exposure. Because only 36%
of men studied had over 15 years' exposure, further followup is needed to deter-
mine if wollastonite is truly less hazardous than asbestos.
*Presented by Dr. Brian Boehlecke. This study may be found in Dust and Disease,
"Respiratory Morbidity of Workers Exposed to Wollastonite through Mining and
Milling." John Dement and Richard Lemmens (Eds.), Pathotox Publishers, 2405
Bond Street, Park Forest South, IL 60466, (1979) p. 251-256.
475
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DISCUSSION ON WOLLASTONITE
REMARK (Mr. Clifton): I am from the U.S. Bureau of Mines.
I see you are looking for substitutes for asbestos all over the place
and it is very nice to find one that has many of the same properties
as asbestos with no apparent health effects. A word of caution,
though. Some of these substitute materials are very finite resources
and reserves, which means that if they were purported to replace
asbestos in large areas, the cost could go up astronomically. Wol-
lastonite happens to be one with very small reserves and resources.
QUESTION (Dr. Gross): I am from the Industrial Health Foundation.
While you were talking I looked at a graph of the relationship of alveolar
deposition, that is deposition in the air spaces against the diameter
and length of the fiber. As I understand it, the average wollastonite
fiber was in excess of 2 micrometers in diameter, is that correct?
ANSWER (Dr. Boehlecke) : No. Two and a half micrometers in length, and
0.22 micrometers in diameter.
REMARK (Dr. Gross): In that case, I do not have any information on that. But
if it had been 2 micrometers in diameter, it would have had a deposi-
tion in the air space of only 2 percent.
REMARK (Dr. Boehlecke): No, it is 0.22.
476
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ENDEMIC PLEURAL DISEASE IN RELATION TO
ZEOLITE EXPOSURE
by
I
Arthur N. Rohl, Ph.D.
Mount Sinai School of Medicine of the
City University of New York
New York, New York
ABSTRACT
Pleural mesothelioma, lung cancer, pleural and parenctyymal fibrosis appear to
be endemic in an agricultural area of Cappadocia, Turkey. Initial observations
Indicate that asbestos does not occur nor is it used. However, fibrous zeolite
minerals appear to be widely distributed there. The verification of this
supposition may provide information on a troubling and unresolved public
health question. With the recognition of significant hazards associated with
exposure to asbestos, caution has been suggested on the basis that substitute
commercial fibers may have similar biological activity. This concern is rein-
forced by Stanton's hypothesis that the toxlcity of inorganic fibers depends
more on their shape and size than on physical-chemical factors. Human ex-
perience bearing on the question for evaluation has been heretofor lacking.
The affected area was visited and a large number and variety of environmental
samples, as well as lung tissue of individuals with mesothelioma and other
thoracic disease were collected. These samples are being analyzed to estab-
lish the mineral assemblages present to permit correlation of observed dis-
ease with microparticulate exposures which may have occurred.
More than 50 cases of pleural mesothelioma have been reported during
the period from 1974-78 in a relatively small area of Turkey, centered in and
around the villages of Karain and TuzkBy, in the province of Cappadocia. The
incidence of malignant pleural mesothelioma in this area for exceeds any rate
for any population not known to be asbestos-exposed. Moreover, calcified
plaques, pleural thickening and parenchymal scarring are also prevalent in
these populations. Plaques and scarring are often stigmata of exposure to
asbestos, leading to mesothelioma. No outcroppings of asbestos-containing
rocks, nor asbestos mines or industries, are known to exist in this area.
However, another group of silicate minerals is present. This group of min-
erals is called zeolites and it Includes fibrous types, having fiber dimen-
sions similar to some asbestos fibers. The area of Karain and Tuzkoy is
covered with volcanic tuffs, which are altered in places to form a range of
zeolite minerals. The volcanic tuff consists principally of glass fragments
(including glass fibers), quartz, plagioclase feldspar and pyroxene minerals.
In addition to zeolites, other alteration products such as montmorillonite,
cristobalite and tridymite are found. The tuffs in this area of Turkey are
477
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generally soft and friable and are subject to wind erosion. The tuff building
stones are hand-cut from local quarries located in hills and cliffs adjacent
to the different villages for construction purposes. A large proportion of the
houses in Karain are actually caves, excavated by hand from the soft tuffaceous
rock. The village of Karain itself abuts the steep valley wall which overlooks
the town. In addition to houses, a number of holes and caves have been ex-
cavated in the nearby outcropping of tuff for use as animal pens, food storage
areas, and fodder storage areas. Pigeon excrement, the. only fertilizer used,
is collected by villagers from the nest-holes in the tuff. In the homes, and in
the excavated caves, and in agricultural pursuits, constant contact is made with
settled dusts, soils and rock surfaces. The floors of the homes tend to be the
soil surface. Also, in many homes, the use of pulverized white soil, locally
collected for whitewash is also common. The roads in the area are for the
most part unpaved. Winds, vehicular traffic, and other activities in this
semiarid climate results in the generation of large amounts of airborne dust.
Agriculture and animal husbandry are virtually the only occupations. The
effect of these circumstances is to expose the populations of the villages to
high levels of airborne dust, originating from the host rock, throughout their
entire lives. While some villages have the appearance of being dustier than
others, the observed differences in levels of pleural diseases among the villages
in the area may be the result of either differences in the kinds and amounts of
dust exposures, or both. The mineralogical characterization, both quantitative
and qualitative, of these materials affords an important foundation for the eval-
uation of the biological problems.
With the cooperation of the Turkish scientists studying the Cappadocia
situation, we visited the area and obtained a large number and variety of rock
and environmental samples such as house and road dust, local whitewash, per-
tinent geological samples, building stone as well as lung tissue of individuals
with mesothelioma and other thoracic disease. These samples are being analyzed
to establish the exact mineral assemblages present and to permit correlation of
observed disease with dust exposures which may have occurred.
The incidence of mesothelioma is of particular interest since this
cancer has been considered to be a "marker disease" for asbestos exposure. Re-
cent studies suggest that most mesotheliomas (80-95 percent) can be traced to
asbestos exposure. (1) In the village of Karain, in Cappadocia, with a total
population of 604, there were 11 deaths due to pleural mesothelioma of a total
of 18 in 1974. In the previous five years, 25 pleural mesotheliomas were re-
ported from the same village. (2) On the basis of a study carried out in a
nearby village, Tuzkoy, with a population of about 3,000, it was found that the
incidence of pleural mesothelioma is at least 6.5 patients per year, or about
one thousand times more than expected. (3) It is of interest to note that
these data were accumulated by the Chest Service of a large Turkish medical
center, so that peritoneal mesothelioma may remain largely unreported, although
it is known to have occurred. It is possible that even this extraordinary
finding may be significantly underestimating the true incidence of mesothelioma
because of the remoteness of the area and the general lack of medical services
in the region.
478
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The results of this study may be expected to provide information re-
garding the validity of the Stanton hypothesis. (4,5,6) Stanton suggested,
based on experimental observations, that the exposure of animals to fibrous
materials produces greater cancer risk than the exposure to identical mater-
ials which are non-fibrous. For example, the intrapleural injection of fibrous
materials of diverse types and size distributions into animals produces mal-
ignant tumors significantly related to fiber shape and a narrow size range of
fibers. It is stated that the "simplist incriminating feature for both car-
cinogenesis and fibrogenesis seems to be a durable fibrous shape, perhaps in a
narrow size range. (6) Stanton observed that long, thin fibers produced pro-
portionally more mesotheliomas when implanted in the rat. In addition, the
experiments of Pott and Friedrichs, (7), and Pott, Huth and Friedrichs (8)
indicated that the carcinogenic (mesothelioma) potency of a mineral depended
upon shape factors, the fibrous forms tending to be more carcinogenic. There-
fore it appears reasonable that the focus for search of a physical etiologic
agent in association with mesothelioma should fall on mineral fiber. For
one fiber, asbestos, documentation concerning the relation to mesothelioma is
extensive. In Turkey, since endemic mesothelioma and other pleural diseases
occur without apparent asbestos exposure, other mineral fibers, possibly fib-
rous zeolites, may be implicated. An important objective will be to confirm
the alleged absence of asbestos in environmental samples. Since there are no
asbestos mines or mills and since there is no use of commercial asbestos prod-
ucts by the villagers, it has been argued that asbestos is not the etiologic
agent. This argument is based on the speculation that the geological nature
and history of the area are highly unfavorable for the occurrence of asbestos
deposits, commercial or otherwise. However, Cappadocia covers an area of
over 1,500 square kilometers, mostly remote and inaccessible. The geology is
highly complex and has not been studied in sufficient detail to fully exclude
the possibility that asbestos minerals may occur in the area. They may or may
not occur in or near the villages. They may be exogeneous, brought from dis-
tant sources. For example, it is common practice in the region for the villagers
to stucco or whitewash their dwellings for hygienic and esthetic purposes.
Preparation, application and removal of the whitewash produces visable dust, and
surface erosion of the whitewash may add to this dust. Each village obtains its
own supply of whitewash from various, unknown sources. Asbestos minerals may
occur with some types of light-colored rocks, such as metamorphosed limestones.
ZEOLITES
Zeolites are hydrated aluminum silicates, with alkaline metal and al-
kaline earths substituting within the framework structure. The water of hydra-
tion is both variable and reversible, and cations may readily substitute within
the structure. The corners of the silica tetrahedron are shared, producing a
three-dimensional lattice, and substitution of aluminum for silicon in the
tetrahedra produces a charge imbalance imparting a negative charge to the
structure. About 40 naturally-occurring zeolites have been described and over
100 synthetic zeolites have been made for industrial applications. The latter
are commonly known by their commercial designation as "molecular selves."
479
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The physical-chemical properties of the zeolite minerals are extremely var-
iable. The mineral can easily be dehydrated and rehydrated; cations easily
substitute and re-enter the structure; the ion exchange capacity and the ability
to absorb various gases is enormous; an increase in the silicon to aluminum
ratio decreases cation substitution, but increases acid resistance and thermal
stability; the increase in silicon to aluminum ratios decreases cell dimen-
sions and external pore diameters, further altering the nature of molecular
interaction. The changes in physical-chemical properties of the zeolite min-
erals may affect their biological potential.
Zeolites naturally form by alteration of volcanic ash, which is
essentially glass. This alteration may occur either in saline alkaline lake
waters, or in areas where ground water is present and may percolate through
the sediments. Alkalies present in the volcanic debris are dissolved and
chemically react with the glass to form zeolite minerals. Zeolites naturally
occur in volcanic sediments throughout the United States. (9) Some of the
zeolite minerals are extraordinarily abundant and widespread. Karain and
TuzkHy pose the question whether natural zeolite minerals found in the rocks
and soils of Turkey, or in other areas of the world, possess the biological
potential to induce mesothelioma and other disease.
REFERENCES
1. Cochrane, J.C. and Webster, I. Mesothelioma in relation to asbestos fibre
exposure; a review of 70 serial cases. South African Med. Jour. 1978;
54:279-281.
2. Baris, Y.I, Sahin, A.A., Ozemi, M., Kerse, I., Ozen, E., Kolacan, B., Altinors,
M. and Goktepeli, A. An outbreak of pleural mesothelioma and chronic fibros-
ing pleurisy in the village of Karain/Urgup in Anatolia. Thorax 1978; 33:2:
181-192.
3. Artvinli, M. and Baris, Y.I. Malignant mesotheliomas in a small village in
the Anatolian region of Turkey: An epidemiclogic study. Jour. Natl. Cancer
Inst. 1979:63:17-22.
4. Stanton, F. F. and Wrench, C. Mechanisms of mesothelioma induction with
asbestos and fibrous glass. J. Natl. Cancer Inst. 1972:48:8:797-821.
5. Stanton, F.F., Layard, M., Tegeris, A., Miller, E., May, M. and Kent, E.
Carcinogenicity of fibrous glass: Pleural response in the rat in relation
to fiber dimension. J. Nat. Cancer Inst. 1977;58:3:587-603.
6. Stanton, F.F. and Wrench, C. Mechanisms of mesothelioma induction with
asbestos and fibrous glass. J. Natl. Cancer Inst. 1972;48:3:815.
7. Pott, F. and Friedrichs, K.H. Tumoren der Ratte nach i.-p Injektion faser-
formiger Staube. Naturwissenschaften 1972; 59:318.
480
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8. Pott, F., Huth, F. and Friedrichs, K.H. Tumorogenic effects of fibrous dusts
in experimental animals. Environ. Health Perspectives 1974;9:313-315.
9. Sand, L.B. and Mumpton, F.A. Natural zeolites, occurrences, properties, use.
Pergamon Press, N.T.C. p. 546.
481
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DISCUSSION ON ZEOLITES IN TURKEY
QUESTION (Dr. Rowe): Dr. Rohl, the mesothelloma that is prevalent in this
area of Turkey, is it all pleural mesothelioma or is there also
peritoneal mesothelioma?
ANSWER (Dr. Rohl): It is virtually all pleural mesothelioma. There are
one or two cases of peritoneal mesothelioma, but these may have been
largely overlooked because it is a remote, rural area of Turkey.
Modern medical services are practically unavailable. The only people
who come to Dr. Baris' chest clinic at Haceteppe University are those
with serious pleural disease. Those with other diseases may go
unobserved.
QUESTION (Mr. Dickinson): Yesterday, we heard that if you used asbestos cement
on roofing tiles and then collected water in cisterns you tended to
get asbestos fibers at times. You mentioned having taken samples of
house dust and road dust as well as white wash. Since this is a
desert area, essentially, water is a very scarce commodity, I would
hypothesize that probably villages would tend to have one water
source from which they would all drink. My question is whether the
same water source was available for all the villages or whether in
effect each one has a separate source and may be one of them was
contaminated and the others not?
ANSWER (Dr. Rohl): That was investigated. Although there are two water
sources, one well is the major source for the entire village of Karain,
and no agents were found in the water. It was analyzed for both
inorganic and organic contamination which might be responsible.
Although asbestos fibers were found by one investigator this has
not yet been confirmed.
REMARK (Dr. Wiley): I am from the University of Maryland. I would like to
stand behind what Mac Ross has said. I think that the evidence is
not at all conclusive that zeolites are the cause of the mesothe-
liomas. I would just like to point out that the sizes that you
mentioned, less than 0.25 microns in diameter and 3 microns in
length, are almost identical to the sizes of wollastonite particles
that were presented in the previous study. So that if indeed it is
a size and shape factor that is in the disease, we have a real
contradiction in the evidence here.
REMARK (Dr. Rohl): We have a whole string of ifs, ands, or buts. No one
said it is a simple question. It is going to take a lot of time.
It is a very complicated analytical matter, and the interpretation
of the results will also be very intricate.
REMARK (Dr. Langer): I wonder if I can add to this discussion. Perhaps
some other data will help shed light on this subject. Mt. Sinai
has a number of ongoing studies in our Laboratory which appear to
indicate the following: fibrous erionite has produced tumors
(mesotheliomas) in the bellies of mice. Mordenite fiber has not as
482
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yet. It produces pronounced scarring. This might have been predicted
by their aluminum: silicon ratios. Some species of fibrous zeolites
appear to be fibrogens, some possible carcinogens. Perhaps not all
of the zeolite minerals will be shown to be active. We need more
time and experiments to verify this.
We have also completed studies concerning the hemolytic potential of
these various materials. Again, the aluminum: silicon ratio has some
correlation with hemolytic potency. High silicon containing zeolites
are cytotoxic. These compounds are membrane active. Some of these
materials, because of their extraordinary cytotoxity, will not allow
cells to live long enough to undergo mutation and transformation.
Cancer will not be the outcome for these exposures.
There is a tremendous set of data that has been collected by the
IARC consulting group in Wales (PRU-Llandough): Wagner confirmed
the Turkish mesotheliomas; Fred Pooley confirmed the presence of
zeolite mineral species; Peter Elmes confirmed the clinical diseases;
Joe Skidmore, probably one of the best "dust11 men in the world, went
there and performed environmental measurements. When all of these
data were collected and looked at as a body of knowledge, the follow-
ing was found:(1) there occurs bonafide mesotheliomas; (2) in the
environment there exists a series of fibrous minerals. They are
zeolites; (3) the environmental measurements suggest the amount of
fiber that is actually in air is very small. These fibers are again
zeolites. Yet, what is the agent that is responsible for the meso- •
thelioma? Can small amounts of zeolite fiber produce mesothelioma?
We have done some work on the stucco that is used to whitewash the
insides of the Karain houses. They are derived from many sources of
rock and some of these sources may contain other mineral fibers.
These may be agents of disease as well.
There are other possibilities as well: I think it is much too early
for us to dismiss the possibility that a subspecies of erionite fiber
may produce mesothelioma; there may be some asbestos in the area.
QUESTION (Mr. Mill): I am from the Cabot Corporation. A common alteration
product of volcanic tuff is cristobalite which has biologic activity.
Was there any cristobalite in this tuff to your knowledge?
ANSWER (Dr. Rohl): Yes. Cristobalite was described in some of the samples.
QUESTION (Mr. Mill): And I would like to ask another question that is not about
Turkey. There is a very common zeolite mineral which to my knowledge
is not fibrous, in the American West, and that is clinoptilolite,
which is beginning to enjoy some commercial exploitation. Does any-
one know if this has been found to cause health problems?
ANSWER (Dr. Rohl): No, I do not think that has been studied with reference to
clinoptilolite. clinoptilolite does occur in the Turkish tuffs.
483
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REMARK (Dr. Langer): I would like to add to this. We have looked at
clinoptilolite in our membrane system and it is very active. It has
a "hemolytic" index or hemolytic potency which is almost equal to that
of quartz.
REMARK (Mr. Mill): Well, I'd like to make one other comment. Clinoptilolite
apparently is nonfibrous, and I find it difficult to accept this
Stanton hypothesis, as it is mentioned in the abstract, that it is
the geometry of these particles that determine their problems.
QUESTION (Mr. Merryman) : I am from the Dupont Company. I would like to ask
Dr. Langer what was the difference between the zeolite minerals
that did and di'd not produce mesotheliomas or tumors in the lab-
oratory different in shape in addition to their difference in chem-
ical structure?
ANSWER (Dr. Langer): I am from Mt. Sinai. There are marked differences
between erionite and mordenite. Erionite tends to be more "asbesti-
form", if I can use that term, than mordenite. Mordenite tends to
occur as long, flat, bladed crystals. If we were to look at its size
distribution characteristics, and compare it with erionite, erionite
would be more like an amphibole asbestos mineral, like amosite or
crocidolite, whereas the mordenite would be more like anthophyllite.
I add that amosite and crocidolite have produced mesotheliomas in
human populations whereas anthophyllite has not.
Mordenite tends to have less aluminum in the structure; therefore it
has less of the alkaline cations substituting in the structure. The
erionite tends to interact more with polar compounds (this has been
described in the literature extensively). Mordenite tends to be
more a silicon-rich, more "siliceous" if you like, and tends to
have chemistry more like quartz, or like the silica polymorphs.
Mordenite produces scarring in animals; erionite produces cancer.
QUESTION (Mr. Merryman): I gather then, that there is both a surface size
and a chemical effect possible. Can you expand on that? Does
there tend to be any data that indicate that you can have a chemical
effect independent of the size and shape effect?
ANSWER (Dr. Langer): Absolutely. The Stanton hypothesis suggests that
any fibrous inorganic dust which reaches the mesothelial surface
will induce a tumor response. Mesothelioma or fibrosarcoma may be
produced regardless of the chemistry and of the composition of the
fiber. Last night we had an extensive discussion of this in the
Talc Session. We talked about different mineral fibers and whether
or not each possessed certain inherent physical-chemical charac-
teristics which would distinguish among them in terms of biological
activity. I believe it is simplistic to assume that because a
material is a "fiber" that there is some extraordinary power to
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induce tumors. I do not think that is so. For example, we know
chrysotile degrades readily while in biological residence, and
amphibole fibers do not. Amphibole fibers deliver a dose to target
tissue which is the number of particles multiplied by the unit time
in residence in those tissues. Amphibole unit dose delivered to tissue
is therefore longer than for an equivalent amount of chrysotile.
Investigators have studied the activity of degraded chrysotile and
observed a markedly decrease of mesothelioma potency. Therefore, both
a changed, surface character and a degradation process both account for
markedly decreased carcinogenicity. What we were seeing is that
obviously fiber morphology is useful in terms in inhalation potential,
in terms of penetrating the airways, in terms of deposition at the
alveolar site. But once it is delivered to the target tissue, the
response would be dependent upon the characteristics of the material
Itself.
QUESTION (Dr. Reeves): I am from Wayne State University. I have yet to hear a
substantial answer to Malcolm Ross1 comment, specifically the dif-
ference between these two communities that seem to have the same
geological structure and the same availability of dust, and yet
the startling difference in mesothelioma incidence. I think that
might be quite significant. I also looked at your mortality or
morbidity data. Am I correct in remembering that there were seven
new cases of mesothelioma in a town of 3,000 every year?
ANSWER (Dr. Rohl): Seven.
QUESTION (Dr. Reeves): Seven cases. Now over a lifetime that would amount to
something like 15 percent of the population, perhaps 20 percent of
the population coming down with the single disease of mesothelioma.
Now this is such a startling incidence that I just cannot understand
that this could have remained undetected throughout history. This
is one of the oldest inhabited areas of the world.
ANSWER (Dr. Rohl): And one of the most primitive, too.
REMARK (Dr. Reeves): No, it was not; today it is, but at a time of Alexander
the Great and so forth —
REMARK (Dr. Rohl): They did not have pathologists then.
REMARK (Dr. Reeves): These were the most cultured regions of the world.
I would have expected someone like Hippocrates to notice.
REMARK (Dr. Rohl): Maybe he did, but we have no record of it.
REMARK (Dr. Langer): Dr. Reeves, I believe the name Karain comes from the
Turkish which means "pain in the belly". Karain has a peculiar folk
legend which states that "anyone from Karain who develops a pain in
the side, soon his shoulder drops and he dies." This is the classical
clinical syndrome for mesothelioma. But you are quite correct. It
has been noted for a very long time that people from this area died
485
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with these strange chest maladies. And you are also correct, that
the incidence is quite extraordinary.
We find no differences between our data and those of Fred Mumpton
from SUNY: the same fibrous zeolites are present in the soils and
dusts of villages with mesothelioma, and those without mesothelioma.
Again, it may be a special subspecies of erionite or the presence of
other fibrous minerals of great biological activity. Yet, we are
still examining these specimens very carefully. X-ray diffraction
shows the same basic mineral population in both localities. But
there may be some specific fiber that occurs in Karain that is
different from those which occur elsewhere.
If you take "active sites" on the surface of zeolite minerals and you
block them with certain cationic species, I can assure you they will
not be biologically active. But those of you who know zeolites, who
know how active these materials are, how well it binds with various
cations, will understand how active these minerals can be. These
are wonderful compounds. However, if you inhale these particles,
their activity does not stop. The activity may go on, degrading
proteins and denaturing proteins in young tissue.
QUESTION (Mr. Wideland): I am a geologist from the University of Minnesota.
I have a medical question which I ask out of ignorance. Has your
laboratory or any other laboratories attempted to identify the
mineral species in lung tissue of these people who have died from
mesothelioma?
ANSWER (Dr. Rohl): We are working on that. We collected lung tissues from
patients of Dr. Harris' with mesotheliomas and we are investigating
the types and amounts of the minerals in those tissues. That will
be a very important factor in interpreting the results.
QUESTION (Mr. Wideland): In my casual reading of the medical literature there
does not seem to be a discussion of the possibility of ever locating
a specific fiber that you could pin down to having triggered a
carcinoma. Is that out of the range of possibilities?
ANSWER (Dr. Rohl): Well, identifying likely candidates would be an important
first step. After the likely candidate is identified, then further
animal experimentation would have to be done to find out if it does
produce the same disease.
QUESTION (Mr. Ross): A couple of points. First, I do not have the ref-
erence, but I believe that Pooley has identified fibrous zeolites.
I have to refresh my memory, but I believe Karain, a very isolated
town, is the town with a very~Tiigh incidence of mesothelioma", of~
five or six a year. TuzkSy has much fewer cases. I do not have the
number, but Tuzkoy has much fewer mesotheliomas than Karain which is
not quite as isolated a city as Karain is. But one of the things
that intrigued me in the Baris reports, is that in all the deaths he
486
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reported not one, I believe, was lung cancer. The males smoked.
Now If you look at asbestos-related disease you see a very high
correlation in a cohort mesothelioma with lung cancer. With
asbestos workers—you do not find them all dying just of meso-
thelioma or all dying just of lung cancer. It surprises me that
there was no reported lung cancer in this group of individuals.
I defer to the medical people, but would this suggest a hereditary
implication?
Going back to what I said, it is all very fine to do some good
straight science on this, but when you do a little bit of science
and very poor science and then you rush out to an industry and say
you are going to kill the workers because you are using zeolites
in your refining process, when that zeolite happens to be a synthetic
zeolite that is not fibrous, the whole work force is put into a
paranoia. Zeolites are a very large mineral group. And most zeolites
are not fibrous. One person got a hold of a newspaper article
and said we can not have the missile sites in Nevada because it will
dig up the ground and all the zeolites will come out. So the whole
southwest United States is full of zeolites which I call evil rocks.
And so we take a very preliminary scientific investigation and scare
half the United States. I do not think that is being very wise,
particularly when the zeolite industry is out here, and 90 percent
of the industry is out for cleaning up our environment.
REMARK (Dr. Rohl): One thing that I forgot to mention, there is lung
cancer in both Karain and Tuzkoy. The men in Turkey smoke; both
populations smoke. The women do not. But there is no difference in
the rates of mesotheliomas among men and women.
487
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CHEMICAL DETOXIFICATION OF ASBESTOS FIBERS
by
Earl S. Flowers, Ph.D.
Flow General Incorporated
McLean, Virginia
ABSTRACT
Exposure to asbestos materials is associated with a variety of biologic re-
sponses which include ferruginous body formation, chronic flbrosing processes,
and development of cancers. Formation of a ferruginous body is an early re-
sponse of tissues to asbestos, and a variety of such bodies involving deposi-
tion of iron containing materials on the fiber have been described. One type
of ferruginous body is formed by the deposition of inorganic iron on the fiber
surface. Acting on the premise that the addition of ferric oxides or other
metal oxides to asbestos would detoxify silicates and other toxic sites on the
fiber, several metal micelle forms of asbestos, including chrysotile, amosite,
crocidolite, and anthophyllite have been prepared. Biologic testing of iron
micelle forms of chrysotile and amosite show that the treatment with iron salts
decreases the cytotoxity of these forms of asbestos when compared with untreated
materials. The treatment of chrysotile with an iron salt also decreases hemo-
lytic activity and adverse effects on membrane permeability of cells. Testing
of the iron treated chrysotile in a variety of applications using Grades ranging
from AAA to 7 RF 99 in quality indicates that the treated asbestos retains de-
sirable physical properties and can substitute for asbestos in all its current
applications. The chemical treatment has been extended to show that metal oxides
of cobalt, chromium, manganese, aluminum, and copper also add to an asbestos
fiber.
Exposure to asbestos in the environment is associated with increased risk of
developing chronic fibrosis in the lungs and two forms of cancer, bronchiogenic
carcinoma and mesothelioma. Asbestos has been characterized as an unavoidably
unsafe material, but its desirable physical properties including heat resistance,
reinforcing strength, chemical resistance, flow characterization and versatility
in applications including cements, boards, papers, textiles, friction materials
and numerous other products has supported the continued and essential use of
asbestos minerals. Considerable efforts have been made to find substitutes for
the use of asbestos in its varied applications, but these efforts have met with
limited success. Invariably, proposed substitutes do not measure up to the use
of asbestos itself, or there are considerable costs that make use of the substi-
489
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tute prohibitive. One approach to this issue is to develop a substitute by
chemical detoxification of asbestos fibers. The objectives of this report are
to discuss the basis for chemical detoxification of the asbestos surface, to
present initial results of in vitro tests of treated materials, and to discuss
the effects of chemical treatment on the desirable attributes of asbestos.
The most hazardous asbestos fibers are those characterized as being deposi-
ted in the alveoli. Once deposited at critical tissue sites, asbestos produces •
a variety of responses including irritation of cells and tissues, increased
oxygen consumption, formation of ferruginous bodies, chronic fibrosis, an in-
creased risk of bronchiogenic carcinoma, and an increased risk of developing
mesothelioma. In 1974,1 I developed a hypothesis that these various responses
to asbestos were related. Silicate groups on the asbestos surface were charac- .
terized as active sites for formation of ferruginous deposits, and the leaching
of magnesium ions from the surface was identified as being involved in some of
the toxic effects.
Figure 1, adapted from my paper in 1974,l summarizes the hypothesis concern-
ing the relationship between exposure to asbestos, ferruginous body formation,
chronic fibrosing processes, and carcinomas. A sequence of dependent events
is thought to occur leading to increasingly adverse toxic effects. The under-
lying mechanisms are depicted as involving two independent pathways. In one
pathway, after phagocytosis and fiber encapsulation, a ferruginous body is
formed consisting primarily of substances containing ferric oxides, such as
ferritin, hemosiderin, or inorganic ferric hydroxides. The driving force for
deposition of ferric containing species is the presence of electronegative sites
produced by formation of hydrated silicates on the asbestos surface. The re-
moval of ferric ions in the formation of a ferruginous body requires the oxi-
dation of ferrous ions to replace the ferric ions in solutions and to reestab-
lish redox equilibrium. This results in an increased glycolysis as indicated
by increased oxygen consumption by tissues exposed to asbestos. Excessive
glycolysis leads to release of a fibrogenic factor characterized by Heppleston2
as possibly a galactan. This factor induces an increased rynthesis of elastic
fibers such as collagen at tissues which are remote from the site of deposition
of the asbestos fiber.
In Figure 2, the synthesis of collagen requires an oxidation of proline in
protocollagen by molecular oxygen with reduction by a reducing cofactor to form
hydroxyproline. This converts protocollagen to a more hydrophilic collagen
and frees the RNA-template for continued production of protocollagen. Thus,
continued release of a fibrogenic factor induced by increased glycolysis stimu-
lates a chronic production of fibrous protein or chronic fibrosing processes.
In Figure 1, the significance of the chronic fibrosing processes is inhibi-
tion of reductases leading to asbestos acting as a cocarcinogen in producing bron-
chiogenic carcinoma. This decrease in the availability of reducing cofactors
favors production of stable epoxides derived from toxic products of combustion,
synthetic toxins or natural products. Another cocarcinogenic mechanism for
producing an increased risk of carcinoma is the disruption of membranes by the
mechanical irritation of cells and tissues. The resulting increase in membrane
permeability would provide greater access for carcinogens and other toxic agents.
Finaily, another cocarcinogenic mechanism is by transport of a carcinogenic
490
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Increased
Giycolysls
\O
Release of a
Fibrogenic
Factor
Collagen
Synthesis
Inhalation of
Asbestos Ousts
Leaching of
Magnesium
Ions
rH OtoA
Transition
Phagocytosis & Fiber
Encapsulation
Ferruginous
Body Forms
Disrupted
Membranes
Easier Access for
Carcinogens
Inhibition of
Reductases
Carcinoma
Destruction of Normal
Mesothelial Cells
Mesothelioma
Carcinogen
Transport
Figure I.
-------
VO
Proline
Proline + Amino Acids
I nhalation of Asbestos
Increased Glycolysls
Release of a
Flbrogenic Factor
a-Ketoglutaric
Acid
Ri bo so ma! Bound
Protocollagen
*-
.A
Protocollagen
Hydroxylase
\
t
^Collagen ^Fibrosis
Figure 2.
-------
agent to critical tissues on the highly active surface of an asbestos fiber.
Also in Figure 1, the leaching of magnesium ions from the asbestos surface
is thought to interfer with solubility and ionic distribution of calcium. One
manifestation of a disturbance in calcium metabolism is the formation of pleural
plaques. Another manifestation is the induction of an orthodox to aggregate
transition (0 to A Transition) of mitochondria causing destruction of normal
mesothelial cells. Surviving abnormal mesothelial cells could grow in an un-
controlled environment according to the bioenergetics and tumor growth theory
described by Racker.3
Thus, a successful chemical treatment to detoxify asbestos depends on
three principles.
1. Silicate binding sites must be masked by an agent that remains in place
under physiological conditions.
2. Leachable ions such as magnesium must be removed.
3. The desirable physical attributes of asbestos such as strength, bulk
density, surface area, magnetic properties, flow characteristics, heat,
and chemical resistance must be essentially unchanged.
As an initial approach and assuming that the formation of a ferruginous
body is an attempt to detoxify the absorbed asbestos, a proprietary process has
been developed which prepares a highly saturated synthetic ferruginous body. The
process involving iron uses readily^ available, relatively inexpensive raw mater-
ials, and chemical compositions of treated asbestos have been prepared using
chrysotile, amosite, crocidolite, and anthophyllite. The treatment process
has also been extended to produce chemical compositions of asbestos containing
cobalt, manganese, chromium, aluminum, and copper.
Treated samples of amosite and chrysotile were tested for cytotoxicity
using human lung macrophage cells in tissue cultures according to the procedure
recommended by Wade, et al.1*
Figure 3 is an example of the results using a UICC chrysotile B. In the test,
cell cultures are allowed to grow for a 24-hr pre-exposure period. The cultures
are exposed to the material under test for 48 hours. The media and most of the
asbestos are removed, and the cells are cultured using fresh media for an addi-
tional 24 hours. Viable cells are counted at 24-hr intervals during the test,
and five fields are counted for each culture. The upper curve shows the average
number of viable cells in the controls, the next curve shows the average number
of viable cells in cultures exposed to a treated UICC chrysotile B, and the bot-
tom curve shows the average number of viable cells in cultures exposed to un-
treated UICC chrysotile B. The amount of asbestos in this series of tests was
100 micrograms/ml. Similar, but less dramatic results were obtained in tests
using a treated amosite. From these results, the chemical treatment of asbestos
decreases the cytotoxicity of the asbestos fiber to human lung macrophage cells.
493
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1000
Q_
o
CO
o
500
CO
C-4 CONTROL
TREATED MATERIAL
UNTREATED
•24
24
48
72
INTRODUCTION
OF MATERIAL
(START OF EXPOSURE)
TIME
Figure 3. Biology: Initial data on cell viability — UICC chyrosotile B.
-------
Table I Is a summary of physical attributes and differences caused by the
treatment process. The magnetic rating decreases. This could be an improvement
in the asbestos for certain electrical applications, but in other tests involving
phenolic molding compositions, there is an increase in the preheating time.
The magnesium oxide content decreases, and this is a desirable effect of the
treatment. Color is dramatically changed. The disadvantage is that the
color change may be unacceptable in certain products. An advantage is that
the treated materials are readily identified. In cement formulations and
phenolic resins, the color change is not a problem. The viscosity of a spin-
ning solution containing AAA grade chrysotile decreases as a result of the
treatment. A large scale test on a production line is needed to evaluate the
impact of decreased viscosity on the quality of the textile produced. There
is a decrease in cement strength at a high level of treatment, but no changes
in cement strength were found at intermediate or low levels of treatment.
No changes in resin absorption, alkali resistance, acid resistance, and ther-
mal insulation properties were produced as a result of treatment. The fiber mill-
ing and processing is changed to a wet process. Cytotoxicity shows a substantial
decrease. The drainage rates of cement formulations decrease with increasing
levels of treatment. A decrease in drainage rate may require changes in the
drying, curing, and forming of asbestos cement products. In working with sev-
eral grades of asbestos from AAA to 7RF99, a wet process tends to increase the
surface area and to decrease the bulk density of longer fiber materials, but
these changes may be attenuated by controlling contact time in the wet process
and by more efficient dewatering. The treated asbestos materials compare favor-
ably with the desirable attributes of raw or untreated asbestos.
In summary, initial biological data show that chemical treatment of asbestos
to form a saturated synthetic ferruginous body decreases the cytotoxicity of asbes-
tos to human lung macrophage cells. Physical test data indicate that desirable
attributes of the fibers are retained. If additional in vitro and in vivo bio-
logical tests are successful in demonstrating a decrease in toxicity as a re-
sult of the chemical treatment and the performance of treated material is ac-
ceptable in products, this would allow treated fibers to serve as substitutes
for asbestos in appropriate applications.
REFERENCES
1. Flowers, E.S.: Relationship Between Exposure to Asbestos, Collagen Forma-
tion, Ferruginous Bodies, and Carcinoma, Amer. Ind. Hyg. Assoe. J., 729-
742, 1974.
2. Heppleston, A.G.: Fibrogenic Action of Silica, Brit. Med. Bull. 25, 282-
287, 1969.
3. Racker, E.: Bioenergetics and the Problem of Tumor Growth, Amer. Sci. 60
(1), 56-63, 1972.
4. Wade, M.J., Lipkin, L.E., and Frank, A.L.: Studies of in vitro Asbestos-
Cell Interaction, J. Envir, Path, and Tox., 2, 1029-1039, 1979.
495
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TABLE 1. DIFFERENCES CAUSED BY TREATMENT
JS
VO
Magnetic rating
Magnesium oxide content
Color
Viscosity of spinning solution
Resin absorption
Cement strength
Alkali resistance
Acid resistance
Thermal insulation
Fiber processing
Drainage rate of cement formulation
Biological effect (cytotoxicity)
Decrease
Decrease
Yellow, brown, blue, green
Decrease
No change
No change except at high level of treatment
No change
No change
No change
Wet process
Decreases with increasing level of treatment
Substantial decrease
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DISCUSSION ON CHEMICAL DETOXIFICATION OF ASBESTOS FIBERS
QUESTION (Mr. Taitenann): I am from Raybestos-Manhattan. I would like to
raise the question about the use of the wet process. Could you
describe the wet process to us, please?
ANSWER (Dr. Flowers): This may sound like blasphemy or a sacrilegious
treatment of the asbestos fiber, but essentially, I make a slurry
containing about 5 percent by weight of asbestos fiber, which
would be about 95 percent by weight of water. There are two steps
in addition to the treatment chemicals. The material is filtered
initially and then put in a press. I have been using my wine press
to dewater the asbestos. Then it can either be shipped as a wet
cake containing about 30 percent moisture, or it can be dried and
then fiberized.
I neglected to mention that in the laboratory scale operation,
there are real problems with the wet process in terms of maintain-
ing the desirable surface or bulk density of the material. I
found, however, that in producing, say, a few grams of material
I can control the contact time and the wet process. I can also
filter the material fairly quickly and attenuate the possible ad-
verse effects on enhancing or opening up the surface, which would
make it unuseable in certain processes.
I can produce asbestos that is fairly equivalent in surface area
by nitrogen permeability and such, but when I try to go to several
pounds, tens of pounds, or hundreds of pounds, I have found that
I just cannot scale up my laboratory to a reaction tank for this
system.
So the wet process may be a problem and requires a lot more work.
QUESTION (Mr. Taitenann): One other question. You referred to viscosity
in the spinning operation. What type of operation are you
referring to there?
ANSWER (Dr. Flowers): Well, I am not very knowledgeable about textiles in
the production of fibers, but Dr. Kunsey of the Ontario Research
Foundation did the evaluation of the spinning property, and he
said the viscosity changes, and to really know what this means
you have to produce enough sample to put it in a production line
and see what effect it has on that particular characteristic.
REMARK (Mr. Wright): I am from the Steel Workers Union.
Let me just make one historical comment. Let me first say that
I think your research is very interesting, but I want to, perhaps,
inject a note of caution about how readily it ought to be accepted.
First, I think that even if everything you say pans out, there are
questions about the stability of the coatings in the environment*
497
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and there are also, I think, some questions about the toxicity of
various coating materials, especially things like manganese and
possibly aluminum and chromium.
But let me make the historical comment, which is that back in the
thirties, there was a lot of excitement about the idea that
aluminum oxide therapy would be effective in protecting miners
from silicosis. The idea was that if one went into the mines and
then came out at the end of the day and breathed aluminum oxide
fumes or dust for some period of time, the aluminum oxide would
naturally coat silica particles in the lungs and thereby protect
the miner. The therapy was based on two things: the first was
some preliminary biochemical theories about the way silica dust
acted in the lungs, the idea that one could encapsulate whatever
the problem was by the aluminum oxide; the second was based on
some very preliminary animal studies. Those studies were dis-
credited within, I think, about 10 years, but nevertheless, based
on the very preliminary work, the underground mining industry and
a lot of foundries adopted this procedure. Many underground miners
and foundry workers spent the last half hour or 15 minutes of their
work day, depending on how it was done, breathing aluminum dust.
Some of those people may have long-term lung disease from that
therapy, which was proven not to protect them against silicosis.
That has been very well documented. As a result, the method was
scientifically discredited by the late 1950s. In 1978 we dis-
covered several mines in Northern Canada that were still using the
therapy and we stopped it very quickly. And there may be more
people out there who are still using it.
The point I am trying to make is that it is very easy to jump to
conclusions about the effectiveness of a particular detoxification
process, and there may be some who would do that as an alternative
to cleaning up the work place. I am not saying this to discourage
your research. I am saying it to discourage the too-rapid adoption
of a method that is not yet proven. And I think if I were ques-
tioned by one of the workers who I represent, I certainly would not,
at this point, say that treated asbestos should be considered any
safer than untreated asbestos. Maybe with more research, but I
think that will take a lot of additional work.
REMARK (Dr. Flowers): I agree with just about everything you said, although
I cannot confirm your experience regarding aluminum oxide as
therapy in prevention of silicosis. But I tried to be fairly
careful in how I characterized the results of our initial biolog-
ical tests. In my summary, I indicated that it is successful in
some rather extensive additional biological in vitro and in vivo
tests.
498
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Also, if through process engineering and economics, we find that
the material retains the desirable physical properties and will
work in various industrial processes, then it could be accepted
as a process for chemical treatment and detoxification of asbestos.
From an economic and biological point of view I think that iron
oxide, or various forms of it, is the only real treatment that
will be acceptable.
There was somewhat of a chemical academic Interest to extend the
treatment to chromium or other transition metals to show that this
is a general reaction across the transition metal group and also
with amphoteric materials.
I agree that a lot more work needs to be done. In our communica-
tions with the EPA, they say that the tests, particularly the
biological data, will have to be very persuasive for them to
accept such a substitute. And that is not only for our material,
but also for all the 60 or so materials that have been proposed
as substitutes here over the last few days.
REMARK (Mr. Wright): I would like to make one final comment, not about what
you presented, which I have no quarrel with, but about iron oxide.
There are some questions about iron oxide itself being a cocarcinogen
based on two things. One is some work that Saffiotti and others did,
exposing, I think, Syrian golden hamsters simultaneously to iron oxide,
and a carcinogen. This showed a. greater response when the iron oxide
was administered along with the carcinogen than when the carcinogen
was administered alone, even though iron oxide alone did not give any
increased carcinogenic response.
Also there have been some epidemiologic studies in gray iron and
steel foundries indicating an increased risk of cancer in those
work places. We do not know what that is caused by, but one hypo-
thesis is iron oxide, so you have to be careful.
REMARK (Dr. Flowers): Iron oxides are a normal waste product of oxidated
metabolism in cells. The ferric hydroxide is sometimes viewed as
the brown gelatinous amorphous material floating around in the
cells, so essentially, the iron is something like that amorphous
gelatinous material. However, from our X-ray defraction data, we
have prepared a highly ordered form of this material, using the
asbestos surface as template for its precipitation and formation.
QUESTION (Dr. Fatel): I am from the New Jersey State Department of Health.
I have three questions. One is what happens in your lung cell
tests beyond 72 hours after treatment. The other is what happens
to the acoustic properties of asbestos. Finally, is this process
useful only in the manufacturing aspect of asbestos or could it be
used after the product has already been manufactured, for example,
in school ceilings? Can you treat the manufactured product so
that it will penetrate further and not only remain on the surface?
499
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ANSWER (Dr. Flowers): We do not know what happens after 72 hours because
the test protocol stops after 72 hours. This is a short-term
assay to evaluate the initial biological response.
We do not look at acoustic properties. Ontario Research can make
test panels and measure the acoustic properties, but that was one
test we did not look at.
The process is essentially a technique for contacting the asbestos
surface with a solution of treatment chemicals. Depending on your
degree of imagination, you could contact the exposed asbestos at
the mine with the treatment chemical. I claim that you could
develop devices for contacting asbestos wherever you find it, in-
cluding those asbestos fibers which are already present in the
lungs of people who have been exposed, thereby providing a syn-
thetic process for deriving a synthetic ferruginous body from an
exogenous source of ferric salts.
REMARK (Dr. Cooper): 1 am from Berkeley. I wanted to make a comment on the
remarks of the Steel Workers' representative. 1 certainly agree
with him and with Dr. Flowers that something like this has to be
studied and approached very cautiously and certainly is not a sub-
stitute for industrial hygiene.
I do not think that the analogy with aluminum and silicosis is
quite applicable here. There is very good biologic evidence that
aluminum and iron do modify the fibrogenic potential of silica;
that has not been, shall we say, discredited. The thing that has
been discredited is the inappropriate application of aluminum and
iron to the prevention of silicosis. Substituting the addition of
inhaled aluminum powder for adequate dust control has been justi-
fiably discredited. Since it was clearly impossible to coat with
aluminum the quartz particles that resulted from drilling a hole
in a hard-rock mine, the effort was made to coat them after they
got into the body. Although I think it is a difficult path that
has to be followed to establish these things, I do not think that
that analogy should be used to discredit this type of approach.
QUESTION (Mr. Wilkin): I am with Dresser Industry. The three criteria that
you provide for detoxifying the fibers are: removing the mag-
nesium oxide surface, ensuring the surface is stable to alkaline
conditions, and maintaining the same strength and flow properties
of the resultant material. Do you have any comments on the other
methods of doing this, such as the acid leaching and organosilane
or sodium silicate treatments that are currently patented?
ANSWER (Dr. Flowers): I was very interested in the Dow patents, for example,
involving the molybdate and tungstate treatment. They used a
Grade 7 chrysotile and showed that hemolytic activity could be de-
creased up to 100 percent by treating the surface with the molybdate
* and the tungstates. They used a wet process. I think they
500
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also removed some of the brucite or the magnesium oxide associated
with the surface. The metallic tungstate and molybdate salts are
alkaline resistant, so I think it does not violate the three prin-
ciples that I have enunciated.
The heat treatment of asbestos actually drives off hydroxide by
hydroxide reaction or oxidation with oxygen. This gets rid of
hydroxyl groups. I think that when you hydrate or rehydrate sili-
cate bonds you may have some problems once they are deposited in a
physiological system.
One other treatment used is the removal of magnesium oxides and
other metals by moderately strong acid treatment of the surface.
According to the paper presented in May, by Marcelle Cahette, at the
Fourth International Conference on Asbestos in Italy, they have suc-
cessfully demonstrated decreased cytotoxicity and decreased release
of enzymes from membranes and also decreased hemolytic action of the
chrysotile asbestos, which had been subjected to the moderate acid
treatment.
So, yes, there are other approaches. My approach was to mimic what
I consider to be a detoxification attempt by the body and to make
a synthetic ferruginous body.
QUESTION (Mr. Wilkin): Would your studies also include the possibilities of
detoxification by the reaction of the surface with an organosilane
to make the surface hydrophobia?
ANSWER (Dr. Flowers): I cannot comment on that one way or the other, but I
really have not given any thought to that particular process.
REMARK (Mr. Wilkin): There are a. few applications for asbestos that would
probably best be served by a hydrophobic coating rather than a
hydrophilic coating.
REMARK (Dr. Flowers): I do not want to make my process mutually exclusive
of other processes. I think there is probably room in the sub-
stitute field for many products.
REMARK (Dr. Gross): I am with the Industrial Health Foundation. If phago-
cytosis to these treated fibers does take place, then we are up
against another facet that contradicts the present theory of the
pathogenicity of asbestos, namely, the theory that incomplete
phagocytosis of the asbestos fiber causes leakage of intracellular
enzymes into the surrounding medium and, consequently, into the
surrounding tissues. The leakage of these intracellular enzymes
would then cause tissue damage and, ultimately cancer.
If your demonstrated lack of cytotoxicity by the treated asbestos
fiber takes place in spite of phagocytosis, then this theory falls
into the ash can, and we do not have a viable theory for the patho-
genicity of asbestos. Our concern for the substitutes for asbestos,
501
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like man-made vitreous fibers, also should be abated because this
concern is based on the theory that the geometry of the fiber in
great part is responsible for the pathogenicity of fibers.
It is agreed that the geometry of a fiber is responsible for the
fiber landing at the target site, but if this theory about leakage of
intracellular enzymes into incomplete phagocytosis is destroyed, then
we should not have any concern for the pathoeenicity of manmade fibers.
QUESTION (Dr. Bernstein):^ I think Dr. Gross's comments are well taken. I
would like to ask you, along the same lines, did you do size mea-
surements of your fibers, and if you did, did you do it before they
were treated and after they were treated, and what sizes were they?
ANSWER (Dr. Flowers): Yes, we have rather extensive data, both the light
microscope and the electronmicroscope data on the size distribution
of the fibers and the effect of treatment on size.
There is a slight increase in average diameter after treatment,
compared to before treatment.
QUESTION (Dr. "Bernstein): What were the figures?
ANSWER (Dr. Flowers): I do not have the figures with me.
QUESTION (Dr. Bernstein): What about the length? Did you look at length?
ANSWER (Dr. Flowers): No. I used Grades Triple A chrysotile, Grades 4 and 5
chrysotile, Grade 7 type purity, Grade 7 RF 99, and these go from
extremely long materials to extremely short fine fibers.
REMARK (Dr. Bernstein): Well, I think it is important to point out that the
effects you have shown could be explained by either a change in
diameter, an increase in diameter, perhaps, or a decrease in
diameter and/or length. And until that is straightened out and
put on the record, it is really unfair to interpret the results.
QUESTION (Dr. Flowers): What percentage change would be significant, in
your opinion?
ANSWER (Dr. Bernstein): I could not venture a guess until I saw your results
and I do not know if I could venture a guess after that until I
have seen the experiment.
REMARK (Dr. Flowers): There is less than about a 5 percent change in diam-
eter and no change in length.
We mainly took pictures sufficient to count the cells, but not to
evaluate whether phagocytosis was going on. So that is an omission.
502
-------
REMARK
REMARK
In the protocol that we followed, we primarily were interested in
seeing if we could demonstrate a decrease in cytotoxicity and that
was the one issue we looked at. We did not look at some of these
other issues, which now seem to be more important, or assuming more
importance.
(Dr. Bernstein): Relating to Dr. Gross's comments, I think if you can
demonstrate that the phagocytes are ignoring your coated fiber
(and you probably could do that using the methods that we saw from
the Brookhaven National Laboratory), you might'be able to support
your findings a lot better.
(Dr. Flowers): We do not make any claims that this is the only test
that we are going to run. As a matter of fact, this afternoon
I am going to talk about criteria for acceptable test protocol for
evaluating proposed substitutes. This was based on an unofficial
request to EPA under Section 4(g) of TSCA, as a petition for accept-
able test protocols for evaluating and, subsequently, if successful,
registering a product for use. We do plan more extensive in vitro
and in vivo tests.
503
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HEALTH CONSIDERATIONS IN THE PERLITE INDUSTRY
by
W. Clark Cooper, M.D.
2150 Shattuck Avenue, Suite 401
Berkeley, California
ABSTRACT
Commercial perlite is a naturally occurring glass of volcanic origin which,
when heated, expands to form a product of low density, high surface area, and
low thermal conductivity. Expanded perlite is used in thermal insulation as
a filter aid, as an inert carrier and filler, and as a soil conditioner. Per-
lite is a noncrystalline silicate. Most ores and products contain less than
1 percent quartz or cristobalite, although there are commercial deposits with
as much as 5 percent quartz.
Studies in animals reported in 1953 showed no evidence of pulmonary fibrosis.
Nevertheless, most major producers and processors provide periodic chest films.
A review of films in 240 perlite workers which was reported in 1975 showed no
evidence of pneumoconiosis associated with perlite exposures: however, only 28
of those studied had been in the industry for 15 years and only 7 for 20 years.
A recent updated review, which involved 43 men with 15 or more years in the in-
dustry and 18 with 20 or more years, again showed no evidence of perlite-related
pneumoconiosis. Pulmonary function in. 117 perlite workers was studied in 1975;
there was no decrement in forced vital capacity. There was slight, but not sta-
tistically significant, reduction in average forced expiratory volume. An up-
dated review of pulmonary function is now underway; preliminary findings do not
indicate a significant effect from perlite. Current recommendations are that
perlite be regarded as a nuisance dust except in products with 1 percent or more
crystalline silica.
INTRODUCTION
Perlite is a naturally occuring noncrystalline silicate of volcanic origin
which expands when heated to form a product of low density, high surface area,
and low thermal conductivity. It is not fibrous. The principal end uses of ex-
panded perlite are filter aids, construction aggregates, horticultural aggre-
gates, acoustical tile and insulation products. It can be regarded as an asbes-
tos substitute in only a limited sense, as in some specialized insulation mater-
ials. The principle competitive commodities are vermiculite, pumice, slag,
diatomite and expanded clay and shale.
505
-------
The perlite industry has a comparatively short history, the commercial
possibilities of the material not having been recognized until after World War
II. Production in the United States'began in 1946; there are now 13 mines in
6 western states, with New Mexico accounting for 88 percent of the total out-
put in 1979. In that year processed perlite sold or used in the United States
totalled 650,000 tons.
Mining of perlite is by open pit. Although expansion is carried out by
some producers near the mining sites, it is a common practice to ship the crude
ores to expanding facilities near points of distribution.
Expansion is carried out by injecting finely divided crude ore into fur-
naces fired by gas or oil, where temperatures are maintained in the range of
1400 to 2000°F (760-1100°C). The 2 to 5 percent combined water in the crude
ore causes the particles to "pop" or expand, producing a product with a bulk
weight of 3 to 12 pounds per cubic foot, compared to a bulk weight of 65 to
75 pounds per cubic foot for crushed and sized crude perlite ore. After ex-
panding, the particles are classified by size prior to shipment or use.
DESCRIPTION OF PRODUCT
Perlite ores and expanded perlite are largely aluminum silicate, in a
noncrystalline, nonfibrous form. Some perlite ores contain small amounts of
crystalline silica; i.e., quartz, but most do not. For example, analyses of
se/eral samples by the Bureau of Mines in 1956 showed quartz concentrations
ranging from less than 1 percent to 3.0 percent. Other analyses in 1971 by
McCrone Associates showed quartz concentrations ranging from under 0.5 per-
cent to 5.8 percent in ores, and from 0.5 percent to 5.2 percent in expanded
perlite. In 1979, five ores and resulting products were analyzed for the
Perlite Institute. Quartz and cristobalite concentrations were measured in
the ores and products, and in total airborne dust and respirable dust. In
most, quartz was below detectable range; the highest concentration in respirable
dust, from one product, was 1.7 percent. In no case did cristobalite exceed
1 percent.
The potential for dust exposures in the perlite industry are those of
any operation in which there is open pit mining, crushing, screening, and
loading of ores, and the subsequent production and handling of a finely par-
ticulate product. Those who use expanded perlite in the manufacture of various
end products are of course also subject to potential dust exposures.
There are no published figures on airborne concentrations of dust in the
perlite industry, but available unpublished data indicate that nuisance dust
levels are easily exceeded during some operations, such as bagging or cleanup,
unless precautions are taken.
BIOLOGIC EFFECTS
In 1953 Vorwald1 et al reported no evidence of fibrosis following intra-
tracheal injection of 0.5 percent of a 5 percent suspension weekly in guinea
pigs for 3 weeks. Nine products were tested. One product was tested by inha-
lation in guinea pigs and rats over a period of 18 months with an average
506
-------
dosage of 590 mppcf (6.4 mg/ft3 or 226 mg/m3). No significant pulmonary reac-
tion was observed. Schepers2 subsequently reported that the inhalation of high
concentrations of perlite appeared to stimulate the progression of experimental
tuberculosis in guinea pigs. Infections, however, became arrested several
months after exposures stopped. The exposures were extremely high, being main-
tained for 8 hours a day, 5-1/2 days a week for 6 months at average concentra-
tions of 582 mppcf with 50 percent to 80 percent in a respirable size range.
On a weight basis, exposures averaged 8.03 mg/ft3 or 284 mg/m3.
STUDIES IN EXPOSED POPULATIONS
Advisors to the perlite industry in 1953 recommended that perlite producers
and expanders maintain medical surveillance of exposed workers and not permit
unrestricted dust exposures. These programs have made available files of chest
radiographs which in recent years have become useful to determine if there has
been any evidence of pneumoconiosis.
The first published review,3 supported by a contract from the Perlite
Institute, Inc., involved films taken through 1974 (Table 1). Records were
obtained on 100 men identified as working in perlite mining operations and
185 in expanding operations. The latter offered opportunities for exposure
either to crude or expanded perlite. Films were obtained on 240 individuals.
One individual found to have simple pneumoconiosis and one with complicated
pneumoconiosis had formerly been employed in the diatomaceous earth industry,
one for 13 years, the other for 24 years. Because only 28 of those studied
had been employed for 15 or more years in perlite, and only 7 for 20 or more
years, the results were regarded as preliminary. It was concluded that con-
tinued surveillance was 'essential to make sure that there are no effects with
more prolonged exposures. Studies of pulmonary function of individuals with
relatively long exposures were recommended.
An updated radiographic review was carried out in 19791* (Table 2), in
which 6 of the 10 plants which participated in the 1974 study took part.
These six plants had furnished over 90 percent of those included in the first
study. The study was limited to men with 5 or more years in the industry.
There were 130 individuals whose films were reviewed; 93 of these had been
included in the 1974 study. Of the participants, 46 were from plants which
mined and shipped crude perlite; 62 were from an operation where perlite was
mined and also expanded, while the remaining 22 were from plants where crude
perlite was expanded. Table 2 summarizes the film interpretations, based on
readings by radiologists certified as 8 readers. Table 3 provides details on
the four individuals interpreted as positive for pneumoconiosis. There still
appears no pattern of disease associated with working with perlite.
PULMONARY FUNCTION
In June 1975 pulmonary ventilatory function was studied in 117 men em-
ployed in three plants engaged in the mining or processing of perlite.5 Forced
vital capacity and forced expiratory volumes in one-second were determined
using a 9-liter Collins spirometer and a model II Jones Pulmonor. A detailed
summary of the findings was reported in November 1976. Forced vital capacity
measurements did not show reductions that correlated with length of exposure.
507
-------
TABLE 1. FILM INTERPRETATIONS IN PERLITE WORKERS
(1974 Survey)
Years in the
Per lite Industry
0- 4
5- 9
10-14
15-19
20-24
Total
No. of men
with films
106
52
54
21
7
240
Changes consistent with
Negative
105
50
52b
18
6
231
Doubtful
1
1
1
3d
le
pneumoconiosis
Positive
0
la
lc
0
0
2
a • '
Complicated diatomite pneumoconiosis (24 years in DE).
One with residual of pneumonitis.
CSimple diatomite pneumoconiosis, exposure approximately 13 years.
One with exposure to diatomaceous earth.
6One with exposure to diatomaceous earth.
508
-------
TABLE 2. FILM INTERPRETATIONS RELATED TO YEARS IN THE
PERLITE INDUSTRY (1979 Survey)
Changes consistent with pneumoconiosis
Years
5- 9
10-14
15-19
20-24
25-29
Total
No.
54
33
25
13
5
130
Negative
(0/-0/0)
49
28
21
11
4
113
Doubtful
0/1 1/0
1 2
2 3
1 1
2 -
_ •>
6 7
Positive
1/1 2/2 3/3
1
-
2
-
-
3
- la
- -
- -
-
- -
- 1
HPresent in pre-employment film 1966, interpreted as
pleural changes at that time.
TABLE 3. FILMS INTERPRETED AS POSITIVE (1/1 or greater)
No. Classification Age Years Jobs Comments
1 1/1 48 5 truck driver no previous film
2 1/1 54 17 bulldozer op. no change since
truck driver 1967
3 1/1 48 18 mobile eq. op. slight change
maint. mech. since 1960
4 3/3C 61 9 general worker called pleural
(6 years) changes in 1966
grizzly op. and 1974. Term:
maint. mech. 1975; died 1976
(no autopsy)
509
-------
There were slight reductions in FEV]. and in the FEVi/FVC ratio. Although
these could not be entirely explained by cigarette smoking and were associated
with number of years in the perlite industry, the reductions were not statis-
tically significant beyond the 0.1 percent level.
The major producers of perlite continue to maintain a program of periodic
chest films and since 1975 have provided annual testing of pulmonary ventilatory
function. An analysis of later pulmonary function results obtained during 1977,
1978, and 1979 is now underway; preliminary indications'are that there is no
evidence of a systematic reduction of function associated with perlite exposure.
SUMMARY AND CONCLUSIONS
There is no evidence to indicate that individuals engaged in the mining,
expansion, or use of perlite develop pneumoconiosis. Nevertheless, it is
recommended that there be strict adherence to nuisance dust levels, assurance
that quartz levels are never excessive, periodic medical surveillance, and
retention of records and chest films for periodic reevaluation.
REFERENCES
1. Vorwald, A. J. Perlite Dust Investigation, Final Report: The effect
of inhaled perlite dust upon the lungs of normal animals, to the Perlite
Institute by the Saranac Laboratory of the Trudeau Foundation, Saranac
Lake, New York. March 12, 1953 (Perlite Institute, New York, 1953).
2. Schepers, G. W. H. The biotoxicity of perlite: Report to the Perlite
Institute by the Saranac Laboratory, March 19, 1955 (Perlite Institute,
New York).
3. Cooper, W. C. Radiographic Survey of Perlite Workers. Journal of
Occupational Medicine 17:304-307, 1975.
4. Cooper, W. C. Review of Chest Radiograms of Perlite Workers, pre-
liminary report presented at 31st Annual Meeting of Perlite Institute,
Inc., April 22, 1980.
5. Cooper, W. C. Pulmonary Function in Perlite Workers. Journal of
Occupational Medicine, 18:723-729, 1976.
510
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DISCUSSION ON PERLITE
QUESTION (Dr. Langer): I am from Mt. Sinai.
Is the silica present in this material as discrete particulates or
does it have crystalline domains and are the surfaces a little bit
greater? In other words, if there is a 1 to 10 silica content, does
it mean 1 percent is discrete particles. Do you have more exposed
silica surface?
ANSWER (Dr. Cooper): I do not know and I am not sure that that is known.
I think that it is more or less a contaminant associated with the
ore body, but I do not know.
511
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REVIEW OF THE HEALTH EFFECTS OF MICAS
by
Mr. Ilmar Lusis
Manager Industrial Hygiene
Martin Marietta Corporation
6801 Rockledge Drive
Bethesda, Maryland 20034
ABSTRACT
Available literature on locations, characteristics and uses of micas is briefly
discussed.
Available world literature on bioactivity and pneumoconiosis attributed to
micas is reviewed. An attempt is made to separate cause-effect relationships
according to the type of mica causing the exposure or used in the experiment.
Insufficient data were found to make the distinction. Electron microscope
photographs of micas from various sources are enclosed.
According to Petkof in his chapter on mica in the compendium "Industrial
Minerals and Rocks" mica or micas are predominately potassium, aluminum silicates
with varying amounts of magnesium, iron, lithium and some other trace metals.1
These minerals have layered lattice-type internal structure, with tetrahedral
grouping of oxygen atoms surrounding silicon atoms or aluminum atoms. Tetra-
hedral groupings result in pseudohexagonal network within a plane. The double
or mirror image network is superimposed on the "peak" side of the tetrahedron
and the two layers are joined by hydroxyl groups or metallic ions such as
aluminum, magnesium, or lithium. These double layered structures are joined
by potassium atoms. The potassium atom locations constitute the cleavage
plane of mica. The American Conference of Government Industrial Hygienists
defines micas as "nonfibrous silicate occurring in plate form" including nine
different species.2
Distribution of micas is probably worldwide. It is found both in metamorphic
and igneous rock. The decomposition of such rock produces sand and clay and
introduces finely ground mica into our environment where it is naturally distri-
buted by wind and water the same way as any other mineral. In relation to man
this condition must have existed throughout the history of mankind.
However, let us get back to science. When we consider the idealized chemi-
cal structures of the complete crystal, it becomes obvious that muscovite and
phlogopite appear structurally more uniform than biotite. (Fig. T) These two
513
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MARTIN MARIETTA CORPORATION
Idealized Mica Formulas
MUSCOVITE - K2 AI4 [Si6AL2020] [OH,F)4
COLORLESS
PHLOGOPITE - K2 (Mg, Fe+2)6 [Si6 AI2 020] [OH.F]4
COLORLESS
TO BROWN
BIOTITE - K2 (Mg. Fe+2)6.4 (Fe+3, Al, Ti)0.2 [Si6.5 At 2.31 OQ-2)
BLACK.
BROWN- (OH. F)4 2
GREEN 4-Z
Figure 1.
-------
are the predominant commercially used micas. Muscovite probably accounts for
about 90 percent of the mica used in the world. This became quite obvious
during the literature search.
This approximate schematic does not lay claim to perfection; (Fig. 2) it
does depict approximate possible paths of conversion from one mineral to another
over a long period of time. Other paths may be entirely possible because there
is one concept in geology that is absolutely true—for every rule and general-
ization there are numerous exceptions.
I would like to call your attention to the term "pegmatite." It really
refers to the structure and not to the composition of this particular granite
variety. Returning to the economically important micas, namely muscovite and
phlogopite, it is important to note that almost all of the muscovite recovered
in the United States is a co-product or by-product in quartz, feldspar, kaolin
and perhaps garnet recoveries, or vice versa. Consequently the impurities of
that nature could be expected in the commercial grade micas. Sericite, which
is a hydrothermal disintegration or weathering process end product or possibly
a direct result of metamorphosis, contains considerable amounts of free silica.
Even though on occasion cited in the literature as a mica, it should be con-
sidered as part of the clay family, at least for commodity purposes. One
author claims that pure mica dust in the lung is less fibrogenic than a mixture
of mica and free silica.4
The main commercial products of micas are sheet mica, scrap or flake mica
and ground mica. Sheet mica, both muscovite and phlogopite, is found visually
and hand-picked from the mined matrix rock. The sheets are hand separated in
a way similar to separating pages from a wet book; the same material can be
sold also in "block form." The value of sheet mica depends on size, clarity,
color and in some occasions on the dielectric properties. In ground micas,
depending on the end use, other properties may be important.
The leading manufacturers of sheet mica (splittings and block) in the
world are India, Brazil and Malagasy. Sheet mica is used primarily in the
manufacture of electrical appliances, vacuum tubes, electronics and capacitors.
From a physiological and perhaps health standpoint, the scrap, ground and flake
mica is more significant. (Fig. 3) The United States is still the leader in
scrap, ground and flake mica production. Looking at the 1977 data reported by
U.S. Bureau of Mines, one can see the distribution of end-products according
to standard industrial classification codes.5
The following map (Fig. 4) shows the counties in the United States in which
mica is produced for commercial purposes. The consuming states are again not
particularly widely distributed. Over 80 percent of U.S. block mica and film
used in fabrication is consumed in New York, Pennsylvania and Virginia. North
Carolina, Massachusetts, and Ohio are the other consuming states.
Ground mica in 1979 was produced in Alabama, New Hampshire, New Mexico,
North Carolina, Pennsylvania, South Carolina and South Dako'ta. The same states
also produced mica flakes. Mica flake was also produced in Connecticut and
Georgia. When export and import data are considered, United States exports and
imports about 6 million pounds of mica each year. For comparative purposes,
515
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MARTIN MARIETTA CORPORATION
Ol
PEGMATITE (IGNEOUS OR MET AMORPHOUS
I (QUARTZ, FELDSPAR MICAS) ^DEPOSITS)
I • i
ILLITE 4-*'
**GLAUCONITE \
SERICITE
•CHLORITE
•CLAY
VARIETIES
Figure 2.
-------
MARTIN MARIETTA CORPORATION
Mica (Scrap and Flake)
SUPPLY-DEMAND RELATIONSHIPS 1977
THOUSAND SHORT TONS OF MICA
WORLD PRODUCTION
I
DELAMINATED
IMIHISMTIS
in
MOU
aim
nc
WORLD TOTAL
276E
KEY
( enure)
X STMBMB MOUSniM OASSRUTOI
» SOW MM
BUREAU OF MINES
U.S. DEPARTMENT OF THE INTERIOR
Figure 3.
-------
MARTIN MARIETTA CORPORATION
Mica Mining Counties (including Sericite) In U.S.A./Spring 1980
00
Figure 4.
-------
the total world production of micas in 1978 was 533 million pounds. In 1979
it dropped to 528 million pounds.6 These estimates do not include the pro-
duction of such countries as Rumania. U.S. consumption of sheet and scrap
or ground mica at the same time was 5.1 million pounds of sheet and 244 mil-
lion pounds of ground mica. The production of mica paper should be noted as
possible means of substituting sheet mica.
However, geology, geographic distribution and economic usefulness of
mica is not the title of this paper. In the search of the health effects of
micas, as the title of the paper would indicate, it is difficult to establish
a starting point. In 1933 in the Journal of Indusrial Hygiene, W. R. Jones
reported finding sericite in silicotic lungs and proposed the sericite crys-
tals as the causative factor in pulmonary silicosis. In May of 1934, A. Poli-
card from the University of Lyon in France reports on his animal experimenta-
tion involving finely ground "white mica dust," to which he subjects test
animals in substantial doses for four hours a day, sacrificing them after three,
five, sixteen and thirty days of exposure. He concludes that the lung changes
have occurred, namely that "the altered cells are grouped in plaques in the
alveoli. About them the pulmonary histocites gather, the aggregate forming
a sort of mica granuloma."7 His experimental evaluation techniques were lim-
ited to an optical microscope. The paper, unfortunately, does not state the
dust concentration to which the animals were subjected.
The next significant publication chronologically is the almost classic
study by Dreessen, Dallavale and others, entitled "Pneumoconiosis Among Mica
and Pegmatite Workers," also known as U.S. Public Health Bulletin No. 250.8
This study has served as a basis for threshold limit value determination of
mica dust in the United States. Some of the airborne dust concentrations
reported in the study were extremely high, such as kiln drying and manual bag-
ging of mica, averaging 116 million particles per cubic foot and crusher dust
ranging from 40 to 1,000 million particles per cubic foot. These values would
apply to mica mining and recovery. Wet mica grinding operations ranged between
3.1 million particles per cubic foot and 158 million particles per cubic foot
in the drying stage.
Mica fabricating, such as mica sheet trimming, splitting and punching
produced dust concentrations of only 3.2 million particles per cubic foot on
the average. Consequently, no pneumoconiosis cases were seen in that group
of workers. In mica grinders, symptoms of pneumoconiosis appeared between the
tenth and nineteenth year of employment. The disease symptoms resemble those
of silicosis. The symptoms were supported by x-ray diagnosis indicating gran-
ulomas and fibrosis of the pleura. The following figure taken from the bul-
letin dramatically portrays the time-concentration relationship of dusty trades
with respect to the development of pneumoconiosis. (Fig. 5) This figure rep-
resents the findings in 798 workers including the 57 mica workers exposed to
mixed dust and classified according to length of employment as well as the
average dust concentration. The graph deals with all pneumoconiosis cases.
After five years of employment, the number of workers in each grouping decreases
with the increase in years of employment. The percentage represents the chance
of finding pneumoconiosis. The 66 percent group consists only of six individuals
of which four had pneumoconiosis. Of interest is Appendix II in the study, pro-
duced by Dr. John W. Miller. He used some of the minerals encountered in the
519
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MARTIN MARIETTA CORPORATION
ro
o
RELATION OF AVERAGE DuST CONCENTRATION AND DURATION OT
OUST EXPOSURE TO THE PCI«CCNTACC OF WORKERS FOUND TO HAVC PNKUMO-
CONIOSIS.
Dreessen, W. C.» et al.3 p.50.
Figure 5.
-------
study to conduct an animal experiment with guinea pigs. He used finely ground
muscovite mica with a very small amount of quartz and feldspar present. He
found that mica produced an "inert reaction." The term "inert" he defines as
a condition when the dust remains practically unchanged in the tissue and does
not institute a proliferation reaction like the more soluble quartz. The micro-
scopic appearance of the muscovite dust used was described as "plates and
fibers."
The field work was conducted between 1937 and 1939. The study was pub-
lished in 1940. At that time it was standard practice to report airborne
dust concentrations in million particles per cubic foot. This dust counting
method had quite a few drawbacks as the assessment method for airborne dust con-
centration. In the 1979 American Conference of Governmental Industrial Hygien-
ists adopted a method to convert million particles per cubic foot to a mass
limit of milligrams per cubic meter. A good approximation is 6.37 million
particles per cubic foot as being equal to 1 milligram per cubic meter. The .
converted threshold limit value for a 40 hour workweek is, therefore, 3 mil-
ligrams per cubic meter for respirable size particles and 6 milligrams per
cubic meter for total airborne dust.9 Respirable dust particles are those
with aerodynamic diameter of less than five microns. It is interesting to
note that the British threshold limit value for mica is one milligram per
cubic meter for respirable size and ten milligrams per cubic meter for total
airborne dust.
The late 1940*s and early 1950's produced a series of large scale employee
surveys in American occupational medical literature. Vestal and others in
1943, reported a high incidence of tuberculosis upon clinical and x-ray exam-
inations of 1,021 men applying for work in the mica industries in North Carolina.
Even though there was no associated field investigation, Vestal's conclusions
indicate that dust and tuberculosis pathology among the workers previously
exposed to "pure mica" is more pronounced than among those exposed to other
minerals.10 This conclusion was later questioned because quartz was present
in all of the other minerals.11
Dr. Adelaide Ross Smith, working with data gathered by the New York State
Department of Labor, published a paper in 1952 on calcifications of the pleura
resulting from exposure to certain dusts.12 The paper which is based largely
on chest x-ray survey data conducted by the Division of Industrial Hygiene of
New York State Department of Labor, reports the following:
"A group of 302 men exposed to mica dust were employed by a concern engaged
in making mica insulators of various types. Mica is a complex silicate of po-
tassium, aluminum, magnesium, calcium and fluorine. A number of operations in
the plant were dusty, including the sawing, sanding and drumming of insulators.
None of the mica workers in this study showed pneumoconiosis though Dreessen
and others have found that mica dust is capable of causing this condition if
present in sufficient intensity." Unfortunately, this study does not mention
any concentrations to which these workers were exposed. The length of employ-
ment is mentioned in two clinical cases described. The report does state that
lung calcifications were found in five of the 302 workers reviewed. As these
were x-ray findings they do not deal with the origin of calcifications.
521
-------
Jones' hypothesis of 1933 found an echo in 1947. King and others asso-
ciated with the British Postgraduate Medical School in London, investigated
South Wales sericite and illite due to their association with coal mining.
Two different sericite samples from different geographic locations were used
in an insufflation experiment with rats. The dust samples were split and half
of the dust aliquot was treated with hydrochloric acid and then neutralized
before administration to test animals. The experiment ran for two months.
Acid treated dust released silicilic acid in the lung with considerable ease,
producing fibrous nodules in the test animals. The untreated half of the dust
produced only fibrous phagocytosis.13 Please remember that sericite and shale
both contain substantial amounts of free silica.
In 1953 and 1954 two articles appeared in literature describing medical
examinations of 329 mica miners from Bihar, India and of dust exposures to
61 mica factory workers in the same region; they processed crude mica.11* The
exposure data on mica miners resembles those described by Dreessen in his
North Carolina survey. Mica processing and grinding exposures range from 44
to 300 million particles per cubic foot with an average of 135 million particles
per cubic foot. The mica was muscovite, which contained less than 1% of free
silica. The environmental, as well as the previous work history, was not
given. The point was made that very few of the examined workers had been
working with mica for more than 5 years. Granulomas, found in the chest x-rays,
were not beyond "ground glass II" reading. Nodular or conglomerate fibrosis
was not observed. ^
The 1960's produced more research in physiology and pathology of the lung
in the dusty trades. In 1966, two Rumanians - Tripsa and Rotaru - published
an article entitled "Experimental Studies in Pneumoconiosis Induced by Mica
Dust."16 They introduced intratracheally into rats a one-time dose of 50 mil-
ligrams of sized mica suspended in a saline solution. They concluded that
small mica particles below 6 microns in size travel to the hiliary lymph nodes,
whereas the 20 to 25 micron particles remain lodged and display a higher patho-
genicity. They speculate that this particular observation may depend on mech-
anical damage during the injection and irritative action, and therefore it
might not be correct.
In 1962, Vorwald and others published a report on an autopsy case of a
rubber worker who during 33 years of employment was allegedly exposed for 21
years to "soapstone" dusting powder. The autopsy lung specimen contained
needle like crystals. The presence of both soapstone (fibrous talc) and bio-
tite was determined by x-ray diffraction. The diagnosis was "fibrogenic
pneumoconiosis induced by mica."17 The point in this case is perhaps the lack
of recognition for total combined impact, not only the mica and the talc but
all the other air contaminants which would be found in a rubber goods factory
in the 1940's and 1950's.
In 1968, Lewis J. Cralley and others published an article entitled "Source
and Identification of Respirable Fibers."1® In it they discuss the autopsy
survey statistics of several authors indicating presence of fibrous bodies in
the lungs of city dwellers. Four to six percent of those occupationally non-
separated autopsy cases described in seven studies showed "numerous fibrous
bodies." Cralley and others concluded that this finding was not a chance event.
522
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The implication was that fibers are present in the lungs of city dwellers in
quantity.
They further included a table of minerals with "fibrous-like structure"
taken from the text by Deer, Howie and Zussman. This test was published in
1966. In it, sheet silicates, specifically the mica group (muscovite) are
classified as having fibrous-like structure. With regard to the mica group,
this may be an imprecise statement. Structurally, true fibers are not found
in micas, except as impurities. As you will see later, the fine particulates
associated with mica are bladed, play or lamellar in appearance.19
In 1968, Mihajlov and Berova (in Bulgaria) published a paper which
describes the study of occupationally caused lesions associated with the pro-
duction of asbestos and mica.20 As only an abstract was available at the time
of writing this paper, the reported role of mica in occupational dermatoses
could not be determined.
In 1969, Landwehr and Bruckmann in Germany in an article on mineral com-
position of pulmonary and suspended dusts, observe that secondary minerals
appear to inhibit or promote the effect of quartz in the lungs. They speci-
fically mention iron hydroxide as an inhibitor and anthracite coal as a pro-
moter.21 This phenomenon was also observed by some Russian scientists who con-
ducted an experiment in 1975 with calcium hydroxide coated silica particles.22
The same inhibitory effect was also reported by G. Reichel and others in 1975
describing the findings of relative absence of silicosis in a large German
iron mine work population.23 These observations, if confirmed to be effective
also with mica dust, may diminish the risk of use of mica when mixed in a
chemically basic matrix. A comparison experiment between the effect of pure
silica dust, pure muscovite dust and a mixture was performed by Starkov et al
at the Medical Institute in Irkutsk, USSR during 1970.2k In a 12 month exper-
iment using rats, the researchers measured the increase in collagen in rat
lungs after a one-time administration of dust intratracheally. The control
animals, exposed only to the intratracheal administration of the saline solution,
increased the lung collagen content by 2.5 percent over a period of 1 year. This
probably represents normal aging. The rats exposed to muscovite increased the
collagen content of the lungs by 4.4 percent, the mixed silica and mica dust
caused 5.5 percent increase and the administration of the pure quartz resulted in
9.9 percent of collagen increase in the lung in the same time frame. They also
observed that the collagen increase in the lungs progressed more rapidly after
6 months of the dust administration. This coincided with beginning of fibro-
blastic proliferation in the parenchyma of the lung.
In 1972, J. M. G. Davis in Britain reported on a series of experiments
regarding the fibrogenic effect of mineral dust injected in the pleural cavi-
ties of mice.25 One of the 16 materials used was chlorite, a relative of bio-
tite, "with a layered structure which in many ways resembles micas." Mice were
administered an interperitonial 10 milligram one-time dose. All materials
produced granulomas. Granulomas were produced within 2 weeks progressing to
a fibrosis stage and these fibers gradually being replaced by collagen in a
period of 6 to 8 months. This progression of events perhaps on a different
time scale, is fairly characteristic of the human experience. To put it
plainly, inert dust in the interstitial spaces of the lung causes a very low
523
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level gathering of cells around the dust particle. In a short time connective
tissue is formed around the particle. This tissue eventually hardens and
becomes scar tissue. Of course, I'm speaking of the particles which have not
been removed by mucous and ciliary action. The vast majority of inhaled par-
ticles is removed in that fashion. As a source of information, volume 200 of
the Annals of New York Academy of Sciences, published in 1972 is entirely
devoted to the lung and associated dust diseases. It is an excellent refer-
ence volume.
In 1973, the Industrial Toxicology Center in Lucknow, India, produced at
least four papers on body fluid response to mica (muscovite).
One paper describes the repeat of the collagen experiment conducted by
Starkov et al. that the observations are histological and microscopic, rather
than gravimetric. The process of fibrogenesis, as reported by Davis, is
confirmed. The transport of dust particles in the lung lymphatic system is
briefly discussed. The authors also claim hemolysis of erythrocytes by mus-
covite "in vitro."26 This finding has been challenged.
Polyvinyl pyridine N-oxide was found to inhibit erythrocyte hemolysis
"in vitro."2' The solubility of kaolin, micas and talc in presence or absence
of citrate, in buffer solution, defibrinated plasma and in serum is reported.28
Solubility and concentration of silica and silicates in the lung has apparently
a proportional negative influence on the enzymes which function in the lung.2^
In 1974 Pott, Huth and Fredericks in Germany, conducted a test to deter-
mine tumorigenic effect of fibrous dusts on rats. They used the direct inter-
peritoneal injection of dust suspended in saline solution.3^ Of the fifteen
materials tested, only biotite and hematite did not produce tumors. The dust
"fiber" size was less than five microns. The authors are convinced that dust
induced carcinogenesis depends on the shape factor. However, there were many
unanswered problems regarding this hypothesis.
Shanker and others reported on another experiment with Indian muscovite
in 1975.31 The experimental animals in this case were guinea pigs. The exper-
imental design was focused on the lymphatic transport and the cytotoxic effect
of mica in the lung. The cytotoxic effect was not considered pronounced and
the fibrotic lesions consisted of reticulin fibers (connective tissue). The
fibrogenic response was considered poor. The experiment was of 1 year dura-
tion after the intratradheal injection.
In 1976, in a French study, Berry, Henoc and others reported on the appli-
cation of electron microscopy and electron micro-defraction in differentiating
and detecting minerals found in the lungs of hospital patients.32 Of the 90
cases reviewed, 50 had a history of pneumoconiosis. In the cases associated
with silicoses, muscovite and biotite were also present.
A health hazard evaluation was conducted by NIOSH in 1976 in a mica paper
operation.33 The complaint was-nasopharyngeal irritation. The causal relation-
ship between mica and the symptomology present was suggestive but not conclusive.
524
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In 1975-76 the effects of phlogopite and muscovite dust in combination
with shellac and glythallic resin were studied in rats by Dianova and others
at the Moscow Medical Institute.3lf The study lasted 12 months. One group of
rats were intratracheally treated with 50 milligrams of either phlogopite,
muscovite, shellac or glythallic resin dust. The other group received the
same doses of mica dust except 20 milligrams of resin dust were added to each
dose to provide phlogopite/shellac, phlogopite/glythallic resin, muscovite/
shellac and muscovite/glythallic resin exposure simulation. When the animals
were sacrificed in the pure mica exposure group, internal organs such as liver,
heart and spleen showed uniform and nominal changes indicating a low level of
irritation. In the lung, granuloma was observed, in the early stages in 12
months. Shellac and resin dust caused a more pronounced hepatocytic reaction
in the liver and irritative reactions in the lungs.
The second group of animals (the combined materials) tested revealed that
the resin compound dust and shellac dust have an inhibiting effect on formation
of collagen in the lung as compared to mica exposure alone, even though aller-
genic or toxic effect on the rest of the body was more pronounced.
A concurrent industrial hygiene and medical study in a micanite plant
indicated airborne dust concentrations of the tested materials between 8.5 and
134 milligrams per cubic meter. Of 82 examined workers, 7 cases of pneumo-
coniosis were found. At the same time 6 cases of chronic bronchitis and
3 cases of lung calcifications were diagnosed. As a result of the animal
study, a combined threshold limit value of 2 milligrams per cubic meter for
the activity is recommended.
In 1977, Sedov and others from the Irkutsk Medical Institute describe a
study of 363 underground mica miners.35 The miners were exposed to dust con-
centrations up to 20 milligrams per cubic meter, peaking at 31 milligrams per
cubic meter. Airborne free silica content is reported between 2 and 71 percent.
Twenty-nine cases of pneumoconiosis and two cases of tuberculosis were found.
All affected miners showed bilateral fine grain fibrosis. Some had linear
thickening of the pleura. The first x-ray findings came after 13 to 17 years
of underground work. The authors conclude that pneumoconiosis develops after
a long period of time in the mines, and is characterized by diffuse fibrosis,
weak desquamic bronchitis, emphysema and presence of mica particles in the
lungs. The authors obviously are describing a mixed exposure situation.
In 1978 two Portugese authors report a case of lung fibrosis complicated
by an enlarged liver which, upon autopsy, is found to contain sarcoidal granu-
lomas. Both conditions are attributed to muscovite mica due to 7 years of
work history in mica grinding.36
Finally in 1979 a fairly extensive article on silicate pneumoconiosis
appeared in the American pathological literature. A simple pneumoconiosis
with lamellar birefringent crystals is reported by Brambilla et al, observed
during the autopsies of animals which died in the San Diego Zoo. In 100 autop-
sies of 11 mammaliam and 8 bird species, interstitial fibrosis was present in
20 percent of the cases. Seventy percent of the particles analyzed in the
autopsy specimens were muscovite mica or illite clay. The mica was also
present in atmospheric air samples obtained in the zoo. The authors also report
similar mica induced lesions found in humans living in the region of Southwest
525
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USA. It is a well written article touching on the naturally occurring envi-
ronmental exposures.37
Finally, a recently released MSHA informational report (IR#1111) lists
152 "minerals which may occur in fibrous habits or mineral suites which may
contain minerals of a fibrous habit."38 Illite and sericite are included.
Muscovite, biotite and phlogopite are not.
To summarize the findings and impressions from the literature search
conducted for this paper, I would like to make the following notes:
(a) Mica crystal lattice does not produce fibers even though some de-
posits and products may contain fibers of other minerals as iia^_
purities. Mica produces bladed or platy particles when crushed
or milled.
(b) Respirable mica particles trapped in the lung act as inert foreign
bodies. Generation of scar tissue results. TLV for mica was set
more than 20 years ago. Other than conversion to gravimetric
method of sampling, there has been no reason to change it.
(c) Experimentally pure mica dust produces less fibroses and at a
slower rate than the mixed dust or quartz particles after an equal
time and concentration exposure.
(d) Micas have not been reported to support tuberculosis in the lung.
(e) Micas have not been identified as carcinogenic, clinically or ex-
perimentally.
(f) Granuloma and functionally noticeable fibrogenesis due to mica
dust in humans is reported after very prolonged exposures to high
concentrations of dust. It almost has to be mixed occupational
exposure.
(g) Judging from the employee exposures and airborne concentrations
reported in the literature and from the medical survey data, the
prevention of fibrogenesis attributable to airborne mica dust
should be relatively simple.
(h) The word "fibrous" should be used more judiciously. In the con-
text of the lungs, it means protective body reaction, not related
to the shape or nature of the offending particle.
(i) The speculation that coating of the mica particles with other
material, especially chemically basic substances, inhibits fi-
brogenesis should be considered for experimentation.
There were a dozen references which were mentioned in literature, but
were not available for the preparation of this paper.
526
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Martin Marietta operates a phlogopite mine in Canada with a very large
and uniform deposit. As the question of presence or absence of fibers had
to be resolved, we decided to perform a sampling experiment. Seventeen trays
of exploratory core drillings were arbitrarily removed from storage and 1 to
2 inch sections were taken from each tray. The samples were ground to 40
mesh size. One electron microscope target was made from each ground sample.
Six photographs of each sample were produced by resetting the field selection
controls at random and refocussing. Seventeen sets of such pictures were
produced. None of the pictures showed the presence of fibers. Magnification
was held at 2,000 times. From the 17 sets, 3 were selected for presentation
today. Ten foot, 152 foot and 342 foot levels were somewhat arbitrarily
chosen. The six pictures in each set were reviewed for detail and clarity
and one was selected. One centimeter on the photograph equals 5 microns
in actual dimension. (See Appendix). Some flakes stand on edge and appear
acicular.
We also photographed 12 commercial samples obtained from other mica
producers. The fine residue in the sample bags was used to prepare the
electron microscope sample. Again, a series of six views at random were
obtained. The samples represent mica of the Soviet Union, Europe, India and
the United States. The same selection technique as in our own core samples was
used for presentation selection. Again we found no fibers. We will grant
that the method used is somewhat cursory, however, with certain refinements
it can be used as a statistical tool to anticipate presence or absence of
fibers in a commercially useful ore body. We will endeavor to show all of
the photographs obtained in the survey to interested parties.
REFERENCES
1. Lefond, S. J. et al., Industrial Minerals and Rocks, American Institute
of Mining, Metallurgical, and Petroleum Engineers, Inc., New York, NY,
1975, pp. 837-50.
2. Documentation of the Threshold Limit Values for Substances in Workroom
Air, American Conference of Governmental Industrial Hygienists,
Cincinnati, Ohio, Third Edition, 1971.
3. Lefond, S. J. et al., op cit., p. 841.
4. Shevchenko, A. M. et al., On the Mechanism of Lessening the Fibrogenic
Activity of Dust Processed with Calcium Hydroxide, Giglena Truda i
Professionalniye Zabol., Vol. 21, No. 8, 1977, (Russian; short English
abstract), pp. 31-34.
5. Zlobik, A. B., MICA-Mineral Commodity Profiles, U.S. Bureau of Mines*
Pittsburgh, PA, 1979.
6. Zlobik, A. B., MICA, Minerals Yearbook, U.S. Bureau of Mines, 1978-79.
7. Policard, A., The Action of Mica Dust on Pulmonary Tissue, Journal of
Industrial Hygiene, Vol. 15, No. 3, 1934, pp. 160-64.
527
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8. Dreessen, W. C. et al., Pneumoconiosis Among Mica and Pegmatite Workers,
U.S. Public Health Bulletin, U.S. Government Printing Office, Washington,
B.C., No. 250, 1940, pp. 1-74.
9. American Conference of Governmental Industrial Hygienists, TLV's for
Chemical Substances and Physical Agents in the Workroom Environment with
Intended Changes for 1979^
10. Vestal, T. F. et al., Pneumoconiosis Among Mica and Pegmatite Workers,
Industrial Medicine, Vol. 12, 1943, pp. 11-14.
11. ACGIH, op cit., Documentation of the Threshold Limit Values for Substances
in Workroom Air.
12. Smith, Adelaide R., Pleural Calcification Resulting from Exposure to
Certain Dusts, American Journal of Roentgenology, Vol. 67, 1952,
pp. 375-382.
13. King, E. J. et al., Tissue Reaction to Sericite and Shale Dusts Treated
With Hydrochloric Acid; An Experimental Investigation on the Lungs of
Rats, Journal of Pathology and Bacteriology, Vol. 59, 1947, pp. 324-27.
14. Silicosis in Mica Mining in Bihar, India, Monthly Review of the Division
of Industrial Hygiene, New York State Department of Labor, Vol. 33,
No. 7, 1954, pp. 25-28.
15. Heimann, H., et al., Note on Mica Dust Inhalation, Archives of Industrial
Hygiene and Occupational Medicine, Vol. 8, No. 6, 1953, pp. 531-32.
16. Tripsa, R., et al., Experimental Studies^ on Pneumoconiosis Induced by
Mica Dust, Medicina Del Lavoro, Vol. 57; No. 8-9, 1966, French; English
summary), pp. 492-500.
17. Vorwald, A. J. et al., Mineral Content of Lung in Certain Pneumoconioses,
Archives of Pathology, Vol. 74, 1962, pp. 17-24.
18. Cralley, Lewis J., et al., Source and Identification of Respirable
Fibers, American Industrial Hygiene Association Journal, Vol. 29,
1968, pp. 129-135.
19. Campbell, W. J. et al., Selected Silicate Minerals and Their Asbestiform
Varieties, United States Department of the Interior, Bureau of Mines,
Information Circular 8751, 1977, p. 27.
20. Mihajlov, P., et al., Occupational Lesions Associated with the Production
and Processing of Asbestos and Mica, Higiena i Zdraveopazvane, Vol. 11,
No. 2, 1968, (Bulgarian), pp. 145-150.
21. Bruckman, E., et al., The Mineral Composition of Pulmonary and Suspended
Dusts and Their Silicogenic Effect, Staub-Reinhalt, Luft, Vol. 29, No. 1,
*>January 1979, (English Ed.), pp. 6-17.
528
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22. Schevchenko, A. M. et al., op cit.
23. Reichel, G., et al., The Action of Quartz in the Presence of Iron
Hydroxides in the Human Lung, Inhaled Particles, IV, 1975, pp. 403,
408-410.
24. Starkov, M. V. et al., Biochemical and Morphological Evaluation of
Collagen Generation in the Lungs (of Experimental Animals) Caused by
Mica and Mixed Dust from Mines in Irkutsk Region, Gigiena Truda i
Professionalniye Zabol., Vol. 15, No. 8, (Russian), 1971, pp. 42-43.
25. Davis, J. M. G., The Fibrogenic Effects of Mineral Dusts Injected into
the Pleural Cavity of Mice, British Journal of Experimental Pathology,
Vol. 53, 1972, pp. 190-201.
26. Raw, J. L. et al., Effect of Mica Pust^on the Lungs of Rats,
Experimentalle Pathologie, Vol. 8, No. 3, 1973, (Jena, E. Germany),
pp. 224-231.
27. Kaw, J. L. et al., Hemolytic Activity of Mica Dust and Its Relation to
Polyvinylpuridine N-Oxide, Experimentalle Pathologie, Vol. 8, No. 5-6,
1973, (Jena, E. Germany), pp. 349-355.
28. Rahman, Qamar et al., Solubility of Kaolin, Talc and Mica Dusts Under
Physiological Conditions, Environmental Physiology and Biochemistry,
Vol. 3, No. 6, pp. 286-294.
29. Rahman, Qamar et al., Relation Between Solubility of Silicates and
Enzyme Inhibition in Rat Lung Homogenate (in Vitro Studies), Environ-
mental Physiology and Biochemistry, Vol. 3, No. 6, 1973, pp. 281-285.
30. Pott, F. et al., Tumorigenic Effect of Fibrous Dusts in Experimental
Animals, Environmental Health Perspectives, Vol. 9, 1974, pp. 313-315.
31. Shanker, R. et al., Effect of Intratracheal Injection of Mica Dust on
the Lymph Nodes of Guinea Pigs, Toxicology, Vol. 5, 1975, pp. 193-199.
32. Berry, J. P. et al., Pulmonary Mineral Dust, American Journal of
Pathology, Vol. 83, No. 3, 1967. pp. 427-456.
33. National Institute for Occupational Safety and Health, Health Hazard
Evaluation Determination, U.S Department of Commerce, NTIS, Report
No. 75-193-335, 1976, pp. 1-16.
34. Dianova, A. V. et al., The Problem of the Combined Action of the Dust
of Mica and Resins Used in the Production Micanite Articles, Gigiena i
Sanitarnaya, Vol. 7, 1976, (Russian; English summary), pp. 33-37.
529
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35. Sedov, K. R. et al., The Morphological Characterization of Mica
Pneumoconiosis in a Mine in the Irkutsk Region, Gigiena Truda i
Professionalniye Zabol., Vol. 21, No. 2, 1977, (Russian), p. 48.
36. Pimentel, I. C. et al., Pulmonary and Hepatic Granulomatous Disorders
Due to the Inhalation of Cement and Mica Dusts, Thorax, Vol. 33, No. 2,
1978, pp. 219-227.
37. Brambilla, C. et al., Comparative Pathology of Silicate Pneumoconiosis,
American Journal of Pathology, Vol. 96, No. 1, 1979, pp. 149-170.
38. Asbestiform and/or Fibrous Minerals in Mines, Mills and Quarries,
U.S Department of Labor, Mine Safety and Health Administration,
Informational Report IR 1111, 1980.
530
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APPENDIX
531
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MARTIN MARIETTA CORPORATION
PHLOGOPITE - CANADIAN - CORE SAMPLE 152 FT. LEVEL
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MARTIN MARIETTA CORPORATION
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PHLOGOPITE - CANADIAN - CORE SAMPLE 10 FT. LEVEL
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MARTIN MARIETTA CORPORATION
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PHLOGOPITE - CANADIAN - CORE SAMPLE 342 FT. LEVEL
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MARTIN MARIETTA CORPORATION
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PHLOGOPTTE - USSR
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MARTIN MARIETTA CORPORATION
MUSCOVITE - EUROPEAN
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MARTIN MARIETTA CORPORATION
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MUSCOVITE - INDIA
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MARTIN MARIETTA CORPORATION
en
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MUSCOVITE - INDIA - MICRONTZED
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MARTIN MARIETTA CORPORATION
MUSCOVITE - NORTH CAROLINA
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MARTIN MARIETTA CORPORATION
vO
MUSCOVITE - NORTH CAROLINA - FINE GRIND
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MARTIN MARIETTA CORPORATION
MUSCOVITE - NORTH CAROLINA - COARSE GRIND
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MARTIN MARIETTA CORPORATION
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MUSCOVITE - SOUTHERN NORTH CAROLINA
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DISCUSSION ON MICA
QUESTION (Mr. Stumpf): I am from U.S. Mineral Products. I noticed in
your chart, from one of the micas, that you reference vermiculite,
which I understand at times does have some fibers. You indicate
that your Canadian mica contained no fibers. Are fibers associated
with some of the other micas and in what part of the United States?
ANSWER (Mr. Lusis): I really cannot answer that truthfully. My personal
knowledge of the presence of particulates in mica is restricted
to the 156 electronmicroscope slides which I observed.
In reviewing the literature, I did see a couple of pictures,
especially in the foreign literature, which would claim to be mica
and there would be a few particles in them. But in the cursory
survey we did here and from a rough statistical point of view, I
am fairly well convinced that in the U.S. markets of the ground
micas., you have to go back to the manufacture process. Most of
U.S. ground mica is washed before you get it. That is part of
the separation process of kaolin; you take kaolin out and then
you get some mica from it. So, again, in some European micas
you could get fibers; but from the commercial samples we re-
ceived, I did not see any.
554
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HEALTH EFFECTS OF VERMICULITE
by
Dr. James Lockey and Dr. Stuart M. Brooks*
University of Cincinnati College of Medicine
Cincinnati, Ohio
ABSTRACT
Vermiculite is a geologic name given to a group of hydrated laminar minerals
which are aluminum-iron magnesium silicates resembling mica in appearance.
When subjected to heat it has the unusual property of exfoliating or expand-
ing due to the interlaminar generation of steam. The present study includes
an analysis of the physical and chemical characteristics of vermiculite; an
industrial hygiene survey of a plant which utilized crude vermiculite in an
industrial process; and the results of some preliminary information on a
cross-sectional morbidity study of exposed workers.
Depending on source location raw vermiculite may be contaminated with
tremolite-actinolite asbestos. Contamination is greatest in vermiculite
obtained from Montana and least from vermiculite obtained from South America.
Preliminary investigations of workers suggest a high prevalence rate of
pleural and possibly parenchymal lung disease. There were nine employees
identified with benign pleural effusions, believed to be on an occupational
basis. It appears that adverse health effects from vermiculite are the
results of contamination with tremolite-actinolite asbestos and not related
to vermiculite itself.
This report will review various physical and chemical properties of
vermiculite, and present preliminary data on a medical survey of employees
using vermiculite as a carrier for fertilizers and herbicides.
CASE REPORT
Dr. John Pryor from Ohio State University first observed what appeared
to be an unusual number of pleural effusions in employees of a fertilizer
plant using vermiculite as a carrier.1
A typical patient was a 40-year old male in a good state of health until
five months prior to hospital admission, when he developed an upper respiratory
*Presented by Dr. James Lockey.
555
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infection, cough, shortness of breath and loss of appetite. He had one flight
dyspnea and could walk one block at a slow pace on a level surface.
The patient worked for 15 years with a company manufacturing fertilizers
and pesticides using vermiculite as a carrier. The majority of his time was
spent in an area processing raw vermiculite from an unexpanded to expanded
(exfoliated) form. There was no other significant employment history.
The chest X-ray revealed bilateral pleural effusions greater on the left
than right, and bilateral lower lobe linear fibrosis. Pulmonary function
tests were consistent with restrictive lung disease with no evidence of
airway obstruction. Examination of the pleural fluid revealed grossly bloody
fluid with a red cell count >200,000. A left-sided decertification procedure
was performed in which a 5 mm thickened pleura was removed. Subsequently, a
right-sided pleurectomy was performed in which 10-25 mm of thickened pleura was
removed. Pathological examination showed chronic inflammation and fibrosis;
no asbestos bodies were noted in lung or pleural tissue. No asbestos fibers
were found by X-ray diffraction.
There have been nine additional cases of pleural effusions in employees
working at this plant. The majority of cases were diagnosed after 1974 with
two cases reported between 1969-1971. The mean age of the employees was 46
years, and the mean duration of employment was 15.5 years. The location of
the effusion was on the right in seven cases, left in two cases, and bilateral
in one case. One employee had evidence of pulmonary fibrosis. The majority
of these employees worked in one area of the plant processing raw vermiculite.
Seven employees had examination of the pleural fluid. Five were grossly
bloody with white counts >1,000. Five of seven were exudative in nature with
protein content >2.5 gm. Five employees had pleural biopsies with evidence
of inflammation and/or fibrosis.
CHARACTERIZATION AND USES OF VERMICULITE
Vermiculite is the geological name given to the group of hydrated laminar
minerals that are aluminum-iron-magnesium silicates. The crystal structure
is similar to mica and biotite. The mineral can expand or exfoliate up to
20 times its original size. This property is dependent on the generation of
steam from the intrinsic water content with the application of heat between
300-1500°F. As it expands, it becomes curved or "worm-like," hence the name
vermiculite from vermicular meaning "to produce worms."2*3
Vermiculite is a secondary mineral derived from trioctahedral micas,
phlogopite, or biotite, by geochemical alteration. The geologic deposits are
usually associated with mica. ** The chemical composition of vermiculite is
shown in Table I. The Si02 content is 37 percent and the aluminum con-
tent is 14 percent. The high aluminum content is in contrast to the much
lower content in asbestos. Before exfoliation, the water content is 20 percent,
A potential health problem with vermiculite is the contamination Of the
raw ore with asbestos. Recent studies utilizing X-ray diffraction, dispersion
staining with polarized light microscopy, scanning electron microscopy with
556
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energy dispersion X-ray analysis, and transmission electron microscopy with
selected area electron diffraction revealed varying concentrations of tremolite-
actinolite in North American ores. Tremolite-actinolite belongs to the
calcium amphibole family and they are very similar in crystal structure and
elemental composition.s»6
The previously identified chrysotile-like fiber in South African ore is
believed to be rolled-up scrolls of vermiculite and not asbestos fibers. These
scrolls form at the cracks in vermiculite plates. They are of tubular morphology
and tend to form bundles similar to chrysotile. The transition to scroll
configuration includes the reduction of magnesium and aluminum concentrations
relative to silicon.7 .
Vermiculite has multiple uses including insulation, waste filtration, soil
additive, and as packaging material. As an aggregate in plaster and concrete,
it decreases the weight and adds insulating and fire resistant properties.
In mines vermiculite is used as a sealant for control of spontaneous
heating, sealing air crossings, fire-proofing road ways, and for consolidating
pack sides. Processed to a finer grade, it is used as a sound-deadening
material, in flame resistant paints, handboards, plasters, and as fillers in
plastics, rubber, roofing and flooring material. In agriculture, it is used as
a carrier for herbicides, insecticides, fungicides, fertilizers, seeds, and as
a bulking agent in animal feed.
INDUSTRIAL HYGIENE DATA OF PLANT
Industrial hygiene measurements were initiated in 1972. The first
measurements for total dust and fiber content according to OSHA criteria for
asbestos fibers were elevated within the expander area. These initial high
levels probably represented the general condition of the working environment
within the expander area since the plant was constructed. With the institution
of procedure changes and environmental controls, the company has been in
compliance with present and pending OSHA regulation for total dust and
asbestos fibers.
PILOT MEDICAL SURVEY
Because of the apparent high number of pleural effusions in employees
within the vermiculite expander area of the plant, a pilot medical survey
was initiated in 1979. Chest films and pulmonary function tests of 125
employees were reviewed. There appeared to be an increase prevalence of
pulmonary abnormalities in employees processing vermiculite to an expanded
form. Confirmation of this preliminary data awaits analysis of a recently
completed cross-sectional epidetniological study of all employees of this plant.
REFERENCES
1. Pryor, J.: Personal Communication, 1980. Ohio State University School
of Medicine, Columbus, Ohio.
2. Singleton, R. H.: Vermiculite. From Mineral Facts and Problems, U.S.
Dept. Interior, Bureau of Mines, Bulletin 667, 1975.
557
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3. Otis, L. M.: Vermiculite. From Mineral Facts and Problems, U.S. Dept.
Interior, Bureau of Mines, Bulletin 585, 1960.
4. Baweja, A. S., et al.; Mineralogy and Cation Exchange Properties of
Libby Vermiculite Separates as affected by Particle-size Reduction,
Clays and Clay Minerals. 22:253, 1974.
5. Walter C. McCrone Assoc., Inc., Chicago, Illinois. Consulting:
Ultramicroanalysis.
6. Navy Environmental Health Center, Laboratory Division. Cincinnati,
Ohio.
7. Chatfield, E. J.: Ontario Research Foundation, Mississauga, Ontario.
558
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TABLE I. CHEMICAL ANALYSIS OF UNEXFOLIATED VERMICULITE
SiO_
A1203
Fe,0
FeO
JMnO
MgO
CaO
Na20 _
K20_
H2O at 150 °C
Type c
Theoretical
vermiculite
36.71
1 A IK
J.4 . J.D
4.43
24.62
20.09
>r Sourc
Libby
Mont.
41.0
to n
J.O . U
7.0
21.0
1.0
1.0
1.0
11.0
e of Materia
Palabora,
South
Africa
39.37
1.25
i •> no
JLz . Uo
5.45
1.17
.30
23.37
1.46
.80
2.46
11.20
1
West
Chester
Pa. ( jeffer-
isite)
34.30
1 fi ^ft
7.41
1.13
20.41
21.14
From Otis, L.M.
(3)
559
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DISCUSSION ON VERMICULITE
QUESTION (Mr. Carton) : I am with the EPA. I would suggest if you are using
controls from the plant, you would not get a definitive study since
the majority of the employees would be exposed to some of the
material in the air surrounding the plant.
The second point, please elaborate on the vermiculite fiber that
was felt initially to be chrysotile.
ANSWER (Dr. Lockey): In answer to your second comment, the initial
analyses of vermiculite (prior to 1977) revealed possible contami-
nation with chrysotile asbestos. Later analysis confirmed the
presence of tremolite-actinolite in Montana Ore.
Analysis of South African ore by scanning electron microscopy with
energy dispersion X-ray analysis and transmission electron micro-
scopy with selected area electron diffraction revealed fiber
morphology believed to represent vermiculite scrolls.
QUESTION (Mr. Carton): Was this fibrous? And if it was, have you accounted
for it by measuring it in your industrial hygiene survey? You may
be missing a fibrous compound if all you are looking for is just
the asbestos.
ANSWER (Dr. Lockey): The vermiculite scrolls are considered fibrous by
OSHA criteria. A complete qualitative analysis has not yet been
performed on the nonasbestos fibers obtained during industrial
hygiene sampling. This analysis will be completed in the near future.
QUESTION (Mr. Carton): I think it is unusual to be getting abnormal results
in such a short amount of time with asbestos exposure. Should you
not be thinking of something else other than asbestos?
ANSWER (Dr. Lockey): The time interval for the development of pleural
changes including pleural effusions after asbestos exposure is
consistent with the exposure history of the plant under study. These
benign effusions often occur within 10 years of exposure. Toxicity
studies in animals with asbestos-free vermiculite and asbestos-
contaminated vermiculite need to be performed to determine their
relative toxicity.
REMARK (Mr. Carton): I was concerned about the fact that you are using
people in the plant as controls and not an outside group.
REMARK (Dr. Lockey): We plan to use, as our control population, employees
from a physically separate plant with no history of exposure to
vermiculite.
REMARK (Dr. Wiley): I am from the University of Maryland. I think Eric
Chatfield has published some photographs of the curled edge of
vermiculite that indicates that they look very similar to chrysotile.
560
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REMARK
QUESTION
ANSWER
REMARK
REMARK
REMARK
I would like to make another comment. The word "tremolite" and ^
the word "asbestos" are not synonymous, nor is the word "actinolite
a synonym for the word "asbestos." I think if you are going to claim
certain vermiculite deposits contain asbestos, you need more than the
presence of mineral tremolite or actinolite to make a judgment.
(Dr. Lockey): There is some controversy concerning the classification
of tremolite-actinolite. The chemical and crystal composition of
tremolite and actinolite are very similar. Present OSHA asbestos
regulations include tremolite.
(Dr. Ross): I am from the U.S. Geological Survey.
these analyses?
What labs did
(Dr. Lockey): The more recent analyses (after 1977) of the vermicu-
lite ores were done by independent labs under the contract to the
company under study and the South African Mining Company. They
include the Navy Environmental Health Center in Cincinnati, the
Ontario Research Foundation under Dr. Eric Chatfield, and the
Walter C. McCrone Associates, in Chicago.
(Dr. Ross): I would like to make a general comment. A Geological
Survey science department in this country that teaches minerology/
petrology would have no trouble in making these identifications.
(Dr. Lockey): A majority of the vermiculite analytical work was
performed by independent laboratories prior to our involvement. An
independent complete analysis of all commercial sources of vermicu-
lite needs to be undertaken.
(Dr. Langer): I am from Mt. Sinai. I will have to take issue with
the.geologist from the United States Geological Survey. If an
analyst does not have available the knowledge of the physical
character of the mineral as it occurs in geological outcropping
(either tensile strength or fiber flexibility), you cannot use the
term asbestiform or asbestos for any submicroscopic fiber. Asbestos
applies to specific physical conditions of fibers in the natural
aggregated state.
If one examined fibrous material by electron microscopy, whether
it is by transmission electron microscopy or by scanning electron
microscopy, one must examine a population of fibers. One must also
determine by selected area electron diffraction the orientation of
the fiber being examined. This is considered critical in that
asbestiform minerals tend to cleave along the 010 and the 100 planes,
whereas rock-forming amphiboles have the more "normal" cleavage,
either 210 or 110. When examining mineral fibers, the only one that
you can identify with any surety is chrysotile. Here also some
structural clarification may be required. Comminuted amphibole
fibers requires a statistical study of particle-orientation to
561
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determine if you are looking at a true asbestos fiber. If the nature
of the material on the gross aggregate level is unknown, the term
asbestos cannot be used.
REMARK (Dr. Wiley): I am from the University of Maryland. I would take
issue with Dr. Langer. I think you can probably make a pretty good
estimate from population of particles based on their width, their
length, their shape analysis as to whether they represent a population
of true asbestos fibers, or a population of cleavage fragments.
Orientation may not be required.
REMARK (Dr. Langer): Dr. Wiley is absolutely correct. When one has a
population of the same mineral fiber, one can determine size-
distribution characterization, and on the basis of the width distri-
bution, you can determine if you are looking at amosite, crocidolite,
or at some of the other asbestos varieties. That is possible only if
you are looking at a pure monominerallic material.
If you are looking at an aggregate population, such as the population
that you might encounter in a vermiculite deposit, which may contain
an extremely fibrous tremolite in one place and blocky tremolite
fragments in another place, one must use the more detailed
characterization. Dimensional and morphological analysis does not
help.
QUESTION (Mr. Teitlebaum) : I am from the EPA. I noticed in your data on the
length of employment in relationship to workers with pleural
effusions, it seemed like the latent period was much more shorter
than one normally sees with asbestos. I was wondering what working
hypothesis you are using to explain that or to investigate that
further.
ANSWER (Dr. Lockey): The interval for the development of benign pleural
effusions after asbestos exposure can range from a few months to
over 30 years. Our data is consistent with this.
The company under study does incorporate a number of herbicides and
pesticides into their product. If we find a significant increase
in pleural changes within the study population that is not isolated
to the vermiculite-exposed workers, then we will need to look for
another etiology.
QUESTION (Dr. Menuite): Have any quantitative analyses been done on the
amount of tremolite-actinolite present in the various vermiculite
ores?
ANSWER (Dr. Lockey): Quantitative analyses has been done, but the data is
not available at this time.
562
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OPENING REMARKS: NATURAL NON-FIBROUS SUBSTITUTES: TALC
by
Arthur M. Langer, Ph.D.
Mt. Sinai School of Medicine
of the City University of New York
New York, New York
Good Evening members of the panel, ladies and gentlemen. Tonight we are to
address the topic "Is talc a possible non-fibrous asbestos substitute?".
ASBESTOS
The need to substitute for asbestos in a number of products, and a number
of workplaces, has become increasingly more important as data become available
which delineate the full extent of its health effects. These data are
impressive when one considers the excess neoplastic risk associated with fiber
inhalation, including those effects produced in synergism with cigarette
smoke. Recent information, discussed at the IARC (International Agency for
Research on Cancer) in the fall of 1979, suggests that no threshold limit
value exists in so far as fiber exposure and increased risk to cancer is
concerned. Therefore, in addition to controlling dust in the workplace, one
finds it increasingly more important to limit fiber exposures of all kinds,
and reduce asbestos' pervasiveness throughout our industrialized society.
t
SUBSTITUTION
There are a number of important questions which may be asked of all of
us before considering a substitute material to take the place of asbestos:
will the substitute material perform comparably on a technical basis?; will
the substitute material provide greater "safety" as compared with asbestos,
for the worker, the consumer and for the environment?; is the substitute
material available in relative abundance?; does the economic outlook favor
substitution, including both direct and indirect costs to the manufacturer
and eventually to the consumer?; where will substitution take place first?
Substitution is clearly indicated, without undue deliberation, if
asbestos fiber is incorrectly used to begin with, e.g., chrysotile asbestos
in children's papier maches, where a clay is easily substituted. The issue
here is clear-cut: the asbestos fiber was present in an "unbound" state,
with a great potential for liberation and inhalation; the fiber was present
in a material for which substitution could easily be achieved; the
563
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substituted material would have equalled or economically benefitted.the manu-
facturer; the substitute clearly produced a safe product.
TALC
One of the materials currently considered as a substitute for asbestos is
"talc". To properly gauge how this material may be used as a substitute it
is important to define the nature of talc; determine if its biological poten-
tial is clearly known, and provide a sound comparative base with asbestos.
THE NATURE OF TALC
The geological occurrence of talc has recently been detailed by Rohl
et al. (1976), 257-258. In that paper, the following was described:
"Talc rocks (including those commercially worked) are formed by
several complex geological processes reacting upon many possible,
chemically diverse preexisting rock types. Hydrothermal alteration
of magnesia and silica-rich ultramafic rocks, under a range of low-to-
moderate temperatures and pressures, may produce talc. Thermal
metamorphism of silica-rich dolomite (CaMg(C03)2 will produce talc as
well. These processes, however, also commonly result in the formation
of a number of other coexisting mineral phases, predominantly hydrous
magnesium silicates. Some of these, for example, anthophyllite,
tremolite, and serpentine minerals (including chrysotile), occur as
microscopic intergrowths with talc, as macroscopic nodules, or even
as discrete zones within or adjacent to talc. Talc rock is therefore
generally not monominerallic but is often a mixture of minerals that
may vary widely with respect to kind and quantity. Phlogopite, a
magnesium mica, and chlorite, a group of minerals related to micas, are
also commonly associated with talc. Some of these associated mineral
phases (may be) asbestiform amphiboles and chrysotile". "Conversely,
talc has been described as a common accessory mineral in commercial
asbestos deposits (Hurlbut and Williams, 1935). Talc deposits may be
zoned, with different mineral assemblages physically changing in
occurrence and proportions over extremely variable distances, ranging
from centimeters to tens of meters. Mineral phases in such deposits
may include talc plates and fibers, tremolite and anthophyllite fibers,
intergrowths of amphibole and talc, serpentine minerals (which may
include chrysotile), and free silica (quartz) (Ross et al., 1968).
The fiber intergrowth is often such that even extensive beneficiation
may not yield a pure product. Thus, where fine-grained intergrowths of
talc and tremolite occur, the processed product will likely contain re-
sidual tremolite".
"It is generally recognized that various commercial grades of talc are
marketed in the United States. Hildick-Smith (1976) has stated that a
talc suitable for pharmaceutical purposes, used in cosmetic and toiletry
products, contains at least 90% talc mineral and no detectable asbestos.
564
-------
Such stated compositional restrictions are not placed on industrial grade
talcs. One study demonstrated that a number of industrial talcs contained
substantial quantities of tremolite, up to 87% by weight of the sample
(Schulz and Williams, 1942)".
It is of special importance to note that contaminant amphibole minerals may be
true asbestiform (asbestos) varieties, may comminute as acicular cleavage
fragments or may form more equant (blocky) cleavage fragments. Morphology may
be critical in estimating biological potential. The general chemistry of talc,
its structure and crystal habit, the mineral nature of talc intergrowths and
other information are provided in Rohl et al., 1976. The above data indicate
that talc deposits may consist of intimate admixtures of the mineral talc
(occurring as both plate and fiber) quartz, amphibole minerals of different
varieties and habits (including true asbestiform varieties) and serpentine
minerals (including chrysotile). The important question then is, "if talc is
considered as a substitute, which talc do we mean?"
HEALTH EFFECTS
There are a number of health effects which have been observed associated
with occupational exposure to talc. These effects have been described in
detail in Rohl et al., 1976:
"A fine, diffuse, bilateral, progressive fibrosis was observed among
miners and millers of tremolite talc in Georgia {Dreessen, 1933; Dreessen
and Dalla Valle, 1935). Siegal et al, (1943) studied a population of
workers mining and milling tremolite and anthophyllite-bearing talc
deposits in New York State. In addition to the bilateral fibrosis,
pleural plaques, similar to those encountered in asbestos workers, were
observed. Review of postmortem material in this study indicated that
asbestos bodies were present in lung tissue. These findings were also
reported in cases of severe pneumoconiosis in tremolite millers by
Daymen (1946), and by Porro and Levine (1946). Millman (1947) reported
that exposure to cosmetic-grade talc produced nodular fibrosis in workers.
No quartz was detected in the dust. The author concluded that talc
itself was capable of producing scarring. The observation was supported
in studies by Reichman (1944) and by Wyers (1949) and in a study of talc
miners and millers in Italy where exposure to pure talc produced a 10%
incidence of pneumoconiosis in workers (Parmeggiani, 1948). Excess
deaths attributed to pneumoconiosis have been reported among workers in
northern Italy mining talc considered to be free of asbestiform fibers
(Rubino et al., 1976).
Some investigators have held that fibrous talcs (not differentiated as
talc or asbestos fiber) are biologically more hazardous than platy talcs.
For example, in a review of the literature by Porro, et al. (1942),
Gloyne and Gardner are referred to as considering that the clinical,
radiological, and pathological disease states of asbestosis and talcosis
are very similar. There are several reports of the occurrence of
asbestos bodies in the lung tissue of workers exposed to talc (Daymen,
1946; Hobbs, 1950; Kleinfeld et al., 1973; McLaughlin et al., 1949;
Porro et al., 1942).
565
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Several studies suggest that fibrous talcs are more dangerous as a result
of the included asbestos' fiber. For example, McLaughlin et al (1949)
compared fibers in talc with the proportion of fibers recovered from
the lung tissue of an exposed worker. A larger concentration of fibers
was found in the tissues as compared with the raw talc. Talc
pneumoconiosis was reaffirmed by Kleinfeld and Messite (1960) in their
study of the New York State talc workers.
In a study by Kleinfled et al. (1967) it was demonstrated that talc
pneumoconiosis accounted for almost 30% of excess deaths among the talc
miners and millers. Most of these were due to the complication of
pneumoconiosis, cor pulmonale. However, 21% of the 91 deaths recorded
were due to malignant tumors: lung carcinoma, pleural fibrosarcoma, and
stomach, colon, and pancreatic cancers. A peritoneal mesothelioma was
reported as well. In addition to these tumors, retroperitoneal sarcoma,
hepatoma, and leukemia were also found. Statistical evaluation of these
data indicated that a 3- to 4-fold excess of cancers existed in this
group, as compared to a matched control population.
The biological activity of both tremolite and anthophyllite fibers has
been known for some time, and both have been cited as asbestos minerals
by Merewether (1930) and Noro (1946). Asbestos disease among workers
(and others exposed to anthophyllite and tremolite) has been reported
(Burilkov and Badajov, 1970; Kiviluoto, 1960; Meurman, 1968; Meurman et
al. 1974, Scherpers, 1965; Wegelius, 1947; Weiss and Boettner, 1967).
Recent experimental data also indicate that tremolite fibers are bio-
logically active (Graham and Graham, 1967). Some investigators have
suggested that inorganic fiber fibrogenicity and carcinogenicity is
limited only by its ability to reach the alveolar space (Holt et al.,
1965; Pott and Friedrichs, 1972; Pott et al., 1974; Robock and Kloster-
kotter, 1976; Stanton and Wrench, 1972).
Wagner et al. (1975) reported lung scarring in Wistar rats with pure talc,
exposed by inhalation. The severity and extent of the lung scarring was
comparable to that produced by chrysotile asbestos under identical
experimental conditions. In addition to lung scarring, ingestion of talc
was reported to be associated with leiomyosarcoma of the stomach as
well as one adenoma and several sarcomas of the uterus. However, the
exposure levels were high and the numbers of observed tumors small, so
that statistical validation of the carcinogenic potential of pure talc
and its relevance to human exposures were not achieved.
There are also extensive data concerning hazards associated with exposure
to silica or trace metals, particularly nickel and chromium (National
Research Council, 1975). Analytical data are presented here that suggest
possible disease potential and the need for investigation in these
areas."
It is obvious that the biological effects are in part related to the nature
of the talc d'eposits, i.e., the nature of the materials to which the workers
are exposed.
566
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WHICH TALC?
It is now recognized that a variety of mineral deposits yield an indus-
trial mineral substance called "talc". It is equally obvious that disease
patterns vary from geological locality to geological locality which reflects,
in part, the mineralogical nature of the deposit. The question may then be
asked, if talc is to be considered as a non-fibrous substitute for asbestos,
which talc is safe?; are there any talcs which are safe?; are data available
to suggest which of these talcs may safely be used as a non-fibrous
substitute?
This evening we will hear a report by Drs. Gamble and Griefe which con-
tains information on an industry-wide cross-sectional epidemiologic and
industrial hygiene survey of talc workers. This study includes the "pure
talc" of Montana (of Yellowstone and Beaverhead Mines), and "contaminated"
Texas talc (of Palestine and Van Horn), and the North Carolina talc (Murphy
Mine) which consists of a mixture of talc plates and talc fiber. These are
the data which are urgently needed to guide the various agencies in their
search for safe asbestos substitutes.
REFERENCES
Burilkov, T. and Badajov, L. 1970. Bin Beitrag zum endemischen Auftreten
doppelseitiger Pleuraverkalkungen. Prax. Pneumal. 24:433-438.
Daymen, H. 1946. Latent silicosis and turberculosis. Am. Rev. Tuberculosis
53:554-559.
Dreessen, W. C. 1933. Effects of certain silicate dusts in the lungs. J.
Indust. Hyg. 15:66-78.
Dreessen, W. C. and Dalla Valle, J. M. 1935. The effects of exposure to dust
in two Georgia talc mills and mines. Publ. Health Repts. 50:1405-1415.
Graham, J. and Graham R. 1967. Ovarian cancer and asbestos. Environ. Res.
1:115-128.
Hildick-Smith, G. 1976. Talc: Review of epidemiologic studies. Proc.
Br. Occup. Health Soc., Edinburgh, Sept. 1975. In press.
Hobbs, A. A. 1950. A type of pneumoconiosis. Am. J. Roentgenol. Radiol
Therap. 58:488-497.
Holt, P. F., Mills, J. and Young, D. K. 1965. Experimental asbestos with
four types of fibers: Importance of small particles. Ann. N.Y. Acad.
Sci. 132:87-98.
Hurlbut, C.S., Jr. and Williams, O.R. 1935. The mineralogy of asbestos
dust. J. Indust. Hyg. 17:289-293.
567
-------
Kiviluoto, R. 1960. Pleural calcification as a roentgenologic sign of non-
occupational endemic anthophyllite asbestosis: Acta Rad. Scand.
194:1-67.
Kleinfeld, M. and Messite, J. 1960. Problem area in pneumoconiosis. Arch.
Environ. Health 5:428-437.
Kleinfeld, M. , Messite, J. , Kooyman, 0. and Zaki, M.H. 1967. Mortality among
talc miners and millers in New York State. Arch. Environ. Health 14:
663-667.
Kleinfeld, M., Messite, J. and Langer, A. M. 1973. A study of workers exposed
to asbestiform minerals in commercial talc manufacture. Environ. Res.
6:132-143.
McLaughlin, A., Rogers, E. and Dunham, K. C. 1949. Talc pneumoconiosis. Br.
J. Indust. Med. 6:184-194.
Merewether, E. R. A. 1930. The occurrence of pulmonary fibrosis and other
pulmonary affections in asbestos workers. J. Ind. Hyg. 12:198-222,
239-257.
Meurman, L. 0. 1968. Pleural fibrocalcific plaques and asbestos exposure.
Environ. Res. 2:30-46.
Meurman, L.O., Kiviluoto, R. and Hakama, M. 1974. Mortality and morbidity
among working populations of anthophyllite asbestos miners in Finland.
Br. J. Indust. Med. 31:105-112.
Millman, N. 1974. Pneumoconiosis due to talc in the cosmetic industry.
Occup. Med. 4:391-394.
National Research Council. 1975. Nickel. Washington, B.C. National Academy
of Sciences.
Noro, L. 1946. On the history of asbestosis. Acta. Pathol. Microbiol.
Scand. 23:53-59.
Parmeggiani, L. 1948. Le pneumoconiosi dei minatori e dei mugnai del
talco nel Pinerolese. Rass. Med. Ind. 17:16-17.
Porro, F. W. and Levine, N. M. 1946. Pathology of talc pneumocioniosis with
report of an autopsy. North. N.Y. State Med. J. 3:23-25.
Porro, F. W., Patton, J. R. and Hobbs, A. A. 1942. Pneumoconiosis in the
talc industry. Am. J. Roentgenol. 47:507-524.
Pott, F. and Friedrichs, K. H. 1972. Tumoren der Ratte nach i.p. Injektion
faserformiger Staube. Naturwissenschaften 59:318.
Pott, F., Huth, F. and Friedrich, K. H. 1974. Tumorigenic effects of
^fibrous dust in environmental animal. Environ. Health Persp. 9:313-315.
568
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Reichman, V. 1944. Uber Talkumstaublunge. Arch. Gewerbepathol. Gewerbehyg.
12:319-322.
Robock, K. and Klosterkotter, W. 1976. The biological effect of dusts of
asbestos and asbestos cement products. Proc. Br. Occup. Health Soc.
Edinburgh, Sept. 1975. In press.
Rohl, A. N., Langer, A. M., Selikoff, I. J., Tordini, A., Klimentidis, R.,
Bowes, D. R., Skinner, D. L. 1976. Consumer talcums and powders:
Mineral and chemical characterization. J. Toxicol. Env. Health. 2:
255-284.
Ross, M., Smith, W. L. and Ashton, W. H. 1968. Triclinic talc and associated
amphiboles from Gouverneur Mining District, New York. Am. Mineral. 53:
751-769.
Rubino, G. F., Scansetti, G. Piolatto, G. and Romano, C. A. 1976. Mortality
study of talc miners and millers. J. Occup. Med. 18:186-193.
Schepers, G. W. H. 1965. Discussion. Epidemiology of mesothelial tumors in
the London area. Ann. N.Y. Acad. Sci. 132:579-602.
Schylz, R. Z. and Williams, C. R. 1942. Commercial talc, animal and mineral
studies. J. Ind. Hyg. 24:75-82.
Siegal, W., Smith A. R., and Greenburg, L. 1943. The dust hazard in tremolite
talc mining, including roentegenological findings in talc workers. Am.
J. Roentgenol. 4:11-29.
Stanton, M. F. and Wrench, C. 1972. Mechanisms of mesothelioma induction
with asbestos and fibrous glass. J. Natl. Cancer Inst. 48:797-821.
Wagner, J. C., Berry, G., Cooke, T. J., Hill, R. J., Pooley, F. D. and
Skidmore, J. W. 1975. Animal experiments with talc. Proc. Br. Occup.
Health Soc. Edinburgh. Sept. 1975. In press. •
Wegelius, C. 1947. Changes in the lungs in 126 cases of asbestosis observed
in Finland. Acta Radiol. 28:139-152.
Weiss, B. and Boettner, E. 1967. Commercial talc and talcosis. Arch.
Environ. Health 14:304-308.
Wyers, H. 1949. Asbestos. Postgrad. Med. J. 631-638.
569
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CROSS-SECTIONAL EPIDEMIOLOGIC AND INDUSTRIAL HYGIENE SURVEY
OF TALC WORKERS MINING ORE FROM
MONTANA, TEXAS, AND NORTH CAROLINA
By
John Gamble*
Alice Greife*
John Hancock
National Institute for Occupational Safety and Health
Appalachian Laboratory for Occupational Safety and Health
944 Chestnut Ridge Road
Morgantown, West Virginia 26505
ABSTRACT
Two hundred and ninety-nine miners and millers exposed to talc from Mon-
tana, Texas, and North Carolina were examined in a cross-sectional study of
respiratory symptoms, lung function, and chest X-rays. This population com-
prises the bulk of talc workers outside of New York and Vermont. Work his-
tories were taken from personnel records. Personal respirable dust samples
were collected for all jobs and used in the estimate of exposm'e for each job.
Cumulative exposure was calculated by adding together the results of multiply-
ing the estimated exposure for each job times the length of time worked in that
job. The average time worked was 7, 6, and 10 years and average exposure
(cumulative exposure divided by the total time worked) was 1.2, 2.6 and 0.3
mg/m3 in Montana, Texas, and North Carolina respectively. Free silica content
of bulk samples was low (below the limit of detection in Montana, 1.5 percent
in North Carolina, and 2.2 percent in Texas). No fibers were observed under
the light microscope. Under the transmission electron microscope, tremolite
and antigorite fibers (0.5 - 3 pm diameter and 4 - 30 ym length) were observed
in the Texas talc, acicular particles (aspect ratios 5-10 to 1 and some diam-
eters less than 0-1 ym) in North Carolina talc, and no fibers in the Montana
talc. There were no differences among the regions by age, smoking and exposure
groups in the prevalence of cough (19 percent), phlegm (23 percent), dyspnea
(5 percent), and bilateral pleural thickening (5 percent). None of the symp-
toms showed any consistent association with years worked or cumulative exposure.
Comparisons of the prevalence of symptoms and pleural thickening were made with
blue collar workers, potash miners, aboveground and underground coal workers,
and New York talc workers after indirect adjustments for age and smoking. The
*Presented by John Gamble and Alice Greife.
570
-------
prevalence of cough was not different than potash, blue collar, and aboveground
coal workers, and less than underground coal and New York talc workers. The
prevalence of phlegm was no different than blue collar workers, and was less
than potash, coal, and New York talc workers. There was no difference in the
prevalence of dyspnea between the study populations and potash, blue collar,
New York talc, and was less than the prevalence of coal workers. There were
two cases (less than 1 percent) of grade 1 small rounded opacities. The
prevalence of bilateral pleural thickening among workers 40 years or older
was 7 percent, 16 percent, and 14 percent in Montana, Texas, and North
Carolina, and 0 percent, 0 percent, and 10 percent in those less than 40. No
nonsmoker had bilateral pleural thickening and there was a slight tendency
for the prevalence to increase with exposure. Workers with bilateral pleural
thickening had lung function 10 to 20 percent below workers with no pleural
thickening. They had also worked twice as long (13 years) and an average of
13 years between beginning exposure to talc and the time of the X-ray. The
prevalence of bilateral pleural thickening was elevated in all talc workers
compared to all nontalc workers. Reduced lung function showed no association
with exposure. After adjustments for age, height, and smoking, FEVj and FVC
was no different than potash miners and blue collar workers and was 2 to 5
percent less than coal workers. Flow rates at low lung volumes were 4 to 19
percent less than all of the comparison populations.
Although the amount of time worked by the study population was short, there
were no increases in symptoms or pneumoconiosis nor biologically signifi-
cant reductions in lung function. Bilateral pleural thickening was signifi-
cantly increased. The prognostic significance of the pleural thickening is
unknown.
MEDICAL PORTION
INTRODUCTION
Talc is a mineral with a wide variety of uses in paint, paper, ceramics,
cosmetics, plastics, roofing products, textile material, rubber, lubricants,
corrosion proofing composition, fire extinguishing powders, cereal polishing,
water filtration, insecticides, to name a few. Pure talc is a hydrated mag-
nesium silicate, but the talc found in nature has quite a variable chemical
and mineralogical composition. The mineral contaminant in talc of most con-
cern is asbestos. The hazard from exposure to "pure" talc free of asbestos
contamination is not well documented. The purpose of this study was to
ascertain the effects on the respiratory system (symptoms, lung function,
radiographic) of exposure to talc dust from the three major U.S. ore deposits
that had not been studied.
Talc workers in seven mines and eight mills in Montana, Texas, and North
Carolina were studied in this cross-sectional study. The mines in Montana and
Texas were typical open pit operations, while the underground mine in North
Carolina employed square set timbers and stopes. In each mine examined,
typical mucking techniques were employed. ANFO (ammonium nitrate and fuel oil)
was the most common type of explosive used.
571
-------
Following extraction of the ore, the talc is hand sorted to remove extraneous
material as in Montana, or goes directly from the mine to the primary crusher.
Froth flotation and heavy metal separation techniques were not used in any
facility examined. Following initial crushing the talc is calcined, as in the
case of ceramic grade talcs, before it was ground using dry grinding methods
into the final product. Once the talc was ground to the appropriate mesh size,
it might be sterilized as in the case of pharmaceutical grade talc, and then
shipped in bags or bulk. The commercial uses of talc in the deposits studied
are as follows. Montana talc is used in cosmetics, paints, paper, ceramics,
and steatite. Texas talc is used in ceramic tile and insecticides. North
Carolina talc is used in cosmetics, crayons, paint, rubber, Pharmaceuticals,
and steatite.
The specific questions being addressed in this paper are:
• What is the prevalence of symptoms and abnormal radiographic
findings by exposure categories within each region? What is
the association of exposure with reduced lung function?
• After adjustment for confounding variables, how does the study
population compare with other mining and nonmining populations
in the prevalence of symptoms, abnormal radiographic findings,
and mean lung function?
METHODS
The study population consisted of workers mining and milling talc from
three regions of the United States: Montana, Texas, and North Carolina.
There was over 90 percent participation. Although several different companies
may be involved, the results for each region are combined, as the character-
istics of the talc in each region are similar. As there were few regional
differences in symptom prevalence and lung function, analysis of combined
regions is also presented.
The industrial hygiene portion of the study took pjace in every facility
in which morbidity data was collected and is discussed by Alice Greife.
All workers were administered a British Medical Research Council respi-
ratory questionnaire by trained interviewers. Non-talc work history was ob-
tained in the interview; work experience at the talc facility was obtained
from company records. Standard posteroanterior chest radiograms were read by
three "B" readers using the ILO U/C 1971 scheme. The films were read inde-
pendently without knowledge of age, occupation, or smoking history. The
median of the three readings was used for analysis. Flow volume curves from
a minimum of 5 forced expiratory maneuvers were obtained and recorded on mag-
netic tape using an Ohio 800* rolling seal spirometer. Values from the max-
imum envelope were used for analysis. Before and after shift spirometry was
administered to workers on the day shift, and personal environmental samples
*Disclaimer
572
-------
were also collected on these workers. The results of the personal environ-
mental sampling were used to estimate average talc dust exposure for each job.
This estimate was then used to calculate cumulative talc dust exposure by
multiplying job exposure x time, and adding the results of each multiplication;
the units are mg/m3 x years. The association of lung function and exposure
(cumulative exposure and years worked) was analyzed by multiple regression.
Exposure variables were defined in several ways. Years worked in the talc
industry was divided into <5 years, 5 to 9, and 2dO years worked categories
for analysis of symptoms and pleural thickening. For analysis of symptoms
and pleural thickening cumulative exposure was divided into low (<2 mg/m x
years) , medium (2 to 6 mg/m3 x years) , and high (>6 mg/m3 x years) exposure
groups. These categories were chosen to obtain nearly equal numbers for each
group. Differences by region and department (classified according to whether
the majority of work was done in the mine, mill, crayon plant, or other) were
also analyzed.
The prevalence of selected symptoms and pleural thickening was compared
to several mining and nonmlning populations after indirect adjustment for
smoking and using the age distribution of all populations. Pulmonary function
prediction equations were calculated for each smoking category of these com-
parison populations. The observed lung function of each worker from the study
population was compared to the predicted lung function of the appropriate
smoking category of the comparison population. The individual observed to
predicted ratios from all smoking categories and regions were added together
and multiplied by 100 to give percent predicted lung function. Female pre-
diction equations were available for only the blue collar comparison popula-
tions. Percent predicted lung function comparisons with the mining
population are therefore for males only.
Demographic Characteristics
Table 1 summarizes the characteristics of the three regions. The North
Carolina population was slightly older, had worked slightly longer, and had a
higher proportion of smokers than the other two regions. Texas had the highest
average and cumulative exposure of all the regions, and the smokers smoked
fewer cigarettes per day.
Only 11 percent of the workers in Montana and Texas had worked 10 years
or more compared to 38 percent in North Carolina. Most of the study popula-
tion in Montana and Texas had worked less than 5 years (66 percent and 73
percent respectively). About 20 percent in all regions had worked from 5 to
9 years. The correlation of age by years worked, age by cumulative exposure,
and years worked by cumulative exposure respectively was 0.63, 0.41, and 0.48
in Montana, 0.36, 0.12, and 0.12 in Texas, and 0.51, 0.33, and 0.44 in North
Carolina.
There was one case each in Texas and Montana of Grade 1 small rounded
opacities and no cases of pleural calcification. There were no other radio-
graphic interpretations of pneumoconiosis. Cytology on sputurns collected
from workers 35 years of age or older revealed no cytology suggestive of
malignancy.
573
-------
TABLE 1. DEMOGRAPHIC CHARACTERISTICS OF THE TALC WORKER
POPULATIONS BY REGION
Montana
n
Age
Height (cm)
Years worked
Cumulative exposure
Texas
177
(S
(S
(S
(S
.D.)
.D.)
.D.)
.D.)
34.9
175.5
6.6
5.9
(11
(8
(6
(7
.5)
.8)
• 3)
.6)
38
173
5
11
North
71
.0
.0
.5
.3
(13
(6
(5
(45
.7)
.9)
.7)
.1)
43.1
172.5
10.1
3.0
Carolina
51
(12.6)
(8.3)
(8.6)
(4.8)
(mg/m3-years)
Average exposure (S.D.)
(mg/m3)
Nonsmokers (%)
Ex-smokers (%)
Pack years (S.D.)
Cigarettes/day (S.D.)
Smokers (%)
Pack years (S.D.)
Cigarettes/day (S.D.)
Education - n (%)
< 8th grade
9-12 grade
>12th grade
1.21 (0.94)
33
21
15.7 (17.9)
23 (15)
45
17.9 (16.9)
20.4 (11.0)
10
126
38
(5.7)
(72.4)
(21.9)
2.64 (7.12) 0.28 (0.33)
20
27
21
17
13.3 (20.7) 18.2 (16.5)
12 (14) 21.4 (15.7)
54 62
14.3 (19.7) 23.7 (21.8)
14.5 (11.1) 20.4 (10.0)
46 (66.7) 22 (43.1)
22 (31.9) 26 (51.0)
1 (1.4) 3 (5.9)
574
-------
Symptoms and Radiography (Internal Comparisons;
Tables 2 through 9 summarize the prevalence of cough, phlegm, shortness
of breath, and pleural thickening by region, smoking, and exposure.
The prevalence of cough was 18 percent, 17 percent, and 27 percent in
Montana, Texas, and North Carolina respectively. There were no apparent
differences in the prevalence of cough among the three regions by age and
smoking categories. Prevalence tended to increase with age (except North
Carolina) and smoking (Table 2). There were no apparent differences in the
prevalence of cough among the regions by exposure groups, and no apparent
association of cough with exposure either within each region or when all
regions were combined (Table 3).
The prevalence of phlegm was 18 percent, 17 percent, and 25 percent in
Montana, Texas, and North Carolina respectively. There were no apparent
differences in the prevalence among the three regions by age or smoking cate-
gories. Prevalence increased consistently with age only among ex-smokers.
Except for Texas, the prevalence of phlegm was highest in smokers with ex-
smokers intermediate (Table 4). There were no apparent differences in the
prevalence of phlegm among the regions by exposure groups, and no apparent
association of phlegm with exposure either within each region or when regions
were combined (Table 5).
The prevalence of dyspnea was low compared to cough and phlegm: 4 per-
cent, 9 percent, and 6 percent in Montana, Texas, and North Carolina respec-
tively. There were no apparent differences among the regions by age or smok-
ing categories. There was no apparent association of smoking with dyspnea
(nonsmokers and ex-smokers had the highest prevalence) . Dyspnea increased
with age in all smoking categories (Table 6). There were no apparent diff-
erences in the prevalence of dyspnea among the regions by exposure groups,
and no apparent association with years worked or cumulative exposure (Table 7)
The prevalence of pleural thickening was 4 percent, 13 percent, and 18
percent in Montana, Texas and North Carolina respectively, and was signifi-
cantly less in Montana after adjustment for age or years worked. The number
of those with bilateral pleural thickening* was 5 of 6, 4 of 9, and 6 of 9 in
the three regions. There was no difference in the prevalence of bilateral
pleural thickening among the three regions by age or smoking categories.
Prevalence increased with age (there was 1 in the <40 year age group in
Montana and 2 in the <_ 40 year age group in North Carolina with bilateral
pleural thickening), but the association of age and pleural thickening was
significant only among smokers. There was no significant association of
smoking and bilateral pleural thickening, although the prevalence was zero
among nonsmokers, and highest among smokers (Table 8). There were no differ-
ences in prevalence among the regions by exposure group (except the medium
*A11 the cases of pleural thickening were extent 1, except for one case each
in the low and high cumulative exposure groups in Texas.
575
-------
TABLE 2. PREVALENCE OF COUGH AMONG TALC WORKERS BY AGE, SMOKING,
AND REGION
Age
<40
% (95% C.I.)
>40
% (95% C.I.)
Total
% (95% C.I.)
Montana
Nonsmoker
Ex-smoker
Smoker
Total
Texas
Nonsmoker
Ex-smoker
Smoker
Total
North Carolina
Nonsmoker
Ex-smoker
Smoker
Total
Total (All Regions)
Nonsmoker
Ex-smoker
Smoker
Total
7
0
27
16 (10-24)
10
11
15
13 (5-28)
0
33
38
29 (13-51)
7 (2-16)
7 (1-21)
26 (18-35)
21 (15-29)
19
10
38
23 (13-35)
25
40
8
23 (11-42)
0
17
37
26 (12-45)
15 (5-32)
19 (9-34)
30 (18-45)
23 (15-32)
10 (4-21)
5 (0.05-17)*
29 (19-40)*
18 (13-25)
14 (3-39)
26 (11-50)
13 (5-28)
17 (9-28)
0 (0-25)
22 (4-56)
38 (21-58)
27 (15-42)
10 (5-20)*
13 (6-24)
27 (20-35)*
19
Cough = Answering yes to the question: "Do you usually cough on most days
for as much as 3 months each year?"
Summary; No differences among regions by age and smoking.
Tendency to increase with age.
Smokers generally have the highest prevalence.
*95% C.I. do not overlap.
576
-------
TABLE 3. PREVALENCE OF COUGH AMONG TALC WORKERS BY EXPOSURE
AND REGION
Montana
% (95% C.I.)
Texas
% (95% C.I.)
North
Carolina
% (95% C.I.)
Total
(All regions)
% (95% C.I.)
Years Worked
<5
5-9
>10
Cumulative
Low
Medium
High
17
14
30
Exposure
15
17
17
(11-25)
(6-30)
(9»36)
(6-28)
(9-28)
(9-29)
20
18
0
7
31
11
(10-35)
(3-50)
(0-32)
(1-22)
(15-51)
(2-33)
30
33
20
19
50
22
(14-53)
(12-65)
(7-41)
(9-36)
(22-78)
(4-56)
19
19
21
14
25
16
(14-25)
(10-31)
(10-36)
(8-23)
(17-35)
(9-26)
Summary: No difference among regions by exposure.
No association with years worked.
No association with cumulative exposure.
577
-------
TABLE 4. PREVALENCE OF PHLEGM AMONG TALC WORKERS BY AGE, SMOKING,
AND REGION
Age
<40
% (95% C.I.)
>40
% (95% C.I.)
Total
% (95% C.I.)
Montana
Nonsmoker
Ex-smoker
Smoker
Total
Texas
Nonsmoker
Ex-smoker
Smoker
Total
North Carolina
Nonsmoker
Ex-smoker
Smoker
Total
Total (All Regions)
Nonsmoker
Ex-smoker
Smoker
Total
12
17
27
20 (13-29)
20
22
8
14 (5-29)
0
0
23
14 (4-34)
12 (5-24)
13 (5-29)
33 (24-43)
23 (16-30)
6
14
23
17 (8-29)
25
40
8
23 (11-39)
0
33
42
32 (16-51)
7 (1-22)
27 (14-43)
26 (15-40)
22 (15-31)
10
10
26
18
21
32
8
17
0
22
34
25
11
21
31
23
(4-21)
(6-30)
(16-36)
(13-26)
(6-50)
(15-57)
(2-21)
(9-28)
(0-25)
(4-56)
(18-54)
(14-40)
(5-20)*
(12-33)
(24-39)*
Phlegm: Answering yes to the question: "Do you usually bring up phlegm from
your chest for as much as three months each year?"
Summary: No difference among regions by age or smoking.
No association with age.
Smokers have highest prevalence.
*95% C.I. do not overlap.
578
-------
TABLE 5. PREVALENCE OF PHLEGM AMONG TALC WORKERS BY EXPOSURE AND REGION
Montana
% (95% C.I.)
Texas
% (95% C.I.)
North
Carolina
% (95% C.I.)
Total
(All regions)
% (95% C.I.)
Years Worked
<5
5-9
>10
Cumulative
Low
Medium
High
19
12
30
Exposure
17
18
17
Summary: No differences
(13-27)
(4-26)
(14-53)
(8-30)
(9-30)
(8-30)
20
9
13
7
27
17
(10-34)
(0.5-37)
(0.6-50)
(1-22)
(11-46)
(5-38)
among regions by exposu
20
33
25
13
50
33
re.
(7-41)
(12-65)
(10-47)
(5-29)
(22-78)
(10-71)
19
16
25
13
24
19
(14-25)
(8-26)
(14-39)
(7-21)
(16-34)
(11-30)
No association with years worked.
No association with cumulative exposure.
579
-------
TABLE 6. PREVALENCE OF DYSPNEA AMONG TALC WORKERS BY AGE,
SMOKING, AND REGION
Age
<40
% (95% C.I.)
% (95% C.I.)
Total
% (95% C.I.)
Montana
Nonsmoker
Ex- smoker
Smoker
Total
Texas
Nonsmoker
Ex-smoker
Smoker
Total
North Carolina
Nonsmoker
Ex-smoker
Smoker
Total
Total (All Regions)
Nonsmoker
Ex-smoker
Smoker
Total
2
6
2
2 (0-6)
10
0
0
2 (0-12)
0
0
0
0 (0-14)
4 (0.5-13)
3 (0.2-16)
1 (0-5)
2 (0-5)*
6
10
5
7
25
20
8
19
17
33
0
10
11
16
6
10
3
8
2
(2-16) 4
14
11
5
(8-37) 9
9
22
0
(3-24) 6
(3-27) 6
(1-18) 10
(0-12.5) 3
(5-17.5)* 5
(0-11)
(2-21)
(0-8)
(2-9)
(3-39)
(2-32)
(0-16)
(4-18)
(0-37)
(4-56)
(0-10)
(1-17)
(2-14)
(4-20)
(1-7)
Dyspnea = Answering yes to the question: "Do you get short of breath walking
with people your own age on level ground?"
Summary; No differences among regions by age or smoking.
Increased prevalence with increased age.
No association with smoking.
*95% C.I. do not overlap.
580
-------
TABLE 7. PREVALENCE OF DYSPNEA AMONG TALC WORKERS BY EXPOSURE AND REGION
North Total
Montana Texas Carolina (All regions)
% (95% C.I.) % (95% C.I.) % (95% C.I.) % (95% C.I.)
Years Worked
<5
5-9
>10
Cumulative
Low
Medium
High
5
0
5
Exposure
6
2
3
Summary: No differences
(3-12)
(0-9)
(0-22)
(1-16)
(0-7)
(0-11)
among the
10
0
13
7
8
11
reg
(4-22)
(0-25)
(0-50)
(1-22)
(1-23)
(2-33)
Ions by e
5
0
10
3
0
22
xposu
(0-22)
(0-24)
(2-29)
(0-17)
(0-27)
(4-56)
re.
6
0
8
5
3
7
(3-10)
(0-6)
(2-20)
(2-11)
(1-8)
(2-14)
No association with years worked.
No association with cumulative exposure.
581
-------
TABLE 8. PREVALENCE OF BILATERAL PLEURAL THICKENING AMONG TALC WORKERS
BY AGE, SMOKING AND REGION
Age
<40 >40
% (95% C.I.) % (95% C.I.)
Montana
Nonsmoker
Ex- smoker
Smoker
Total
Texas
Nonsmoker
Ex-smoker
Smoker
Total
North Carolina
Nonsmoker
Ex-smoker
Smoker
Total
Total (All Regions)
Nonsmoker
Ex-smoker
Smoker
Total
Summary ; No differences
0
0
2
1
0
0
0
0
0
33
8
10
0
6
2
2
among
0
5
14
(0-5) 7 (2-16)
0
0
33
(0-9) 16 (6-34)
0
0
22
(2-28) 14 (5-30)
(0-7) 0 (0-11)
(0.3-24) 3 (0-15)
(0-7)* 22 (11-36)*
(0-6) 11 (5-18)
regions by age and smoking.
Total
% (95% C.I.)
0
4
5
3
0
0
11
6
0
11
16
12
0
4
9
5
(0-7.5)
(0-17)
(1-13)
d-8)
(0-27)
(0-17)
(4-25)
(2-15)
(0-27)
(0-44)
(7-32)
(4.5-25)
(0-6)
(0-14)
(5-15)
Prevalence tends to increase with age.
No bilateral pleural thickening among nonsmokers,
*95% C.I. do not overlap.
582
-------
TABLE 9. PREVALENCE OF BILATERAL PLEURAL THICKENING AMONG TALC
WORKERS BY EXPOSURE AND REGION
Montana
% (95% C.I.)
Texas
% (95% C.I.)
North
Carolina
% (95% C.I.)
Total
(All regions)
% (95% C.I.)
Years Worked
<5
5-9
>10
Cumulative
Low
Medium
High
0
3
22
Exposure
2
I
0
7
Summary: No difference
(0-4)
(0-14)
(8-44)
(2-11)
(0-7)-
(2-17)
1
*
J
4
9
14
4*
8
6*
among regions
(0-14)
(0-37)
(0-55)
(0-17)
(1-23)*
(0-27)
by exposure
5
0
26
6
30
13
(0-22)
(0-25)
(11-50)
(1-20)
(9-62)
(0-50)
2
3
23
4
5
8
(0-5)
(0-10)1
( 12-38) J
(1-10)
(1-12)
(3-17)
1
*
J
except medium exposure
group in North Carolina has a higher prevalence than medium
exposure group in Montana.
Increased prevalence of bilateral pleural thickening with
increasing years worked.
No association with cumulative exposure.
*95% C.I. do not overlap.
'''Extent = 2.
583
-------
exposure group in Montana was less than in North Carolina). Prevalence
increased in all regions with increasing years worked, but was significant
only for Montana and the combined regions. There was no association of
bilateral pleural thickening with cumulative exposure (Table 9). There were
no apparent differences in working experiences or respiratory disease between
the regions among talc workers with and without pleural thickening. No worker
showed pleural calcification on X-ray.
Table 10 compares workers with and without pleural thickening. Those
with any pleural thickening were about 10 years older than those without.
Workers with bilateral pleural thickening on average weighed more (11-15 Kg),
had worked longer (6 years), and had higher average and cumulative exposures
than those with unilateral or no pleural thickening. The average time between
first exposure to talc and the date of the chest radiograph was 4.5 years for
those with unilateral pleural thickening and 13.1 years for those with bilat-
eral pleural thickening. The "latency" by region was 10 years for Montana and
Texas and 17.7 years for North Carolina. All pulmonary function parameters
of those with bilateral pleural thickening were reduced. Those with unilat-
eral pleural thickening generally had intermediate lung function values.
Symptoms and Radiography (External Comparisons)
Table 11 summarizes the characteristics of the comparison populations.
The coal miner populations were examined as part of the second round of the
National Study of Coalworkers' Pneumoconiosis, and were divided into white
males working only underground and only aboveground. The potash mines were
part of the MSHA/NIOSH epidemiologic-industrial hygiene study of metal and
nonmetal underground miners.1*2 White male miners from 6 potash mines were
used for comparison. All of the potash mines used diesel engines. The New
York talc population were miners and millers of New York talc containing
tremolite and anthophyllite.3*4*5 The blue collar comparison population was
part of the recently completed NIOSH blue collar control study and included
male and female workers for such Industries as electronics, synthetic textiles,
bakeries and bottling plants.6
The workers in the comparison populations had worked longer in their cur-
rent industry than had the study populations. The mining populations generally
were heavier smokers than the study populations and the blue collar workers.
All of the mining comparison groups had occupational exposures in the form of
coal dust, diesel fumes and potash (primarily potassium chloride and sodium
chloride), and talc containing asbestiform fibers.
Tables 12 through 15 summarize the age and smoking adjusted rates of
cough, phlegm, dyspnea, and pleural thickening of the talc workers and com-
parison populations.
The prevalence of cough among the 40 or older workers in the study pop-
ulation was less than underground coal, and less than underground coal and
New York talc when all ages were considered. There was no difference in the
prevalence of cough of the study population and blue collar workers at either
age level (Table 12).
584
-------
TABLE 10. COMPARISON OF WORKERS WITH AND WITHOUT PLEURAL THICKENING
(REGIONS COMBINED)
No PT
Unilateral
Bilateral
n
Frequency (95% C.I.) .
Cough (%)
Phlegm (%)
Dyspnea (> Grade 2)
Obliteration of cos-
tophrenic angle
Unilateral
Bilateral
Means (S.E.)t
Age
Height -cm
Weight -kg
Years worked
Cumulative exposure
(mg/m3 x years)
Average exposure
(mg/m3)
255
18
18
5
2
0.4
(14-23)
(14-23)
(3-8)
(0-5)
(0-1)
22 (4-56)
22 (4-56)
11 (0-44)
11
0
(0-44)
(0-29)
36.4
174.0
76.6
6.7
5.1
(0.8)
(0.5)
(0.8)
(0.4)
(0.4)
1.1 (0.1)
46.7 (3.4)
170.1 (2.1)
80.5 (4.9)
6.9 (2.2)
2.4 (0.7)
0.87 (0.3)
15
33 (14-63)
33 (14-63)
7 (0-30)
13
0
(2-37)
(0-19)
47.7 (2.2)
175.3 (2.0)
91.9 (4.3)
13.4 (2.3)
34.1 (24.6)
3.2 (2.5)
'"Latency"
-years
FEVi/FVC x 100 *
FEVx (L)*
FVC (L)*
Peak Flow
FEF50
FEFys
(L/sec)*
77
3
4
8
4
1
—
.1
.56
.61
.37
.10
.40
(0.
(0.
(0.
(0.
(0.
(0.
7)
05)
06)
15)
13)
06)
4
80
3
4
7
4
1
.5 (1
.2 (2
.47 (0
.29 (0
.62 (0
.19 (0
.45 (0
.4)
.7)
.19)
.22)
.56)
.49)
.21)
13
72
3
4
7
3
1
.1
.5
.08
.19
.02
.30
.24
(2.3)
(2.2)
(0.16)
(0.18)
(0.45)
(0.40)
(0.18)
tLung function least square means adjusted for differences in sex, age,
height, weight, and smoking status.
*Pleural thickening is a significant variable in the linear regression model.
585
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TABLE 11. CHARACTERISTICS OF COMPARISON POPULATIONS FOR TALC STUDY
n
Age
Height (cm)
Years Worked
(Range)
Nonsmokers
Ex-Smokers
Mean Pack Years
Mean Cigarettes/Day
Smokers
Mean Pack Years
Mean Cigarettes/Day
00 Mean Current N02
°* Concentration (ppm)
Mean Current Total Dust
(mg/m3)
Respirable Dust
Fibers >5 um/cc
(LM)
(S.D.)
(S.D.)
(S.D.)
(X)
(X)
(S.D.)
(S.D.)
(X)
(S.D.)
(S.D.)
New York
Talc
121
39 (12)
176 ( 6)
11 (9)
(0-33)
21
31
26 (28)
28 (19)
48
26 (17)
27 (11)
N.A.
N.A.
t 0.77 Mine
t 0.87 Mill
t 5.4 Mine
t 4.8 Mill
Potash
875
41 (13)
176 ( 6)
16 (13)
(0-50)
20
28
23 (20)
25 (14)
52
28 (23)
25 (12)
*0.90
*3.45
N.A.
N.A.
N.A.
Aboveground
Coal
509
44 (12)
175 ( 6)
18 (13)
(0-55)
22
32
24 (19)
23 (12)
46
27 (18)
22 ( 9)
N.A.
N.A.
1.44 ft
N.A.
N.A.
Underground
Coal
5722
39 (13)
174 ( 6)
15 (13)
(0-56)
21
23
17 (18)
19 (12)
56
17 (14)
17 ( 8)
N.A.
N.A.
1.36 ft
N.A.
N.A.
Blue
Male
843
38 (14)
173 ( 7)
12 (12)
(0-50)
25
23
21 (23)
23 (15)
52
23 (19)
23 (11)
N.A.
N.A.
N.A.
N.A.
N.A.
Collar
Female
597
40 (13)
162 ( 6)
11 (10)
(0-46)
49
10
9 (10)
16 (12)
42
17 (13)
19 ( 9)
N.A.
N.A.
N.A.
N.A.
N.A.
* Personal samples, from Attfield (1978) and Sutton, et al. (1978)
N.A. - Not available
t From Dement, et al. (1980)
ft Collected between the first and second rounds of the National Coalworkers Study. The 25 coal mines were in both
the first and second rounds of examinations of the coal study.
-------
TABLE 12. COMPARATIVE RATES OF COUGH AMONG TALC WORKERS COMPARED TO OTHER
MINING POPULATIONS AND BLUE COLLAR WORKERS. STRATIFIED BY AGE
AND INDIRECTLY ADJUSTED FOR SMOKING.
<40
% (95% C.I.)
AGE
^40
% (95% C.I.)
TOTAL
(95% C.I.)
Montana
Texas
North Carolina
Combined Study Population
New York Talc
Potash Miners
Underground Coal
Aboveground Coal
Blue Collar
16.7 (10-25)
13.6 ( 5-29)
28.6 (13-51)
17.4 (12-24)
36.2 (24-50
20.5 (17-25)
18.1 (16-20)
16.0 (11-23)
15.2 (11-18)
24.1 .(14-37)
21.8 (11-42)
23.5 (10-40)
23.7 (16-33)
36.0 (24-50)
28.3 (24-32)
44.9 (43-46)
35.3 (30-41)
18.5 (15-23)
20.1 (14-27)
1-7.4 ( 9-28)
26.2 (15-40)
20.3 (15.5-25)
36.1 (28-45)
24.1 (20-27)
30.5 (29-32)
24.9 (22-29)
16.7 (14-20)
Cough a Answering yes to the question: "Do you usually cough on most days
for as much as three months each year?"
Summary;
<40: Study populations no different than comparison populations.
>40: Montana, Texas, and North Carolina «underground coal.
Total: Montana and Texas «New York talc and underground coal.
Combined study population «New York talc and underground coal
workers.
587
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TABLE 13. COMPARATIVE RATES OF PHLEGM* AM08G TALC WORKERS COMPARED
TO OTHER MTNIHG POPULATIONS AND BLUE COLLAR WORKERS.
STRATIFIED BY AGE AND DfDIRECTLY ADJUSTED FOR SM0KIHG
Age
<40 >40 Total
Z (95Z C.I.) Z (95Z C.I.) Z (95Z C.I.)
Montana talc 20.2 (14-29) 18.5 (10-31) 19.4 (14-26)
Texas talc 13.8 ( 5-29) 21.8 (11-42) 17.5 ( 9-28)
Berth Carolina talc 12.9 ( 4-34) 31.6 (18-52) 21.5 (11-35)
Combined study population 17.8 (13-25) 23.2 (15-32) 20.3 (16-25)
Hew York talc 33.0 (22-47) 38.5 (26-53) 35.5 (27-45)
Potash ainers 25.4 (21-29) 34.3 (3O-38) 29.5 (27-34)
underground coal 32.7 (31-35) 50.0 (46-53) 40.7 (39-41)
Aboveground coal 18.6 (13-26) 40.7 (35-47) 28.8 (25-33)
Blue collar 16.2 (13-19) 18.5 (15-24) 17.3 (14-21)
aPhleg» = Answering yes to the question: "Do you usually bring up
phleg* for as much as 3 Months each year?"
SUMMARY:
<4O: Montana J*«H Texas «underground coal.
Combined study population «underground coal.
>40: Montana talc «coal workers.
Texas «underground coal.
Combined study population «coal workers.
TOTAL: Montana «Sew York talc, potash, underground coal.
Texas and Borth Carolina «underground coal.
Combined study populations «Hew York talc, potash, and coal
workers.
588
-------
TABLE 14. COMPARATIVE RATES OF DYSPWEA* AMOBG TALC WORKERS COMPARED
TO OTHER MDIIBG POPULATIONS AND BLUE COLLAR WORKERS.
STRATIFIED BY AGE" AMD INDIKECTLY ADJUSTED FOR SMOKING
Age
<40 >40 Total
Z (95Z C.I.) Z (95Z C.I.) Z (95Z C.I.)
Montana 2.6 (2- 7) 6.4 ( 2-16) 4.4 ( 2- 9)
Texas 2.3 (0-13) 19.3 ( 8-37) 10.1 ( 4-20)
Hortb Carolina 0 (0-14) 14.0 ( 5-29) 6.5 ( 2-18)
Combined study population 2.1 (0.5-5.5) 10.1 ( 5-17) 5.8 ( 4-10)
Hew York talc 6.8 (2-16) 18.6 (10-30) 12.3 ( 7-19)
Potash 5.4 (3- 7) 11.9 ( 9-15) 8.4 ( 6-11)
Underground coal 9.8 (9-11) 40.5 (39-43) 24.0 (23-25)
Aboveground coal 1.9 (0- 6) 28.0 (23-34) 13.9 (12-17)
Blue collar 4.7 (3- 7) 10.7 ( 8-15) 7.5 ( 6-10)
«*
ityspnea = Answering yes to the question: "Do you get short of
breath walking with other people of your own age on
level ground?"
SUMMARY:
<40: Montana «undergromd coal.
Combined study population «underground coal.
2^40: Montana «coal workers.
Texas and Morth Carolina «underground coal workers.
Combined study population «coal workers.
TOTAL: Montana «coal workers.
Texas and Borth Carolina «underground coal workers.
Combined study population «coal workers.
589
-------
TABLE 15. COMPARATIVE RATES OF BILATERAL PLEURAL THICKENING AMONG
TALC WORKERS COMPARED TO OTHER MINING POPULATIONS AND
BLUE COLLAR WORKERS. STRATIFIED BY AGE AND INDIRECTLY
ADJUSTED FOR SMOKING
Age
<40 >40 Total
% (95% C.I.) % (95% C.I.) % (95% C.I.)
Montana 1.1 (0- 5) 8.7 (3-19) 4.7 (2-10)
Texas 0 (0- 9) 16.4 (6-34) 7.8 (3-18)
North Carolina 9.8 (2-28) 10.9 (3-25) 10.3 (4-22)
Combined study population 1.5 (0- 5) 11.5 (6-20) 6.3 (3- 9)
New York talc 0 (0- 6) 16.6 (8-29) 7.9 (4-15)
Potash 0 (0- 1) 0.4 (0- 1) 0.2.(0-0.5)
Underground coal 0 (0-0.5) 0.1 (0-0.2) 0.1 (0-0.2)
Aboveground coal 0 (0- 3) 0.3 (0- 1) 0.1 (0-0.5)
Blue collar 0.4 (0- 1) 0.3 (0- 1) 0.4 (0- 1)
SUMMARY:
<40: North Carolina talc »all nontalc populations, except above-
ground coal.
>40: All talc populations »all nontalc populations.
TOTAL: All talc populations »all nontalc populations.
590
-------
The prevalence of phlegm was generally less in both age groups among the
study population compared to the aboveground coal workers. Overall the com-
bined study populations had less phlegm than all the comparison populations
except blue collar workers (Table 13).
The prevalence of dyspnea among the study population was less than under-
ground coal workers at all ages, and less than aboveground coal workers in the
older age group and when all ages were considered. There were no differences
in prevalence when compared to New York talc, potash, and blue collar workers;
in fact the frequency was generally lower in the study populations than all
of the comparison populations (Table 14).
In summary, the prevalence of cough, phlegm, and dyspnea was not elevated
in comparison to potash miners and blue collar workers, and after adjustment
for age and smoking.
Table 15 summarizes the comparative rates of bilateral pleural thickening.
Except for North Carolina where the prevalence of pleural thickening was 10
percent and higher than all nontalc populations, the rates were low in the
less than 40 years of age groups. In the 40 or greater year age groups the
prevalence of bilateral pleural thickening remained low (less than 1 percent)
in the nontalc comparison population, but was significantly higher in all the
talc populations, ranging from 9 percent in Montana to 17 percent in the New
York talc population. Overall adjusted rates in all the talc populations were
elevated compared to the nontalc comparison populations.
Pulmonary Function (Internal Comparisons)
Table 16 summarizes the results of multiple regression models of pulmo-
nary function with the predicator variables race, sex, age, height, smoking
status, region, department, years worked, and cumulative exposure. Age and
height were significant for all parameters (except for FEV percent). Race,
department, years worked, and cumulative exposure were not significant for any
of the lung function tests. Sex, smoking status, and region were significant
for some parameters. A multiple regression model without race and department
produced similar results although cumulative exposure achieves statistical
significance for FVC. Mean adjusted values by sex, smoking status, and region
are summarized in Table 17.
Pulmonary Function (External Comparisons)
Table 18 summarizes the mean percent predicted pulmonary function of the
study population compared to potash and coal (males only) and blue collar
workers (male and female). The study population of talc workers had reduced
FEVj, FVC, FEFso and FEF75 compared to both coal populations. Flow rates
(peak flow, FEFso» FEF7s) of the talc workers were reduced compared to the
potash and blue collar workers, but there were no differences in FEVi and FVC.
Regression models with observed/predicted lung function as dependent var-
iables and age, smoking status, region, department, and exposure as independent
variables were significant only for percent predicted FVC and FEFys. The study
population (Montana, Texas, and North Carolina combined) was estimated to show
591
-------
TABLE 16. SUMMARY OF MULTIPLE REGRESSION MODEL FOR LUNG FUNCTION OF ALL TALC WORKERS - REGRESSION MODEL:
PFT = a + 3i (race) + 3a (sex) + 3s (age) + 3«t (height) + 3s (smoking status) + 3e (region)
+3? (department) + 3a (years exposure) + 3s (cumulative exposure)
Age Height (cm) Smoking
Race Sex 3s (S.E.) 3 it (S.E.) status Region
FEVi% N.S. N.S. a N.S. a a
(%) -0.40 (0.04) -0.09 (0.07)
FEVi N.S. a a a b N.S.
(mL) -32 (3) +45 (6)
FVC N.S. a a a N.S. b
(mL) -19 (4) +64 (6)
Ol
VO
10 Peak flow N.S. a a a a N.S.
(mL/sec) -50 (9) +79 (15)
FEFso N.S. N.S. abb N.S.
(mL/sec) -61 (8) +29 (13)
FEF7s N.S. N.S. abb N.S.
(mL/sec) -40 (4) +12 (6)
Years
exposure
Department 3 e (S.E.)
Cumulative
exposure
39 (S.E.)
r
N.S. N.S. N.S. 0.60
-0.04 (0.08) +0.01 (0.02)
N.S. N.S.
-7 (6)
N.S. N.S.
-4 (7)
N.S. N.S.
+0.7 (17)
N.S. N.S.
-10 (15)
N.S. N.S.
-5 (6)
N.S.
-2 (2)
N.S.
-4 (2)
N.S.
-4 (4)
N.S.
+2 (3)
N.S.
-1 (2)
0.80
0.81
0.68
0.58
0.71
N.S. - p>0.05
a = p<0.01
b - p<0.05>0.01
-------
TABLE 17. LEAST SQUARES ADJUSTED PULMONARY FUNCTION MEANS OF TALC WORKERS BY SEX,
SMOKING STATUS, AND REGION, CALCULATED FROM MODEL:
PULMONARY FUNCTION * a + Si (sex) + &2 (age) + Ba (height) + 0i» (smoking status) + Bs (region)
+ Be (years worked) + B? (cumulative exposure)
vo
u>
FEV%
% (S.E.)
Male
Female
Smoking Status
Nonsmoker
Ex-smoker
Smoker
Region
Montana
Texas
North Carolina
78.1
80.0
80.4
79.6
77.2
76.8
79.9
80.5
(0.6)
(1.6)
(l.D
(1.2)
(1.0)
(0.7)
(1.3)
(1.3)
FEVi
L (S.E.)
3.85
3.35
3.71
3.58
3.51
3.58
3,51
3.71
(0.04)
(0.12)a
(0.08)
(0.09)
(0.07)
(0.06)
(0.10)
(0.10)
FVC
L (S.E.)
4.94
4.17
4.62
4.51
4.53
4.65
4.39
4.62
(0.05)
(O.l4)a
(0.09)
(0.10)
(0.08)
(0.06)
(0.11)
(0.11)
Peak flow
L (S.E.)
9.04
7.51
8.31
8.60
7.93
8.51
8.46
7.87
(0.12)
(0.34) a
(0.23)
(0.25)
(0.20)
(0.16)
(0.27)
(0.28)
FEFso
L (S.E.)
4.53
4.26
4.55
4.52
4.12
4.07
4.63
4.48
(0.10)
(0.29)
(0.19)
(0.21)
(0.17)
(0.13)
(0.23)
(0.24)
FEF?s
L (S.E.)'
1.55 (0.05)
1.41 (0.13)
1.63 (0.09)
1.44 (0.10)
1.37 (0.08)
1.41 (0.06)
1.48 (0.10)
1.55 (0.11)
FEV% = (FEVi/FVC) x 100.
95% C.I. do not overlap.
-------
TABLE 18. MEAN PERCENT PREDICTED PULMONARY FUNCTION OF MONTANA, TEXAS, NORTH CAROLINA TALC WORKERS
COMPARED TO MINER AND BLUE COLLAR COMPARISON GROUPS, ADJUSTED FOR AGE, HEIGHT AND SMOKING
% Predicted pulmonary function = (observed/predicted) x 100
FEVi FVC Peak flow FEF50 FEFys
Comparison Populations
Males Only (n - 251)
Potash 98.85 (1.01) 99.60 (0.84) 93.19 (1.03)a 95.62 (2.10)a 88.23 (3.12)a
Underground coal 97.55 (1.01)a 95.09 (0.80)a 100.19 (1.13) 95.62 (2.17)a 82.58 (2.75)a
Aboveground coal 96.60 (1.01)a 96.62 (0.83)a 112.43 (1.29)b 92.93 (2.00)a 80.76 (3.92)a
Males and Females (n = 292)
o, Blue collar 99.71 (0.95) 101.00 (0.78) 97.85 (1.04)a 94.12 (2.02)a 84.54 (2.41)'
VO
•JS
a » >2 S.E. less than 100, assuming no variation in prediction values.
b = >2 S.E. greater than 100, assuming no variation in prediction values.
-------
a reduction in FVC of about 0.25 percent less per year than the coal and potash
populations. Cumulative exposure had a statistically significant coefficient
of -0.07 percent (mg/m3 x years). Ex-smokers in the study population consistently
had reduced FVC compared to the aboveground coal and blue collar populations,
while all smoking categories were reduced compared to underground coal. Percent
predicted FVC was reduced in Texas when compared to all populations except
potash miners. Percent predicted FVC was reduced in Montana only when compared
to underground coal, and was reduced in North Carolina only when compared to
underground and aboveground coal workers.
Percent predicted FEF75 in the study population decreased about 2 percent
faster/year than the coal and potash populations, but increased about 1.5
percent for each year worked. Smoking, region, department and cumulative
exposure were not significant.
DISCUSSION
Interpretation of the data from this study has the inherent problems of
all cross-sectional prevalence studies. The workers examined in this study
comprise only those currently working. While there are few studies that have
examined ex-workers to determine the effect of selection, significant disease
has been observed among older ex-hemp workers7 and progressive massive fibrosis
among ex-workers in two silica flour mills.8 In both of these studies there
was significant disease among the currently employed workers. The consequences
of not examining ex-workers in this study are unknown.
The length of the study group's working history, however, is a relatively
short time for the development of occupationally related symptoms, radiographic
changes, and impaired lung function that might be caused by exposure to a
mineral dust. Significant changes in FEVi and FVC due to exposure to respir-
atory irritants (such as cigarette smoke) may not become noticeable until after
20 to 30 years of smoking. Essentially the same time interval may be required
for the development of pneumoconiosis.* The mean ages of the study populations
were around 40, and mean exposure to talc dust was less than 10 years. There-
fore, if talc dust were to adversely affect FEVj and FVC, the lung function
results might not reflect that effect because of the short exposure times
(unless the biological reactivity of talc and cigarette smoke is different).
Estimating past exposure was a problem in this as in other studies where
there was no historical environmental data. Although dust levels are assumed
not to have changed substantially with time, past expo.sure could be higher or
lower than the calculated estimates and obscure a true dose-response relation
if it existed. For example, if the estimates were higher than actual exposure,
a true association could be obscured because of fewer workers with "disease"
in the higher exposure group. If the estimate was lower than actual, an
association could be obscured because of more workers with "disease" in the
lower exposure groups. While years worked is an exact time period, it may be
a less accurate measure of overall exposure than the calculated estimate of
cumulative exposure. Oftentimes the two are confounded as three may be a high
correlation of years worked with exposure. This was not true for Texas but
there was an association of years worked and cumulative exposure in Montana
and North Carolina. Age is also generally correlated with exposure (years
595
-------
worked and cumulative exposure). In this study they were significantly cor-
related, except for age and cumulative exposure in Texas. Although statis-
tically significant, the correlations were not large. Thus for example, the
years worked sum of squares in the lung function regression models did not
change very much when adjusted for cumulative exposure and age.
Controls, or comparison populations, are always of concern. In this
report, two comparisons were utilized. One was an internal comparison, i.e.,
dose-response relationships, looking at the association of morbidity in
workers with high and low exposures within the study population. The second
compares the morbidity of the study population with the morbidity of the
control populations.
The advantages of the internal comparisons are that the variability from
measurement error, variability due to external factors such as season, dif-
ferences in the survey team, etc., are minimal. A disadvantage is that the
estimates of long-term exposures are not verifiable and may obscure a dose-
response relation. Also internal comparisons do not allow for an assessment
as to whether the prevalence of abnormalities are different than would be
expected if there were no work exposures.
For categorical parameters the groups were stratified by age and smoking
to look for effects of these potentially confounding variables before examining
their association with exposure variables. For continuous variables these
parameters were included in the regression equations. There was no consistent
association of increased symptoms, bilateral pleural thickening, or decreased
pulmonary function associated with either of the exposure variables. This lack
of a dose-response association is consistent with the finding of no differences
among the regions in the prevalence of symptoms despite the differences in
environmental dust levels. The differences among the regions in the prevalence
of bilateral pleural thickening were not large, and the tendency to increase
with exposure was somewhat confounded with the tendency for the prevalence to
also increase with age.
There was no association of dust levels or years worked with any of the
lung function parameters, except for FVC. There were no convincing regional
differences in lung function, although FVC was reduced in Texas compared to
both North Carolina and Montana. FVC was 0.23L and 0.26L less in Texas than
in North Carolina and Montana after adjustments for differences in sex, age,
height, smoking, and exposure. Without adjusting for exposure, the differences
in FVC were 0.60L and 0.61L for North Carolina and Montana respectively.
Thus the exposure adjustments reduced the regional FVC differences by about
60 percent. In Texas then, dust exposure was associated with a mean loss of
about 360 ml (or an average of about 67 ml/year). Reduction in FVC was dose
related in one model but not the other, and was estimated as -4 ml for each
unit of cumulative exposure. Multiplying the average cumulative exposure in
each region times the estimated loss in FVC for each cumulative exposure unit
shows that the calculated average loss in FVC resulting from talc dust expos-
ure was -23.6 ml in Montana, -45.2 ml in Texas, and -12 ml in North Carolina.
Maximum loss in each region was estimated to be -224 ml in Montana, -1496 ml
(1.5L) in Texas, and -84 ml in North Carolina. The biological significance of
these estimated mean losses are minimal except for the very high exposures in
Texas.
596
-------
The internal comparisons showed that age was consistently associated with
increased prevalence of cough, dyspnea, and decreased pulmonary function. The
calculated loss of pulmonary function with age was comparable to values from
other cross-sectional studies1*»12 and there was little difference in the age
coefficients among the regions. The relationship between smoking and pulmo-
nary function was as might be expected. Smokers generally had the poorest
values, and nonsmokers the best.
The second way to attempt to control for confounding variables and to
estimate whether there is elevated morbidity is to compare the study population
with some other population or populations. The ideal (which is never achieved)
is to compare the study population with another population that is identical
in every respect except exposure. Since in this study local comparison popu-
lations were not available, workers examined by NIOSH in other studies were
used for comparison. The comparison populations were examined using the same
basic protocol so that measurement error is probably reduced. Each population
has certain advantages and certain disadvantages; for example, the coal and
potash workers are miners, but are not unexposed. The blue collar workers are
a population thought to be unexposed to respiratory irritants, but they are
not miners.
There are several reasons for using multiple comparison populations. No
comparison population is ideal, and several may help in interpretation of the
data. Several factors may affect comparative morbidity that are not related
to work exposure; but are not measured. They include region, socioeconomic
status, type of employment (for example, mining), weather, season, technician,
etc. It is not likely that several comparison populations will all have
biases in the same direction relative to the study population. Thus consis-
tent differences between the study and comparison populations gives one more
confidence that the differences are not the result of unknown or unmeasured
variables.
There was little difference in the prevalence of cough, phlegm, and
dyspnea among the talc study population, potash miners, aboveground miners,
and blue collar workers. (Older aboveground coal workers had an elevated
prevalence of dyspnea.) New York talc workers and underground coal miners
consistently had elevated symptoms rates. Predicted FEVj and FVC was reduced
2 to 5 percent below predicted when compared to the two coal mining populations,
and after adjustments for age, height, and smoking. Interestingly, FEVj and
FVC of the study population were not reduced compared to potash miners, or
blue collar workers; neither of which is believed to have occupational expos-
ures known to reduce lung function. As neither exposure variable was signif-
icant, it seems unlikely that exposure was causing the differences in lung
function between the study and comparison populations. Although statistically
significant, the mean differences in adjusted FEVj and FVC between the study
and coal populations were not large. Substantial reductions in FEVj and FVC
are of concern because several studies have shown them to be related to risk
of death (although not necessarily death from respiratory disease) (Becklake
and Permutt, 1979), but the small reductions in FEVi and FVC seen in this
study are not of the magnitude to cause this type of concern. This conclusion
must be qualified because of the short exposure time, however.
597
-------
Flow rates at low lung volumes (FEFso and FEF75) in the study population
were less than 100 when compared to other miners and blue collar workers.
FEFtQ was better than 90 percent of predicted, while FEFys was between 80 and
90 percent. Air flow at low lung volumes is considered to be measuring changes
occurring primarily in the small airways (Hyatt, et al., 1979; Mead, 1979).
A current hypothesis of the pathophysiology of chronic air flow obstruction is
that changes in lung function seen in disease such as emphysema start in the
region of the small airways.Au>15 Tests such as FEF5Q and FEF75 are of
interest because it is difficult to detect pathophysiologic changes in the
small airways that may be occurring for unknown time periods before they
become evident in more routine tests such as FEVj and FVC. While existing
data (such as the ability of FEF50 and FEF75 to detect differences in high and
low risk groups) are compatible with the idea that air flow obstruction begins
in the small airways, there are no available prospective data to prove it.
Therefore, the significance of these reductions is only suggestive.
Peak flow was reduced in the study population compared to potash and blue
collar workers, was no different than underground coal miners, and was elevated
compared to aboveground and coal workers. Peak flows are roost sensitive to
changes in large airways, but are also most subject to technician differences
and subject effort. The prognostic significance of reduced peak flow is also
not known.
The most surprising finding in this study was the prevalence of pleural
thickening. Asbestos (particularly anthophyllite) from either occupational or
community exposure is associated with an increased prevalence of pleural
thickening.10 Talc contaminated with asbestos (tremolite and anthophyllite)
seen under the light and electron microscope has also been associated with an
increased prevalence of pleural thickening. But studies of workers exposed
to talc without significant asbestos content have reported radiographic changes
characteristic of pneumoconiosis,17>18»19 rather than pleural abnormalities,
and excessive mortality from nonmalignant respiratory disease (supported by
radiographic evidence).33 The prevalence of pneumoconiosis, however, was not
significant in this study. Pleural abnormalities (unspecified) were found in
9 percent of Vermont talc workers compared to 9 percent with small irregular
opacities and 12 percent with small rounded opacities. This is in contrast to
this study where pleural thickening was observed in 9 percent of the population,
but less than 1 percent had pneumoconiosis.
Pleural thickening due to asbestos exposure is generally considered to
take many years to develop. In a study of a Swedish population, mean latency
for the development of bilateral pleural plaques after first exposure to
asbestos was estimated at about 30 years and pleural plaques were rare before
age 40. 21 However, Ochs and Smith22 reported on at least one case where as
little a time interval as one year was necessary for the appearance of bilat-
eral pleural thickening in an individual without occupational asbestos expos-
ure. In the study reported here, latency (time between first known talc
exposure and date of the study) was 13 years for workers with bilateral
pleural thickening and 4.5 years in those with unilateral thickening, a much
shorter time than generally associated with asbestos exposure.
598
-------
The prevalence of pleural thickening may vary considerably. In a Swedish
study about 1 percent of the men over 40 and less than 0.1 percent in men less
than 40 had bilateral pleural plaques.21 Almost 80 percent were current or
ex-smokers and had had some exposure to asbestos. Fibrosis was rare (4 percent
of those with pleural thickening). Another community type study in Birmingham,
England23 found that about 7 percent of those attending chest clinics had
pleural plaques (10 percent of these were calcified). Unilateral obliteration
of the costophrenic angle (not considered to be caused .by asbestos) was ob-
served in 36 percent of those with pleural plaques, and there was a definite
history of asbestos exposure in no more than 11 percent of the cases. Much
of the pleural thickening was considered to be due to pleural disease (39
percent of those with pleural abnormality reported having had emphysema,
several chest wall injuries, two or more attacks of pleurisy, compared to
12 percent of the controls). Single attacks of pleurisy were considered as
having only a slight likelihood of producing pleural thickening. In the study
of talc workers reported here there was no obvious difference between those
with and without pleural thickening in the exposure to asbestos or in chest
disease.
In these two community studies, the association of pleural thickening was
quite different, and was not necessarily related to asbestos exposure. The
association with pleural thickening may in fact be incidental as the prevalence
of pleural thickening may be quite different in asbestos exposed workers. For
example, prevalences of 17.5 percent and 35 percent have been reported in
asbestos manufacturing plants and shipyard joiners.214'25 Two other studies of
shipyard and dockyard workers reported prevalence of pleural thickening around
5 percent.21*'26 It is possible that factors other than asbestos (both the
type and magnitude of exposure) may account for these differences (e.g., age
distribution; method of reading X-rays, oblique X-rays in addition to PA;
incidence of tuberculosis; bacterial or viral infections; smoking habits).
Exposure to other dusts may also be associated with pleural abnormalities.
Smith27 reported finding pleural calcification among 1.5 percent of 197 bake-
lite insulators, 1.7 percent of 114 calcimine workers, 1.6 percent of 302 men
making mica insulators, and 6.3 percent of miners and millers exposed to
tremolitic talc, but none in 261 asbestos workers. Smith27 comments that the
common feature of exposure of all four groups with pleural calcification was
exposure to talc and/or mica. Thus while pleural thickening is said to be a
signpost of asbestos exposure,*6 other agents have been associated with pleural
thickening in the absence of known asbestos exposure. Because no asbestos was
found nor thought to be associated with Montana and North Carolina talc, these
results suggest that talc itself may be capable of causing the pleural changes.
It is also possible that there are pockets of asbestos in the talc deposits,
that could result in asbestos exposure sufficient to produce pleural changes.
We do not have available a detailed clinical history to evaluate the
possibility of chest injury or disease producing the pleural thickening in
these populations. If such conditions were causative, they would be more
likely to produce unilateral rather than bilateral thickening. We have
therefore looked at the association of exposure with bilateral pleural thick-
ening which is more likely than unilateral to be occupational in origin.
599
-------
When we do so, the association with talc exposure remains. And in the popu-
lations over 40 there was no statistical difference in the prevalence of
bilateral pleural thickening irrespective of the purity of the talc. It is
possible that there was a difference in the radiographic interpretation
(different reader, calendar year, weight difference in those with and without
pleural thickening). Evaluation of this potential bias is currently under
investigation. Until that study is completed, the most likely explanation
for the increased prevalence of pleural thickening is the exposure to talc.
The clinical significance of pleural thickening, pleural plaques, and
pleural calcification as a result of asbestos exposure remains unclear, but
is of concern because the pleural changes are considered to represent a sig-
nificant exposure to asbestos and may be related to mesothelioma. The sug-
gestion28 that talc is possibly carcinogenic may be due to asbestos contam-
ination of the talc. The characteristics of talc have mostly been poorly
reported. Talc free of asbestos contamination does not appear to Increase
the risk of cancer, and mesothelioma has not been associated with talc
exposure.2^»30>^*' Risk of cancer in this study cannot be determined.
Although lung function is somewhat reduced in those with bilateral pleural
thickening, the biological significance of pleural changes in the talc popu-
lations of this study is also unclear.
CONCLUSIONS
In this cross-sectional study of 299 talc workers from Montana, Texas,
and North Carolina, there was no association of symptoms (cough, phlegm,
dyspnea) or reduced lung function with exposure. The prevalence of symptoms
was not elevated and there was no difference in FEV^ and FVC compared to the
potash and blue collar control populations. Minimal (but statistically sig-
nificant) reductions occurred in comparison with coal workers. Thus both
internal and external comparisons were generally consistent in confirming the
lack of an association between exposure and morbidity. While there were no
differences in the symptom prevalences among the three talc regions (despite
differences in exposure and talc composition), there were differences in the
prevalence of cough and phlegm between the study population and the workers
exposed to talc containing tremolite and anthophyllite.
The major significant health effect observed in this study was the
increased prevalence of bilateral pleural thickening. The excess was con-
siderable in relation to the nontalc comparison populations, but the dose-
response relationships were somewhat confounded with age. The similar results
with the New York talc population, the lack of a consistent association of
pleural thickening with asbestos exposure, and the lack of parenchymal changes
in the talc exposed workers suggest the possibility that talc was an etiologi-
cal agent in the development of bilateral pleural thickening. The long term
significance is unclear. While those with bilateral pleural thickening had
some reduction in lung function and a possible increase in symptoms, the
clinical effects were mild. The concern as to whether pleural thickening is
a precursor of mesothelioma remains unanswered. This would appear unlikely
because of no reported mesotheliomas associated with talc exposure.
600
-------
Several points seem relevant to interpreting the results. The exposure
times are relatively short. Therefore-more time may be needed to see exposure
effects. The reduced flow rates of low lung volumes supports this caution, as
they may be early indicators of airways disease. On the other hand, the
association of talc exposure with bilateral pleural thickening is occurring
after shorter latency periods than is commonly found among asbestos workers
and is associated with some loss in lung function, but no apparent disability.
A prospective study seems necessary to answer the question concerning long
term effects of exposure to talc, and the prognostic significance of pleural
thickening.
601
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INDUSTRIAL HYGIENE PORTION
INTRODUCTION
Talc, a magnesium silicate mineral, is mined in several geographic areas
in the United States. The ore bodies examined in this study were Montana,
Texas, and North Carolina. We examined seven mines and eight mills.
The purpose of the study was to characterize the talc, evaluate the
workers' exposure, and ascertain the chronic effects of exposure (Table 19).
The environment of each facility was characterized as to total and respirable
dust concentrations, percent free silica, trace element concentrations,
percent fibrous minerals, calcite, and dolomite. Individual exposure was
determined by personal respirable breathing zone samples on all participating
employees. Estimates of exposure for each job were obtained from the personal
samples.
TABLE 19. INDUSTRIAL HYGIENE CHARACTERIZATION OF TALC
I. Personal Respirable Breathing Zone Samples
II. Trace Element Concentration
III. Mineral Composition
IV. Fibrous Minerals
V. Free Silica
The mines in Montana and Texas are typical open-pit operations, while the
mine examined in North Carolina is underground employing square set timbers
and stopes.
RESULTS
Personal respirable breathing zone samples (PRBZ) were collected from
each participating employee and time weighted averages (TWA) were obtained.
The TWA's were utilized to derive geometric mean values for each job examined.
These mean values were then used to develop cumulative exposures.
The time weighted averages for each employee were grouped together
according to the actual job performed on the day of the study. The geometric
mean for each job classification was then calculated from the grouped TWAs.
The geometric mean for the dust levels in the mine and mill are presented
by region (Table 20 and 21).
Each ore body was analyzed for the following trace elements: Iron,
manganese, calcium, aluminum, zinc, and nickel (Table 22). These trace
elements were selected to compare the talc examined in this study with the
talc examined in New York and Vermont.
602
-------
TABLE 20. PERSONAL RESPIRABLE BREATHING ZONE SAMPLES
(AVG - GEOMETRIC MEAN)
Job
Montana
Bagger
Labman
Fork Lift Op.
Mill Operator
Laborer
Foreman
Boiler Operator
Front-End Op.
Maintenance
Welder
Wash Plant Op.
Sorter
Driller
Truck Driver
Miner
Shovel Operator
Calciner Operator
Avg 3
(mg/m )
2.8
.3
.5
1.0
1.4
.6
.1
.8
.4
6.3
1.4
1.6
.1
.3
.4
.2
.6
Variance
1.9
2.5
1.8
2.5
2.0
2.8
4.9
6.1
4.3
8.7
2.3
1.8
1.9
3.6
—
Number of
Samples
29
4
5
7
6
14
2
14
16
1
2
50
1
15
2
5
1
.86
Texas
.59
174
'Bagger
Stacker
Forklift Op.
Mill Operator
Laborer
Foreman
Front-End Op.
Maintenance
Sorter
Driller
3.1
1.6
2.3
38.4
1.3
1.3
1.3
1.0
.6
.7
2.9
—
1.5
4.5
3.6
5.3
3.6
1.8
2.0
3
1
2
1
10
4
7
10
2
2
(continued)
603
-------
TABLE 20 (continued)
Job
Texas
Truck Driver
Miner
Shovel Operator
Calciner Operator
Crusher Operator
Welder
North Carolina
Bagger
Mill Operator
Laborer
Foreman
Maintenance
Driller
Hoist Operator
Miner
Grader
Packer
Cutter
Rounder
Officer Personnel
ALL REGIONS
Avg 3
(mg/m )
.9
.1
.3
1.1
1.7
8.5
TTos
.9
.9
.2
.9
.03
.1
.1 '
.3
.4
1.2
1.2
.9
.1
"721
.72
Variance
1.5
1.5
1.2
___
—
T52
___
— —
5.8
5.8
1.4
2.2
4.2
4.8
2.5
16.5
T74
.68
Number of
Samples
5
2
2
1
I
1
54"
1
1
9
1
2
3
2
9
7
1
4
1
3
44~
275
604
-------
TABLE 21. SUMMARY OF RESPIRABLE DUST SAMPLES
(AVG - GEOMETRIC MEAN)
2
Region Avg (mg/m )
Montana
Mill 1.1
Mine .66
Texas
Mill 1.56
Mine .45
North Carolina
Mill .26
Mine .14
CONCLUSIONS
95% Confidence
Range of Mean
.85 - 1.41
.47 - .92
2.54 - .96
.18 - .71
.13 - .51
.07 - .31
Mill - Baggers and Mill Operators had highest exposures.
Mine - Truck Drivers and Front-end Loader Operators had highest exposure.
605
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TABLE 22. TRACE METALS (mg/m3)
Montana
Iron
.05
Manganese
Calcium
.05
Aluminum
.2
Zinc
£.01
Nickel
£.01
.01
,01
Limit of Detection
.03 .1
.01
.01
North Carolina
Iron
.05
Manganese
£.02
Calcium
.05
Aluminum
.2
Zinc
£.02
Nickel
£.02
.02
.02
Limits of Detection
.02 .04
.02
.02
Texas
Iron
.5
Manganese
£.08
Calcium
8.0
Aluminum
.04
Zinc
.08
Nickel
£.08
.08
Limits of Detection
.2 .2
.08
.08
606
-------
Montana talc had the lowest concentrations of trace elements of the
three regions examined. The trace element concentrations were slightly higher
in North Carolina. Texas talc differed most significantly from the other
regions by its extremely large concentration of calcium.
The mineral composition of bulk samples also indicated higher calcium
value in Texas. This talc had a much larger percentage of dolomite
and a slightly larger percentage of calcite (CaC03) than the other two regions
(Table 23).
TABLE 23. MINERAL COMPOSITION OF BULK SAMPLES, AVERAGE
PERCENTAGE (RANGE IN PARENTHESIS)
Calcite Dolomite
Montana 41 1
(0-0.8) (0-3)
Texas 1 13
(0-3) (7-20)
North Carolina 0 3
0 (1-4)
Examination of bulk samples of talc from each region for free silica
demonstrated the same trend as other contaminants (Table 24). Montana talc
had <0.8 percent, which was the limit of detection. North Carolina had a
slightly higher percentage, while Texas had the highest observed silica
content.
TABLE 24. FREE SILICA BULK SAMPLES
Montana /.0.8% (Limit of Detection)
Texas 2.23%
North Carolina 1.45%
Respirable dust samples revealed the silica content in Montana and North
Carolina to be generally below the limit of detection. The Texas talc had
slightly higher levels of respirable silica.
Analysis for the presence of fibrous minerals was two-fold. The first
analysis was with light microscopy utilizing phase contrast techniques. Light
microscopy was used as a screening tool to detect the presence of fibers.
Further analysis of samples from each region was performed utilizing analyti-
cal transmission electron microscopy (Table 25). Fibrous minerals were not
detected in any samples of Montana talc.
607
-------
TABLE 25. FIBROUS MINERALS
Montana
None Detected
Texas
Tremolite
Antigorite
North Carolina
Acicular Particles
There were two fibrous minerals identified in the Texas talc: tremolite
and antigorite.
Antigorite, a serpentine mineral, was the major constituent. The fibers
of both minerals ranged from 0.5 to 3.0 ym in diameter and 4 to 30 ym in
length.
The morphology of the North Carolina talc was identified as acicular.
The acicular particles had aspect ratios ranging from 5 to 1 to 100 to 1 with some
diameters <0.1 ym. The acicular particles may have resulted from mechanical
destruction of plates.
Other data concerning the composition of the talc from these facilities
is being investigated and will be reported elsewhere.
608
-------
ACKNOWLEDGMENTS
We appreciate the assistance and cooperation of the companies and workers
which made the study possible. We thank the ALOSH medical fi«»1d team and
interpreters who helped collect the data, and Mary, who typed the many drafts.
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611
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ROUNDTABLE DISCUSSION ON TALC
QUESTION (Dr. Cooper): How does one measure pleural thickening?
ANSWER (Dr. Langer): Pleural thickening is estimated by visual inspection
of a chest x-ray. Using a specific classification for abnormal
findings, one gauges the thickness and extent of the pleural lesion.
The details may be explained by Dr. Lewinson who is here. Hilton
do you want to add to this?
REMARK (Dr. Lewinson): The explanation is fine.
QUESTION (Mr. Ashton): I am from Johnson and Johnson. I ask for those of
us who are not medically oriented; exactly what is pleural
thickening?
ANSWER (Dr. Langer): Pleural thickening has been described as an abnormal
increase in the thickness of the pleura (the linings of the chest
wall and the lung) brought about by the development of scar tissue.
This is the result of exposure to fibrous dust. It is mainly con-
fined to inorganic mineral fiber insult although it has now been
observed in fibrous glass workers as well. It means a fiber has
penetrated the alveolar space, migrated to and lodged in the pleural
tissue, and has initiated some scar response.
Dr. Gamble has suggested that pleural plaques, hyalinized thickened
pleura, might be a prognostic indicator of mesothelioma since it is
the same damaged tissue substrate from which the mesothelioma
originates. This was suggested in some work of John Edge. He
observed that within a select population of shipyard workers in
Great Britain, men with pleural plaques developed mesothelioma
more frequently than men without plaques. But the caveat raised in
criticism to this hypothesis stated that men who had pleural plaques
tended to be the oldest workers. The oldest workers also translated
into men with greatest latency period since onset of exposure.
Increased occurrence of mesothelioma would be expected in this group
of asbestos-exposed workers. Those workers who do not develop
asbestosis and die, those who do not develop lung cancers and die,
are those who are candidates for mesothelioma. This is part of
competitive risk. Edge's most recent paper (in the recent New York
Academy of Science Asbestos Conference Meeting) indicates that the
"plaque population" was "select" and the occurrence of pleural
plaque may not be a prognosticator of more severe .diseases to come.
REMARK (Dr. Lewinson): I think the question of whether pleural thickening
or pleural plaques are a prognostic sign and whether they indicate
that these people are of greater risk of developing mesothelioma is
one which has not been resolved.
612
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REMARK
QUESTION
REMARK
ANSWER
QUESTION
ANSWER
QUESTION
ANSWER
I think, however, to add to what you have said, you should bear in
mind that anthophyllite experience in Finland: pleural plaques are
extremely prevalent there, yet mesotheliomas have not occurred.
(Dr. Langer): That is absolutely correct. Mesothelioma has not
been reported amongst the Finnish anthophyllite workers. Yet,
pleural plaques are observed.
(Mr. Clifton): I am from the U.S. Bureau of Mines. I notice that
all of the exposure levels shown here tonight were given in mass
units. This is quite confusing. We used mass units previously
and then we had to go to fiber number. Now we are going back to
mass units. How much of what were these people exposed to?
(Dr. Langer): I am going to leave that to our industrial hygienist.
I think the question refers to the nature of the phases in a talc
environmental sample. Total particulate mass says little.
(Ms. Grief e): All of the data we collected were in milligrams. We
did no impinger sampling. In New York, let me stand to be corrected,
they did both cyclone sampling (which would give you milligrams
per cubic meter) as well as the impinger sampling (which would give
you million particles per cubic feet).
(Mr. Clifton): You have not answered my question. I asked how
much of what. How much fiber, how much talc?—What are the actual
mineral phases and their form? You just gave us "milligrams". I
do not know what "milligrams" represent, fibers, or otherwise.
(Ms. Griefe): The respirable samples measured the total respirable
dust in the air. There was no definition of the particulates on
the filters whether, for example, half were fibers or half of it
was talc. The cyclone samples, you are quite correct, measure
what is in the air. The other airborne samples, for example,
measure how many fibers, if there were fibers present.
(Mr. Clifton): All you are saying then is that all you measured
was "dust" in the air?
(Ms. Griefe):
correct.
On the cyclone samples, the personal samples;
REMARK (Mr. Clifton): Well, the "dust" in the air does not tell us any-
thing about the actual exposure.
QUESTION (Chairman Rowe): Mr. Clifton, what would you expect to find in a
grinding mill that was grinding talc except talc dust?
ANSWER (Mr. Clifton): What I am saying is that if I am going to be regu-
lated under the asbestos regulations I would expect field
inspectors to count asbestos fibers, not talc fibers.
613
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REMARK (Chairman Row*)! Ma. Griefe haa already told you that thara wara
not any fibara In it,
ANSWER (Ma, Griefo)« Mr, Clifton, if I may clarify parhapa for thoaa who
do not undaratand, Tha figure* that wa gava for the duat concan-
trationa wara paraonal raaplrabla braathing aona aamplaa which
wara cyclona valuaa which givaa maaa, Wa countad fibara on airborna
aamplaa if fibara wara praaant. If fibara wara not praaant, of
couraa, wa did not count tham,
REMARK (Mr. Clifton): You did not indioata thia in your praaantatlon.
REMARK (Ma. Qriafa)i That ia trua.
QUESTION (Dr. Langar)t Dr. Gambia, you hava baan aakad if tha talc duat wara
to ba a fibroua duat how might thia influanca aoma of tha data that
wara praaantad thia avaning?
ANSWER (Dr. Oambla)i Wall, I guaaa tha cloaaat data that I hava would ba
tha Naw York talc, In tha oompariaon that wa did, wa aaw no
diffaranca in tha aymptoma of coughj tha pravalanca of phlagm waa
highar in tha Naw York talc; thara waa no diffaranca in ahortnaaa of
braath or in bilataral plaural thickaning,
QUESTION (Mr. Schmltt)i I am from tha Flintkota Company. I would Ilka to
aak aavaral quaatlona which ara not apacific to tha talc aubjact
that wa juat diaouaaad. Thay ara ralatad to aoma of tha othar
atudiaa which wara mantlonad thia aftarnoon and which I auapact wa
will haar mora of tomorrow, All of thaaa ralata to fibroua
matariala which I prafar not to call aubatitutaa bacauaa thay hava
baan around aa long, or If not, longar than aabaatoa. So, lat ua
aliminata tha word aubatltuta. Wa ara daaling with fibroua matariala
which may or may not bacoma mora pravalant in tha workplace,
My quaationa ralata to thaaa madical axpoaura atudiaa, ralating
axpoaura to human health affacta, T gat tha impraaaion that
qulta a number of thaaa "othar materiala" ara not qulta aa harmful
aa aabaatoa flbar. Tha quaationa that I hava in my mind arei How
do tha amallar axpoauraa affact tha praaant atudiaa? What affact
doaa tha ahortar latancy period hava on thaaa atudiaa? If wa wara
to compare thaaa atudiaa to tha early aabaatoa atudiaa, and I will
pick 1954 aa a particular yaar whan thara waa conaidarable doubt
about tha harmful affacta of aabaatoa fiber, are we in a "too early
to tall" pariod? Wa are hearing tha aama kind of dlaputa going on
among tha madical fraternity on whether or not thaaa axpoauraa ara
harmful or not and to what degree thay may or may not ba harmful and
we even gat involved in high level atatlatical dlacuaaiona and
theory, If wa ware to repeat thaaa atudiaa 20 yeara from now what
aort of verdict would we receive on aome of thaaa "othar fibroua
matariala?", I will poaa the queation to you, Doctor Langar, and I
will lat you put it wherever you want It,
614
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ANSWER (Dr. Langer)i The MO are th« underlying great questions. That: I-i
That which we uau as a substitute today, huw sale in it really?
What kind of data do we have? How long have we been studying the
matarlal? Is It long enough lor observing Hinical effects? And
MO on. You are right. It may take another period ol 25 or 35
years before we find out that the substitute thai was used today,
put Into some product with a hope of reducing health rlek, hae
actually created a whole new "Pandora 'a box" of problem*. Obviously
this lw the key to all the laeuee and diecusslons,
You may think that In 1954 we did not know very much about
asbestos; yet II you read the literature you can go back further In
time and dlacover that investigators were talking about asbestos
and cancers many years before 1954. There were many signs that
Indicated that asbestos had great biological potential. Can we
extrapolate these past experiences with the present? Perhaps.
For example, there exists a range of materials we call talc.
may repreaent a wide range of substances because as used In the
Industrial setting may Include Impure talc materials, ur may be
very pure taJc. It could be the New York State talc or It could
be the Montana talc. These are two extremes. For the New York
State talc, there are data which Indicate that Inhalation produces
significant disease, We have no similar data for Montana.
Workers who work In New York State talc deposits develop talcoais,
(bilateral Interstitial lung scarring): they develop pleura!
plaques: they develop what appear to be asbestos bodies in their
lung tissues; they develop lung cancers in excess at the antlrl
pated amounts In the smoking-matched populations: they develop
meeothelloma. Here the evidence Is in. What about platy talc?
Should you wlah to wait another 30 years? Per hap « the materials
that we are dealing with in the pure form are less biologically
active. These produce lung scarring In laboratory animals. There
are reports that pure talc produce! talcoeis in humane. Yet no
data exist! Indicating excess cancers. Do these data sets mean
that the active agents are the liber contaminant! and not the talc
itself? Should we consider platy talc as a flbrogenlc Agent only
and fibrous talc as both a flbrogenlc and a carcinogenic agent?
Limited data luggest this, The human studies by the Morgantown
group Involve small numbers of people. It la a very young popu-
lation, These are people who Just got into the study. If major
clinical findings were found 1 would be aghast. With these
groups we must have more time to observe them and determine if
health effects are produced. I think we are going to have to wait
a long time before we find out. The bottom line is this: some
limited human data, some animal studies, some in vitro testing may
point the way to a dangerous substance without waiting tor the last
case of pneumoconlosis to occur in a followed human population.
615
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QUESTION (Mr. Mill): I am from Cabot Corporation. I would like to ask a
question that may be germane to what you just said. Throughout
this meeting we have heard a great deal about the geometry of the
particles that cause health problems. We have heard very little
or actually nothing about the surface chemistry. We know that
certain related materials may stabilize free radicals on their
surface. We know that material such as chrysotile can have a great
amount of elemental substitution and therefore the surface chemistry
can change a great deal. Has anyone made measurements of the
surface chemistry of fibers and related them to some of the measured
biological activity? Or have people merely tried to take the
geometry and relate it to health effects?
ANSWER (Dr. Langer): I agree with you that surface is critical. Geometry
is one of the factors which relates to aerosol stability; to
inhalation potential; to penetration of particles to the alveolar
space; to migration to the pleural surface. It is the geometric
factor which controls how much dust gets into the lung and to which
target tissues. It may also control ability of alveolar macrophages
to ingest fibrous dusts (primarily length). But once it is in the
lung, once it is at the target tissue, other factors come into play.
These I believe, as you do, are the surface properties. When you
talk about the stabilization of free radicals, we have noted that
the grinding of chrysotile, which alters its surface, reduces the
ability of the mineral to reduce diphenylpicryl hydrazyl to the
hydrazine phase at its surface. Its membrane activity character-
istics change also as do many other properties. When we talk about
fibers we are talking only about inhalation potential; but when we
talk about surface properties, we are talking about mechamisms.
Lets back up for a minute. Lets talk about morphology and its
relation to other important physical properties. Thin fiber means
more fiber per unit mass of substance. Fiber number, reflects
surface area. Surface area reflects bond number available on the
surface. Some people think the electron migration on mineral
surfaces, and their ability to interact with various compounds, is
important. So do I. There has been much work from the Germans in
this area. We have some work in our laboratory as well. Proton
migration, hydroxyl release, trace metals, oxygen-silanol bi-
functionality, geometric considerations, stereospecificity of
surfaces for biological molecular moieties, etc., are but a few
surface interactions possible.
We have been able to take a simple mineral like quartz and demon-
strate its complex surface character. For example, we have taken
quartz, size-fractionated quartz specimens, with different trace
metal populations, measured the zeta potential (more or less a
surface charge measurement) and observed vastly different membrane
activities. Some are very potently hemolytic and others not. It
is well known in the European literature that workers exposed to
silica from iron mines, and those that are exposed to free silica
in the presence of aluminum, have less silicosis. As a matter of
fact the Germans had aluminum inhalation therapy for workers exposed
to silica dust.
616
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QUESTION
ANSWER
QUESTION
ANSWER
REMARK
ANSWER
REMARK
REMARK
REMARK
What we are saying Is that you can take a single mineral sub-
stance, with different trace metals, ground in different ways, and
produce vastly different biological potentials. It is truly
simplistic to think that a fiber, because it is a fiber, produces
disease. Biological activity must be surface related.
(Mr. Mill): If you take chrysotile and you have a certain
activity can you take a ceramic fiber made by XYZ Corporation and
get the same activity?
(Dr. Langer): No, I would not expect that.
(Mr. Mill): Not at all?
(Dr. Langer): Even if that fiber were to have the same dimension-
ality. Let us say you were to make a ceramic aluminum silicate
fiber to put into a cigar and you were to make it of the dimension-
ality of 350 angstroms. You would have the same number of fibers,
the same mass delivered to the target, the same surface area, the
same particle number, the same hits per unit cell. Will it elicit
the same response? I do not believe it for an instant.
(Mr. Mill): So what you are really saying is that because of the
surface chemistry measurements it is very likely that something like
a ceramic fiber would not be active.
(Dr. Langer): I did not say that.
different responses.
I said that they produce vastly
(Mr. Mill): This might be a way of shortening the 20 years required
for human studies. Animal studies are very important.
(Dr. Langer): I agree. What you are talking about now are
mechanisms too, not just effects. If you are going to consider
asbestos substitutes you should not introduce this material to the
workplace and then wait 25 or 35 years to find out whether or not
it is going to kill someone. You might do some animal studies, or
even some in vitro tests, to determine membrane activity, protease
induction or whatever. I agree with you, activity is a function
of the surface characteristics of the material and not just the
fact that it gets in there. Different minerals have different
activities.
(Dr. Flowers): A comment on the surface chemistry. There has been
some recent work regarding the reduction of biological activity
of asbestos through the modification of its surface. There were
two patents issued to Dow Chemical in October of 1979 which
Involved the modification of the surface of asbestos by coating the
fiber with various metal salts. These essentially block the
magnesium oxide-hydroxide sites. These preparations have been shown
617
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to reduce hemolytic activity, membrane effects, release of
enzymes and general cytotoxicity. Tomorrow I will be presenting
my talk about chemical detoxification of asbestos. There has been
some agreement voiced that the geometry determines the site of
deposition and surface chemistry determines biological effects.
At least that is the premise.
QUESTION (Mr. Slovik) : I am with the U.S. Bureau of Mines. I noticed on
several of the slides that the samples were divided between non-
smokers and ex-smokers, and smokers. What was the criteria to
determine an ex-smoker versus a nonsmoker and did the data vary with
the length of time away from the cigarettes?
ANSWER (Dr. Gamble): We did not look at the length of time away from
cigarettes. It was just simply if they had never smoked, they
were a nonsmoker; if they had stopped smoking but had once smoked,
they were classified as an ex-smoker. We did not really look at how
much they had smoked or how long. It is just a simple categorization
of those three groups.
QUESTION (Dr. Reeves): I have to come back to the question I asked earlier.
Maybe I ought to address this to Doctor Langer. Did you know that
the AC6IH (American Conference of Governmental Industrial Hygienists)
lists "fibrous talc" with the same TLV value as crocidolite or
anthophyllite? Under presently available evidence is this justified
or is it not?
QUESTION (Dr. Langer): It has the same TLV as crocidolite?
ANSWER (Dr. Reeves): Yes.
ANSWER (Dr. Langer): I have often said that crocidolite is a more active
fiber for producing mesotheliomas than most other mineral fibers.
I believe this to be so on the basis of its geometry, the amount of
fiber dose delivered to target cells. Crocidolite breaks down into
extraordinarily small fibers. Crocidolite produces great numbers
of mesotheliomas. Let us use that as a positive index. The
question then is: should fibrous talc, true talc fiber, have the
same TLV? I think this is a bit overextrapolated. They have very
different biological activities, and different biological effects.
QUESTION (Dr. Reeves): Should it even have the same TLV as anthophyllite?
ANSWER (Dr. Langer): Let us take a different track. Suppose I were head-
ing OSHA or MSHA, and it was my responsibility to protect workers.
Suppose I had no data. Suppose the only data I had was morphology.
If I read Pott's work, and the work in Europe which suggests that
something which has a fibrous shape is active, a potent carcinogen,
or Merle Stanton's work here in the United States which suggests
the same, I would say "okay, let's have every fibrous mineral that
is being mined come under the same TLV". If I had more data and
618
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Information I would think that these should have different TLV's.
But you know this is extraordinarily complicated. What if we
were to do the following: what if every mineral fiber were to
have its own TLV? What would we do in the case of the New York
talc deposit? We would monitor for tremolite; we would monitor for
anthophyllite; we would monitor for fibrous talc. We would have to
distinguish among those phases. You cannot do this by phase con-
trast microscopy. We would have to count silica particles
separately; the tirodite fibers, then hexagonite fibers; and so on.
Xt is an extraordinarily difficult situation. Do we lower all of
the TLV's or do we raise them all? Do we protect everyone, protect
no one or only some?
REMARK (Dr. Ross): The TLV for asbestos fiber now being pushed is one-tenth
of a fiber per cubic centimeter. You cannot operate a mill or a
mine at that level.
REMARK (Dr. Langer): I will go one better. You cannot even regulate 0.1
fiber. You simply cannot count, without enormous time and expense
at this level.
REMARK (Dr. Ross): Right. But that is the regulatory direction right
now. Okay, now we just had the Department of Labor produce this
document with 152 more fibrous minerals. We have got about half
the earth's crust under the "asbestos" label. A regulation of a
tenth of a fiber per cubic centimeter and the mining industry is
dead as a doornail.
REMARK (Dr. Langer): I understand that problem and I agree with you that
this is oversimplified, it is simplistic; it is injurious to the
mining industry. I agree with that. It is based on the supposition,
the assertion, that any fibrous particle which reaches the alveolar
space migrates to the mesothelial surface and produces mesothelioma.
Some believe that. I believe that there are profound differences
in mineral species. But you have heard me say that before. What
other alternatives exist? What are the data?
QUESTION (Dr. Reeves): Why then the same TLV?
ANSWER (Dr.. Langer): In absence of data people extrapolate. There are
no alternatives.
REMARK (Mr. Gill): The only thing that concerns me about the conversation
between Drs. Reeves and Langer about fibrous talc and a TLV is that
there is not any TLV for fibrous talc. There is not anything in
AC6IH that says anything about fibrous talc. It says "asbesti-
form talc". That is a whale of a difference. I do not want to
leave any of you with the impression that that is listed as a
separate item, called "fibrous talc".
REMARK (Dr. Langer): I"want to thank all of the participants at the round-
table discussion and especially the audience for the stimulating
contributions.
619
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OCCUPATIONAL EXPOSURES IN THE MANUFACTURE AND
APPLICATION OF POLYURETHANE AND UREA FORMALDEHYDE
INSULATION SYSTEMS
by
Mr. Robert F. Herrick*
National Institute for Occupational Safety and Health
Cincinnati, Ohio
and
A.A. Alcarese, R.P. Reisdorf, and D.W. Rumsey
Enviro Control, Inc.
Rockville, Maryland
ABSTRACT
Polyurethane and urea formaldehyde foams are used for residential side wall in-
sulation and commercial insulation and roofing. Worker exposures to a variety
of airborne contaminants were studied in the manufacturing and application of
these two materials.
Industrial hygiene surveys at two polyurethane insulation manufacturing facili-
ties and two application'sites showed that airborne concentrations of methylene
diphenyl diisocyanate (MDI), several amine catalysts, fluorotrichloromethane
(Freon-11) and alpha-methyl styrene were very low during the manufacturing
processes. Exposures of workers applying the polyurethane foam insulation
were substantially higher, especially during insulation of the interior walls
in a refrigerated warehouse. Airborne MDI levels during interior application
exceeded the NIOSH recommended exposure limits.
Surveys at two manufacturing facilities of urea formaldehyde insulation showed
airborne formaldehyde concentrations which approached the NIOSH recommended
ceiling value (1 ppm) during resin production, and exceeded the recommended
celling value during resin drum filling. Worker exposures to formaldehyde dur-
ing foam installation from the exterior of residences (exterior retrofitting)
ranged around 1 ppm, while formaldehyde exposures during open-bay insulation
from the inside of residences exceeded 2 ppm. Observed levels of other airborne
contaminants during urea formaldehyde foam manufacturing and application were
very low.
*Presented by Mr. Robert JF\_IIerric1;.
621
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INTRODUCTION
The rising cost of energy has resulted in increasing demand for thermal
insulation materials, both in commercial and residential applications. Strong
growth trends are predicted through 1983 for foam insulation materials used in
residential side wall insulation and in commercial insulation and roofing. This
study was undertaken to characterize worker exposures in the manufacturing and
application processes of two foam insulation materials, polyurethane and urea
formaldehyde foam.
The findings I will present today summarize in-depth surveys performed at
two manufacturing facilities and two application sites for polyurethane foam;
and two manufacturing facilities and two application sites for urea formaldehyde
foam. This study was performed under NIOSH contract by Enviro Control, Incor-
porated of Rockville, Maryland, with the exception of one manufacturing facility
which was surveyed by NIOSH personnel. Applicators were chosen so that for each
foam insulation manufacturer selected, an applicator of the manufacturer's pro-
duct was included in the study.
POLYURETHANE FOAM INSULATION
Manufacturing
Polyurethanes are thermoplastic polymers produced by the condensation re-
action of polyisocyanate and hydroxyl-containing materials. In the case of
polyurethane foams used for thermal insulation, methylene diphenyl diisocyanate,
also known as diphenylmethane diisocyanate or MDI, or a mixture of about 50 per-
cent MDI and 50 percent polymerized MDI, known as polymethylene polyphenyl iso-
cyanate or PAPI reacts exothermally with one or more polyether polyols (com-
pounds containing more than one hydroxyl group) in an aqueous reaction cata-
lyzed by one or more organotin and amine catalysts. Carbon dioxide, which is
a by-product of the polymerization, and volatile fluorocarbon blowing agents
expand the polymer into a rigid foam.
/
The polyurethane foam insulation produced from this two component system
is a rigid material with high resistance to the flow of heat. When expressed
in terms of R values per inch of thickness, polyurethane foams typically have
R values of approximately 6, as compared with about 4 for urea formaldehyde
foam and 3 for mineral wool and fiberglass batts.
The polyurethane foam insulation systems included in this study are manu-
factured in facilities which specialize in compounding a wide variety of poly-
urethane systems. The base materials, consisting of MDI or PAPI, and polyether
polyols are manufactured elsewhere and shipped by railcar or truck to the com-
pounding facilities. The "A" side (or catalyst) of the polyurethane foam insul-
ation systems is produced by repackaging liquid MDI or PAPI into 55 gallon drums
from bulk storage, or by pumping MDI or PAPI to blend tanks where flame retar-
tdants (usually phosphate esters) are added and mixed at room temperature. The
product is then transferred to 55 gallon drums. In the facilities studied, "A"
side mixing and drumming is usually a one-man operation, performed two or three
times a week. The "B" side component or resin is a mixture of ingredients which
are also blended at room temperature. Some ingredients such as polyether polyols
may be piped directly to the blend tanks from bulk storage, while other raw mater-
ials such as fluorotrichloromethane, amine catalysts, and alpha-methyl styrene
622
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are added by pouring or pumping from smaller containers. After blending for
30 to 60 minutes, the finished resin is pumped into 55 gallon drums. Quality
control samples are collected during-the blending process and samples of the
finished resin are tested for foaming characteristics.
Personal and area samples were collected for MD1, several amine catalysts,
fluorotrichloromethane, alpha-methyl styrene, and methylene chloride. Samples
were analyzed by methods contained in the NIOSH Manual of Analytical Methods
when appropriate methods were available. Sampling and analytical methods for
the amines were developed by the contractor from NIOSH Method P&CAM 270 for
aminoethanol compounds.
Discussion
At Plant A, personal samples collected during two periods of catalyst drum
filling showed MDI concentrations ranging from less than the detectable limit
to 2 ppb (Table 1). Exposure levels measured at Plant B during catalyst drum
filling ranged from non-detectable to 5 ppb (Table 2).
Amine concentrations during resin blending and drumming at Plant A ranged
from non-detectable to 170 ppb for dimethyl ethanolamine and non-detectable to
810 ppb for dimethyl cyclohexylamine (Table 3). At Plant B, tetramethylbutane
diamine, triethylene diamine, and dimethyl ethanolamine were non-detectable,
while concentrations of dimethyl cyclohexylamine ranged from non-detectable to
63 ppb (Table 4).
Concentrations of fluorotrichloromethane (Freon-11), which is added as a
blowing agent, ranged from 0.95-96.0 ppm at Plant A and 4.4-193 ppm at Plant B
(Table 5).
During equipment cleanup at Plant A, methylene chloride was measured at a
level of 11 ppm over a 5-hour sampling period. Alpha-methyl styrene was not
detected in personal air samples at either plant.
Application
Typical polyurethane foam insulation applications include roof exteriors,
refrigerated warehouses, storage tanks, and other commercial applications. Dur-
ing this study, industrial hygiene surveys were performed during application of
polyurethane foam to the roof of a church for the purposes of sealing and in-
sulating and to the interior walls of a refrigerated room in a food warehouse.
Applicator A was surveyed at the church roofing site. The application pro-
cess consisted of removing loose gravel and tearing off areas of defective roof-
ing, then spraying polyurethane foam in four foot wide strips over the roof.
The foam spraying was performed with an airless spray gun, with the A and B com-
ponents heated to 60°C and pumped to the spray gun, where mixing takes place.
The foam expands to a thickness of approximately one inch and hardens within
one minute. A sillcone-based weather coating is applied after the foaming is
completed.
Applicator B was surveyed during insulation of a refrigerated room within
623
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LOCATION:
ACTIVITY:
TABLE 1. AIRBORNE MDI CONCENTRATIONS
PERSONAL SAMPLES
PLANT A
DRUM LOADER, FILLING CATALYST DRUMS
Date
10/24/79
10/25/79
Number of
Samples
2
3
Total Sampling
Time (Minutes)
32
61
Sampling Period
TWA (PPB)
<2.0
0.9
Range (PPB)
<2.0
<1. 0-2.0
NIOSH Recommended
Standard: 20 PPB
Ceiling
5 PPB TWA
TABLE 2. AIRBORNE MDI CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: PLANT B
ACTIVITY: CHEMICAL OPERATION LOADING CATALYST DRUMS
Date
10/31/79
10/31/79
11/01/79
11/01/79
Number of
Samples
6
3
4
2
Total Sampling
Time (Minutes)
206
99
263
177
Sampling Period
TWA (PPB)
2.0
0.6
0.7
0.3
Range (PPB)
<0. 8-5.0
<0.6-1.8
<0.2-2.3
<0.2-0.6
NIOSH Recommended
Standard: 20 PPB
Ceiling
5 PPB TWA
624
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TABLE 3. AIRBORNE AMINE CONCENTRATIONS PERSONAL SAMPLES
LOCATION: PLANT A
ACTIVITY: BLENDING AND DRUMMING RESIN
Compound
Dime thy lethanol Amine
Dimethylcyclohexyl Amine
Number of
Samples
10
10
Sampling Period
TWA (PPB)
62.6
240.2
Range of
Concentrations (PFB)
<64. 0-170.0
7.0-810.0
TABLE 4. AIRBORNE AMINE CONCENTRATIONS PERSONAL SAMPLES
LOCATION: PLANT B
ACTIVITY: BLENDING AND DRUMMING RESIN
Compound
Tetramethylbutane Diamine
Triethylene Diamine
Dimethylethanol Amine
Dimethylcyclohexyl Amine
Number ot
Samples
1
2
3
5
Sampling Period
TWA (PPB)
19.0
Range of
Concentrations (PPB)
Not Detected
(<56)
Not Detected
Not Detected
5-63.0
TABLE 5. AIRBORNE FLUOROTRICHLOROMETHANE CONCENTRATIONS
ACTIVITY: BLENDING AND DRUMMING RESIN
Location
PLANT A
PLANT B
Number of
Samples
7
5
Sampling Period
TWA (PPM)
34.6
45.3
Range ^
Concentration (PPM)
0.95-96.0
4.4-193.0
ACGIH - TLV: 1000 PPM
625
-------
a food storage warehouse. The application process consisted of spraying foam
onto the interior walls of the room to a thickness of approximately three inches.
Application was performed by a two man team, using airless spray equipment simi-
lar to that used at Site A.
Personal samples were collected on the foam applicators and the helpers
at Sites A and B during foam application and cleanup. Sample collection and
analysis were performed as previously described in the surveys of the poly-
urethane manufacturing facilities.
Discussion
Table 6 presents the results of two days sampling during application of
polyurethane foam to a church roof. The applicator's exposure to MDI ranged
from non-detectable to 9 ppb, while the helper's exposures ranged from non-
detectable to 1.9 ppb. Application of polyurethane foam to the interior walls
of a refrigerated warehouse generated MDI exposure levels of non-detectable to
68 ppb with 8 hour time-weighted averages (TWA) as high as 13 ppb for the appli-
cator, and exposures up to 28 ppb with a TWA of 6 ppb for the helper (Tables 7
& 8).
Airborne amine concentrations at Site A, the roof application, ranged from
non-detectable to 480 ppb for dimethyl cyclohexylamine and non-detectable to
70 ppb for triethylene diamine (Table 9). Amine concentrations at Site B ranged
from 17-170 ppb dimethyl cyclohexylamine and dimethyl ethanolamine was not de-
tected (Table 10).
Concentrations of fluorotrichloromethane ranged "from 1.6-13.0 ppm for the
outdoor application at Site A and from 33-180 ppm for the interior application
at Site B (Table 11).
Summary
At the two manufacturing facilities, airborne MDI concentrations during
blending and drum filling were low, ranging from below the limit of detection
to 5 ppb. Amine concentrations were below 1 ppm, fluorotrichloromethane levels
ranged from 0.95-193 ppm, and alpha-methyl styrene was not detectable at a level
of 84 ppb.
Airborne MDI levels measured during the outdoor application of foam to a
roof ranged from below the limit of detection to 9 ppb for the applicator and
the helper. The indoor application at Site B, however, generated MDI levels
up to 68 ppb, with daily TWAs as high as 13 ppb. The data indicates that the
indoor application of polyurethane foam presented higher exposures to MDI than
the outdoor applications, however, differences in the chemical formulations of
the systems may have had an effect on the observed MDI concentrations.
Concentrations of amine catalysts during foam application ranged from be-
low limits of detection to 480 ppb. Fluorotrichloromethane exposures ranged
from 1.6-180 ppm, and alpha-methyl styrene was measured at levels of 0.17 ppm
and 0.21 ppm during interior foam application.
626
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TABLE 6. AIRBORNE MDI CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: SITE A, CHURCH ROOF
ACTIVITY: EXTERIOR APPLICATION OR POLYURETHANE FOAM INSULATION
Date
11/19/79
11/19/79
11/20/79
11/20/79
Number of
Samples
6
(Applicator)
4
(Helper)
10
(Applicator)
7
(Helper)
Total Sampling
Time (Minutes)
255
270
219
214
Sampling Period
TWA (PPB)
2.7
0.8
2.1
1.3
Range (PPB)
<1. 0-9.0
<1.0-1.5
< 1.3-5. 3
<1.1-1.9
NIOSH Recommended
Standard: 20 PPB Ceiling
5 PPB TWA
10
-------
TABLE 7. AIRBORNE MDI CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: SITE B, REFRIGERATED WAREHOUSE
ACTIVITY: INTERIOR APPLICATION OF POLYURETHANE FOAM INSULATION
Date
12/19/79
12/20/79
12/21/79
Number of
Samples
7
(Applicator)
A
(Applicator)
5
(Applicator)
Total Sampling
Time (Minutes)
201
96
134
Sampling Period
TWA (PPB)
41
27
17
Daily
TWA (PPB)
13
5.0
5.7
Range (PPB)
20-68
< 12-55
<8.1-43
NIOSH Recommended
Standard: 20 PPB Ceiling
5 PPB TWA
CD
-------
TABLE 8. AIRBORNE MDI CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: SITE B, REFRIGERATED WAREHOUSE
ACTIVITY: INTERIOR APPLICATION OF POLYURETHANE FOAM INSULATION
Date
12/19/79
12/20/79
12/21/79
Number of
Samples
7
(Helper)
3
(Helper)
3
(Helper)
Total Sampling
Time (Minutes)
236
159
114
Sampling Period
TWA (PPB)
13
2.2
7.0
Daily
TWA (PPB)
6.0
0.6
2.0
Range (PPB)
A. 7-28
1.8-4.8
5.6-9.2
NIOSH Recommended
Standard: 20 PPB Ceiling
5 PPB TWA
t<0
-------
TABLE 9. AIRBORNE AMINE CONCENTRATIONS PERSONAL SAMPLES
LOCATION: SITE A, CHURCH ROOF
ACTIVITY: EXTERIOR APPLICATION OF POLYURETHANE FOAM INSULATION
Compound
Dlmethylcyclohexylamine
Triethylene Diamine
Number of
Samples
6
6
Sampling Period
TWA (PPB)
189
48
Range of
Concentrations (PPB)
< 8-480
< 30-70
TABLE 10. AIRBORNE AMINE CONCENTRATIONS PERSONAL SAMPLES
LOCATION: SITE B, REFRIGERATED WAREHOUSE
ACTIVITY: INTERIOR APPLICATION OF POLYURETHANE FOAM INSULATION
Compound
Dime t hyle thano lamine
Dimethylcyclohexylamine
Number of
Samples
4
4
Sampling Period
TWA (PPB)
55
Range of
Concentration (PPB)
Not Detected
17-170
TABLE 11. AIRBORNE FLUOROTRICHLOROMETHANE CONCENTRATIONS
PERSONAL SAMPLES
ACTIVITY: POLYURETHANE FOAM''INSULATION SPRAYING
Location
SITE A
SITE B
Number of
Samples
4
4
Average
Concentration (PPM)
5.7
99.0
Range of
Concentration (PPM)
1.6-13.0
33-180
ACGIH TLV: 1000 PPM
630
-------
UREA FORMALDEHYDE FOAM INSULATION
Manufacturing
Urea formaldehyde foam insulation systems consist of two components: a
resin and a catalyst or foaming agent. The resin component is produced by
condensation reactions of urea and formaldehyde under alkaline conditions form-
ing methylol derivatives which undergo further polymerization to form the resin.
The particular characteristics of each resin are determined in part by the pre-
sence of additives such as alcohols and phenol. The catalyst of foaming agent
is an aqueous mixture of acids and sulfonic acid emulsiflers.
The manufacturing facilities included in this study specialize in the pro-
duction of urea formaldehyde insulation systems. Both facilities produce resin
in a batch process, manufacturing 2-10 batches per week. The production sche-
dule varies with seasonal demand for insulation materials. At Plant C, the
resin component is manufactured in batches, utilizing 37 percent formaldehyde
solution, prilled urea, furfuryl alcohol, ammonium hydroxide, a sugar solution,
and a proprietary flame retardant as ingredients. The resin is formed by par-
tial polymerization of these base materials in an alkaline reaction mixture.
The finished resin is cooled and packaged in 55 gallon drums.
At Plant D, the resin component is manufactured by a patented process
utilizing methylolurea as the base material, along with phenol and small amounts
of acetaldehyde. The resin is produced by polymerization of methylolurea, phenol,
and urea in an acid catalyzed reaction. The reaction proceeds until the desired
degree of condensation is acheived, then the reaction is stopped, a fructose
solution and additional"ureaare added, and the mixture is cooled and packaged
in 55 gallon drums.
The foaming agent or catalyst is a mixture of sulfonic acid emulsifying
agents and dilute acids. At Plant C, the foaming agent is produced as a con-
centrate which is diluted with water by the foam applicator. Plant D produces
a foaming agent which is delivered to the applicator at working strength.
Personal and area samples were collected for formaldehyde, ammonia, and
furfuryl alcohol during the resin manufacturing processes at Plant C. At Plant
D, samples were collected for formaldehyde, acetaldehyde and phenol. Samples
were analyzed by methods contained in the NIOSH Manual of Analytical Methods.
Formaldehyde measurements at Plant D were also made by collection on solid sor-
bent tubes and analysis by ion chromatography as described in a method developed
by the NIOSH Division of Physical Sciences and Engineering.
Discussion
Formaldehyde levels measured in samples collected during resin production
at Plant C ranged from 0.12 to 0.55 ppm (Table 12). Higher levels were observed
during resin drumming, with personal samples collected on the cook's assistant
ranging from 1.8-5.4 ppm (Tables 13 & 14).
Plant C packages its resin in returnable drums, and these drums are washed
with a hot water spray before they are reused. Small amounts of resin may be
631
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TABLE 12. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: PLANT C
ACTIVITY: FORMULATING RESIN - COOK
Date
9/25/79
9/26/79
Number of~~'~~~~
Samples
4
5
Total Sampling
Time (Minutes)
518
506
Sampling Period
TWA (PPM)
0.27
0.36
Range (PPM)
0.20-0.35
0.12-0.55
NIOSH Recommended
Standard: 1 PPM (Ceiling)
U>
10
-------
TABLE 13. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: PLANT C
ACTIVITY: FORMULATING AND DRUMMING RESIN (COOK'S ASSISTANT)
Date
9/25/79
9/26/79
Number of
Samples
3
6
Total Sampling
Time (Minutes)
506
460
Sampling Period
TWA
-------
TABLE 14. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL SAMPLES
COOK'S ASSISTANT - DRUM FILLING
Date
9/25/79
9/26/79
Sampling
Period
62
30
25
30
Activity
Drum Filling - Lid Off
Drum Filling - Lid Off
Drum Filling - Lid On
Drum Filling - Lid Off
Concentration
1.8
5.4
2.1
2.6
NIOSH Recommended Standard: 1 PPM (Ceiling)
634
-------
in the drum as it returns to the plant. Formaldehyde levels measured during
drum washing ranged from 0.2-0.74 ppm (Table 15).
Although the foaming agent does not contain formaldehyde, levels of 0.06-
0.34 ppm formaldehyde were observed in personal samples of the foaming agent
blender (Table 15). This employee spent brief periods of time near the reactor.
Ammonia concentrations ranged from non-detectable to 15 ppm for the cook
and cook's assistant during resin production (Table 16). Furfuryl alcohol was
non-detectable at a level of 0.3 ppm.
At Plant D, formaldehyde levels ranged from 0.34 - 0.45 ppm during resin
production. Personal samples collected during resin drumming ranged from 0.18 -
1.28 ppm. Phenol was non-detectable at a level 0.3 ppm, and acetaldehyde was non-
detectable at a level of 1.3 ppm.
Application
In the application of urea formaldehyde foam, the catalyst-foaming agent
mixture is pumped into an application gun where it is expanded into bubbles
with compressed air or nitrogen. The foamed catalyst is mixed with resin at
the nozzle of the application gun. The resin and catalyst react on the surface
of the bubbles and the resin cures to self-supporting foam within one minute.
Complete curing of the foam may require 48-72 hours up to several weeks after
application, depending on factors such as outside temperature and formulation
of the foam. The urea formaldehyde foam produced from this system is a solid
material with a density of approximately 2.5 Ib/cubic foot.
Urea formaldehyde foam insulation is installed in the sidewalls of exist-
ing structures; this application is known as retrofit. It is also used in side-
wall insulation in new construction by a procedure known as open-bay application.
Both application techniques were surveyed in this study.
Applicator C was surveyed during retrofit of three residences. The appli-
cation team consisted of five men* one of whom was a manufacturer-certified
applicator. The retrofit application began with all five men opening the struc-
ture. Opening is the industry term for gaining access to the wall cavities,
and in approximately 90 percent of the jobs it is done from outside the house.
Holes are drilled in masonry and wood. Aluminum siding and shingles are usually
removed, and the weatherboard is knocked through with a hammer. Before foaming
begins, the applicator performs several quality control procedures, including
measurements of foam density, and test cones known as beehives are shot to eval-
uate foam properties. Improper proportions of the components can cause a con-
dition known as vanishing foam, in which foam appears to be normal when it
leaves the gun but collapses within about 10 minutes. Applicators sometimes
taste the foam as part of their quality control procedures. When the resin,
catalyst, and compressed air or nitrogen are metered in the correct proportions,
the foam has the consistency of shaving cream. Unlike polyurethane foam, urea
formaldehyde foam is fully expanded when it leaves the gun. In retrofit appli-
cations, it flows into cavities and sets within about one minute.
635
-------
TABLE 15. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: PLANT C
ACTIVITY: DRUM WASHING AND FOAMING AGENT BLENDING
Date
DRUM WASHING
9/25/79
9/26/79
FOAMING AGENT
BLENDING
9/25/79
9/26/79
Number of
Samples
2
3
2
3
Total Sampling
Time (Minutes)
407
411
411
396
Sampling Period
TWA (PPM)
0.52
0.30
0.24
0.18
Range (PPM)
0.23-0.74
0.20-0.47
0.15-0.34
0.06-0.26
NIOSH Recommended
Standard: 1 PPM (Ceiling)
CO
o\
-------
TABLE 16. AIRBORNE AMMONIA CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: PLANT C
ACTIVITY: FORMULATING RESIN
Date
9/27/79
(Cook)
9/27/79
(Cook's
Assistant)
Number of
Samples
4
4
Total Sampling
Time (Minutes)
477
507
Sampling Period
TWA (PPM)
1.9
0.28
Range (PPM)
0.96 - 15
<0.13 - 1.6
NIOSH Recommended
Standard: 50 PPM (Ceiling)
-------
The applicator begins foaming and as he moves along a wall, other members
of the crew follow behind and remove excess foam and close the house, returning
it to its original condition.
Applicator C also performed open-bay application to buildings under con-
struction. In open-bay applications, the air pressure is increased and a thin
coat of foam is sprayed onto the wall surface. After this scratch coat has been
applied, the air pressure is reduced and the cavity between the studs is filled
with foam. In some cases, a plastic trowel is attached to the end of the appli-
cation hose to smooth the foam. Approximately 15 minutes after foaming, a flat
shovel is used to scrape away the excess foam so the insulation is flush with
the studs. A polyethylene sheet is nailed to the studs to form a vapor barrier.
Applicator D was surveyed during retrofit of two residences. The applica-
tion process was virtually identical to that described for Applicator C, except
that Applicator D used a two man team to install the foam.
Personal and area samples were collected during setup, foam application,
closing, cleanup, and maintenance activities associated with foam installation.
Sampling and analysis were performed as previously described in the surveys of
the insulation manufacturing facilities.
Discussion
For Applicator C, personal exposures to formaldehyde during exterior retro-
fit ranged from non-detectable to 1.2 ppm_(Table 17)_. Jhe formaldehyde exposures
of laborers ranged from non-detectable to 0.65 ppm,~with the highest exposures
observed during cleanup of waste foam around the site (Table 18).
Area samples collected in the van during site preparation, foaming clean-
up, and driving back to the warehouse ranged from 0.07-2.0 ppm. Concentrations
of formaldehyde in the warehouse before and after the work day ranged from 0.17-
0.85 ppm. Samples collected for ammonia and furfuryl alcohol were below detect-
able limits of 0.1 and 0.3 ppm, respectively.
Applicator C was also sampled during open-bay foam installation. Formalde-
hyde levels during foaming ranged from 1.1-2.4 ppm, and from 0.86-2.3 ppm during
foam scraping (Table 19).
Applicator D was sampled during exterior retrofit foam installation. Formal-
dehyde exposures to the applicator ranged from 0.06-1.3 ppm, while the applica-
tor's assistant was exposed to formaldehyde at levels ranging from non-detect-
able to 0.5 ppm (Tables 20 and 21). The highest exposures were measured while
the assistant was working closely with the applicator (Table 21). Area samples
collected in the van during site preparation, foaming, cleanup, and driving
back to the warehouse ranged from 0.02 to 0.33 ppm.
Summary
In the survey of the urea formaldehyde insulation manufacturing facilities,
the highest formaldehyde levels were observed during resin drum filling with
levels as high as 5.4 ppm measured. Formaldehyde levels during resin production
ranged from 0.12 to 0.74 ppm. The only other contaminant which was detectable
638
-------
TABLE 17. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: APPLICATOR C
ACTIVITY: APPLICATOR EXPOSURES DURING EXTERIOR RETROFIT
Date
12/06/79
12/10/79
12/11/79
Number of
Samples
4
5
3
Total Sampling
Time (Minutes)
261
249
145
Sampling Period
TWA (PPM)
0.37
0.22
0.27
Range (PPM)
<0.03 - 1.2
0.03 - 0.83
0.14 - 0.35
TABLE 18. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL SAMPLES
LOCATION: APPLICATOR C
ACTIVITY: LABORER EXPOSURES DURING EXTERIOR RETROFIT
Date
12/06/79
12/10/79
12/11/79
Number of
Samples
2
5
3
Total Sampling
Time (Minutes)
172
312
90
Sampling Period
TWA (PPM)
0.08
0.18
0.20
Range (PPM)
0.06 - 0.11
<0.04 - 0.65
0.15 - 0.32
639
-------
TABLE 19. FORMALDEHYDE EXPOSURES DURING
OPEN-BAY APPLICATION - 12/12/79
Sampling
Period (Min)
34
31
30
27
34
35
31
12
Concentration
(PPM)
1.1
2.4
1.1
1.6
0.86
2.3
1.6
2.3
Activity
Foam Application
Foam Application
Foam Application
Foam Application
Foam Scraping
Foam Scraping
Foam Scraping
Foam Scraping
640
-------
TABLE 20. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL EXPOSURES
LOCATION: APPLICATOR D
ACTIVITY: APPLICATOR EXPOSURES DURING EXTERIOR RETROFIT
Date
11/27/79
11/28/79
11/29/79
11/30/79
Number of
Samples
5
5
1
6
Total Sampling
Time (Minutes)
234
291
32
299
Sampling Period
TWA (PPM)
0.12
0.34
0.45
0.71
Range (PPM)
0.07 - 0.52
0.10 - 0.80
0.06 - 1.3
-------
TABLE 21. AIRBORNE FORMALDEHYDE CONCENTRATIONS
PERSONAL EXPOSURES
LOCATION: APPLICATOR D
ACTIVITY: ASSISTANT'S EXPOSURE DURING EXTERIOR RETROFIT
Date
11/27/79
11/28/79
11/29/79
11/30/79
Number of
Samples
2
3
2
5
Total Sampling
Time (Minutes)
99
162
186
351
Sampling Period
TWA (PPM)
0.19
0.14
0.07
0.06
Range (PPM)
0.06 - 0.37
<0.09 - 0.26
<0.03 - 0.13
<0.04 - 0.50
-------
during resin production was ammonia, which was measured in concentrations up
to 15 ppm.
Formaldehyde exposures to applicators performing exterior retrofit ranged
from non-detectable to 1.3 ppm. Open-bay application was found to produce sig-
nificantly higher formaldehyde levels, ranging from 0.86-2.4 ppm. Other air
contaminants were not detected during retrofit or open-bay applications.
Conclusions
In-depth industrial hygiene surveys of two polyurethane foam insulation
manufacturers showed that worker exposures to MDI, a variety of amines, flouro-
trichloromethane, and alpha-methyl styrene were very low. Surveys of polyure-
thane insulation application sites showed airborne MDI levels above the NIOSH
recommended standard during interior foam application, while exposures during
outdoor foam applications were substantially lower. While the lack of natural
ventilation during interior application was certainly a contributing factor to
the higher observed MDI concentrations, differences in the chemical formulations
of the foam systems may have also had an effect.
Surveys at urea formaldehyde foam manufacturers showed that airborne for-
maldehyde levels during resin production approached the NIOSH recommended ceil-
ing value and exceeded it during resin drum filling. Concentrations of other
air contaminants were generally very low.
Application of urea formaldehyde foam by exterior retrofit resulted in
worker exposures at about the recommended ceiling value, while interior (or
open-bay) application generated formaldehyde levels substantially in excess of
the recommended ceiling values. Comparisons of exposures during exterior re-
trofit and open-bay application of the same foam system indicate that lack of
ventilation during indoor application is the cause of elevated airborne formal-
dehyde concentrations.
Of the eight manufacturing and application facilities studied, only the
manufacturers of polyurethane systems had implemented engineering controls to
reduce exposure levels. The applicators of polyurethane insulation sometimes
wore paint spray respirators, however, due to the sensitizing properties of
MDI, these respirators do not provide an adequate degree of protection. The
manufacturers and installers of urea formaldehyde foam were not employing en-
gineering controls or respiratory protection. Preliminary results of inhalation
studies indicate that formaldehyde has caused nasal cavity cancer in rats. NIOSH
has recommended that exhaust ventilation be incorporated in urea formaldehyde
manufacturing processes, especially drum filling. Workers applying urea formal-
dehyde insulation should wear chemical cartridge respirators with full-face masks.
643
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QUESTION
ANSWER
REMARK
REMARK
DISCUSSION ON FOAMS
(Mr. Wright): I am with the Steelworkers.
I have a couple of quick technical questions. One is about the
sampling for MDI; was MDI sampled for as a vapor or as a particu-
late or as both?
(Mr. Herrick): We used the base method, which is recognized to under-
sample particulate MDI; therefore, I believe our values may be on
the low side in the application processes. In the manufacturing
processes, I think the values are fairly accurate because there was
no aerosolization of the MDI. I think there is a strong possibility
that we undersampled in the application sites.
(Mr. Wright): There is at least one recent study in a manufacturing
location that indicated a sizeable fraction of MDI in the air
existed as a particulate.
(Mr. Herrick): I think you are referring to the studies performed
at Tulane where MDI was vaporized. In that case, a sizeable frac-
tion of MDI would certainly exist as particulate, but we were
dealing with MDI at room temperature. The MDI was not heated to
generate a known concentration, which is what was done in the other
studies.
Your point is certainly well taken, however; NIOSH is actively
engaged in developing better methods for sampling isocyanides in
their particular forms.
v
QUESTION (Mr. Wright): A question about that same reference. Was there any
"Moca"* used as a catalyst in the system, or in other foaming
systems, or for making an insulation material?
ANSWER (Mr. Herrick): We investigated that in the course of the surveys
and found to the best of our knowledge that "Moca" is not being
used throughout the industry in insulation systems at this time.
QUESTION (Chairman Rowe): How long has this material been used in the United
States and what percentage of the market does it take up in com-
parison to the conventional types of insulation?
QUESTION (Mr. Herrick): Which system are you referring to?
ANSWER (Chairman Rowe) : Both the polyurethane and the urea-formaldehyde
foam versus, say, fiberglass.
Trademark for 4,4-methylenebis(2-chloro-aniline)
644
-------
ANSWER (Mr. Herrick): The market share for ureaformaldehyde was doing
quite well over the last 2 or 3 years, but as you all know, there
has been adverse publicity given to those products on the market,
which could cause problems. So the market share for ureaformal-
dehyde has pretty much dropped right off the bottom. When we did
these surveys, we found there were really only two companies en-
gaged in what could even be considered close to full-time pro-
duction of ureaformaldehyde foam systems.
In the case of polyurethane, it is quite a different picture.
The future is very bright for polyurethane systems. There are
a couple of companies expanding their capability to produce MDI
and one of the major reasons is the anticipated use in insulation
systems.
I am sorry I do not have any hard numbers for market share, but
I could get them for you. This information will be published as
a NIOSH technical report and will have more of the background
information you refer to.
645
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HUMAN PULMONARY FUNCTION STUDY (5 YEARS) ON OCCUPATIONAL
ISOCYANATE EXPOSURE
by
Hans Weill, M.D.
Department of Medicine
Tulane University School of Medicine
New Orleans, Louisiana
ABSTRACT
A previously unexposed industrial cohort in TDI (toluene diisocyanate) manu-
facturing was investigated over a 5-year period with collection of environ-
mental and biologic response data. In addition to scientific questions
addressing the incidence, determinants and mechanism of susceptibility to
low levels of TDI vapor (between 4 and 5 percent of the population became
TDI "reactors"), attention was directed toward the possibility that a general
adverse effect on airways function might occur in this population of 223 men.
Extensive personal monitoring characterizing the exposures of 42 jobs through
2000 continuous 8-hour personal samples allowed the individual reconstruction
of cumulative exposure in each study participant. Measurement of lung
function included lung volumes, maximum expiratory flow rates and diffusing
capacity. Lung function testing was performed at the plant site on nine
different occasions over the 5-year period, using the mobile pulmonary
function laboratory.
Smoking adversely influenced the longitudinal decline of ventilatory function
(FVC and FEVi). After accounting for smoking and atopic status, significant
differences between exposure categories were found for annual declines in FEVi
FEV percent, and FEFzs-ys. The exposure-related effect on annual declines in
these measurements of expiratory flow was slight in the total population, but
when the study group was divided by smoking history it was found that the
exposure-related effect was confined to the nonsmokers and masked or not
present in the smokers. Additionally, some TDI reactors have failed to
attain preexposure or presensitization values of FEVi or FEF2s_75 despite
transfers to other areas in the chemical complex.
I am going to present a brief summary of a study that was recently re-
ported to NIOSH in final form. This report will be available to the public.
In 1973 with the support of the National Institute of Occupational
Safety and Health, and with the cooperation of a major chemical company, the
members of my unit were invited to engage in a five year prospective
647
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longitudinal study of a working population exposed to TDI, toluene diisocyanate,
This population works in a process which occurs before the foaming process that
was discussed in the previous presentation. TDI manufacturing had not previ-
ously been a part of the manufacturing operations of this chemical plant in
southwest Louisiana. We had a unique opportunity to study a population before
their exposure.
The purpose of this very complex study, a multi-disciplinary study, was
to determine the influencing factors in any acute or chronic respiratory
effects that may emerge from this exposure.
There were initially 168 members of this working population in the TDI
plant. In the first two years of this study, new members of the work force
engaged in this aspect of the manufacturing were added to the cohort.
Ultimately, 277 people were available for study. These individuals were
studied at various times over a 5-year period, not at each of the observation
points, but with a minimum number being required for inclusion in the data
analysis.
The TDI plant that we studied cost about $60 million to build in the
early to mid-1970's. At that time gaskets were not too expensive, but TDI
spills caused by bad gasketing occurred. When a large leak occurs there is,
of course, a very high vapor concentration of this volatile material.
One of the known effects of exposure to isocyanates, either in manu-
facturing or in foaming operations, is an acute respiratory disease,
properly called "asthma." TDI produces intolerance, at times, to low levels
of exposure. In our population between 4 and 5 percent of the population
became intolerant. Age and smoking status varied among the individual
workers, but smoking did not seem to be an important influencing factor in pro-
ducing intolerance. Some workers had positive TDI bronchial provocation chal-
lenges in the lab, whereas some did not, at the levels of exposure that we
used. Some were atopic, that is they had an allergic diathesis, as was indi-
cated by two or more positive skin tests to common inhalant allergens whereas
others were not. Those eliciting a positive response were about what you would
expect in the general population; therefore, atropy was not an important influ-
encing or predicting factor.
Some individuals had known exposures to high concentrations of TDI; some
individuals developed symptoms as early as less than a week after the first
exposure, whereas others took as long as a couple of years to first develop
these symptoms. Host of these individuals did have complaints in the first
year.
We were able to reproduce the bronchial spasm in the laboratory with
varying patterns, as have other researchers, fy carefully monitoring the
levels of exposure and following the medical course using workers' respiratory
status and various patterns of bronchial provocation, a pattern emerged. An
acute response, where a drop in ventilatory capacity occurs immediately
after a 15-minute exposure, or a late response, where a drop may occur some
hours later and is usually less readily reversed, or a dual response of both
an acute and a late response may develop.
648
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TDI is a simple chemical and if it acts as an allergen, it presumably
acts as a haptene that must be conjugated with a protein. By using what was
touted to be,, perhaps, an advanced rash test (developed at the University of
Pittsburgh) that measured specific Ig antibodies, we found that only 15 or
18 percent of our acute reactors did in fact, have positive tests. We could
not demonstrate that IgE allergy, the classical asthma type allergy, was
the important factor in the mechanism of most of these instances.
Something did seem to happen in these people at -the cellular level.
The ordinary release of cyclic AMP by mast cells, which is good for the
bronchi, dilates the bronchi. When stimulated with known activators of
cyclic AMP, the response is limited. There seems to be an alteration of the
dose response curve for the cyclic nucleotide. For some reason, people who
have become reactive have a depressed release or ability to release cyclic AMP.
We do not know exactly why 4 to 5 percent of an exposed population become
intolerant.
What about the outcome of these acute problems? A followup of these
acute reactors, shows two measurements of expiratory flow, even after sensi-
tlzation was recognized. After the workers were ostensibly removed from
exposure, approximately 40 percent of these reactives continued to have un-
anticipated declines in their ventilatory function. This suggested to us
that some long-term effects may occur even after exposure ceases.
This has also recently been found with western red cedar dust exposure
and other causes of occupational asthma. Investigators in Vancouver found
that removing these individuals from exposure did not always lead to complete
reversal of their disease.
We were interested in characterizing exposure to TDI, to learn its more
general effect on respiratory health and the development of dose response rela-
tionships. Initially, we measured exposure with a continuous monitor using a
chemically impregnated paper tape. In the first 2 years, there were frequent
excursions above 0.02 parts per million in both production areas and in drumming.
In the last three years, we were able to develop personal sampling
information. We would produce 8-hour continuous profiles of the workers'
isocyanate vapor exposure. There was considerable variability and
fluctuation in the exposure over an 8-hour shift. We performed 1,949
characterizations of the personal exposures of persons representing 42 job
titles, to reconstruct for each individual a personal cumulative exposure
to use to correlate with the biological events that we saw. If you take
1,949, 8-hour time-weighted samples, and perform a frequency distribution in
various concentrations (parts per billion), you see a marked skewing. The
distribution becomes more symmetrical if you convert this to a large scale.
We were then able to develop high, moderate, and low exposure categories.
Ultimately, we were able to generate exposure categories for each of these
42 jobs. Then, by finding out who worked where and when, each individual
was, by summation, assigned an exposure profile. In a healthy population
the percent predicted for measurement of expiratory flow, lung volumes, and
diffusing capacity is nearly 100 percent. The average annual change of forced
649
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expiratory volume in one second, a very stable measurement, will be used to
illustrate changes in the population studies. As an Indicator of long-term
air-ways effect we used the annual change in lung function, by exposure groups.
Using this method we found the smoking effect which would be expected and an
exposure effect. We found a significant effect on average annual change in lung
function by TDI exposure in people who never smoke; a difference in average
annual change of somewhat less than 40 milliliters per year. The high expo-
sure group had about the same decline per year as the smokers. In the ex-
smokers and the current smokers the trend was in the same direction, but there
was some masking of this exposure-related effect, which was significant in
the people who never smoked.
This is not the first time an occupational exposure effect has been
demonstrated only in non-smokers. It is commonly held that smoking enhances
an exposure effect. But it does not necessarily have to do that, especially
when we are dealing with air-ways disease and not malignancy. The effect
here, fairly stated, is a small effect. The average annual decline in FEVi
and other expiratory flows, showed about the same results based on cross-
sectional predicted data. It is only about 27 or 30 milliliters per year,
and the high exposure group did not exceed that level very much. In longi-
tudinal studies, however, that decline may be smaller but even so, it is a
small effect. It is a modest effect and we think it is related to exposure,
after such things as smoking and atrophy are accounted for in the regression
equations.
In conclusion we have demonstrated that there are substantial exposures
in this manufacturing operation. Both continuous area and personal monitors
have demonstrated that essentially everybody in this study had at one time
or another been exposed. Over the 5-year period, there was no systematic
exposure trend demonstrated. We found that these various expiratory flow
rates, which are measurements or indicators of air flow function or
obstruction, are significantly related after controlling for smoking and
atopic status to TDI dose. The same significance was established whether or
not we measured dose by cumulative method or time spent above a certain
level. As I have already mentioned, these expiratory flows were not signi-
ficantly different from the annual declines from cross-sectional studies.
But these particular expiratory flows were significantly greater than those
prediction values would lead you to expect. There was a smoking effect,
which helped to validate these longitudinal data. And, as I have already
mentioned, the effect of TDI exposure of FEVx annual change_pr other expi-
ratory flows appears mainly in the nonsmokers and was perhaps masked in
smokers.
Prevalence of bronchitis and shortness of breath increased from the pre-
exposure baseline in the high exposure category, as measured by cumulative
exposure, but these increases were not significant. As I have mentioned,
about 4 percent of the population became acutely reactive or sensitized or
susceptible or intolerant, which is in keeping with the limited data that
are^available on this in the world literature. You have to remember that in
this situation, for the first time it was possible to get true incidence
data, that is the appearance of sensitization. In the other limited studies
that are available that was not possible because preexposure information was
650
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not available. Smoking and atrophy did not seem to be important predictors
of whether or not somebody would become intolerant. As I have already
suggested, some of these people have, so far, failed to obtain preexposure
or presensitization expiratory flows. This is in keeping with the very
latest reports a month or two ago at the American Thoracic meeting, from the
Vancouver group on the western red cedar dust situation.
Although we did not feel justified in going above 0.02 parts per million
in the bronchial provocation studies in the laboratory* we know that where
this has been done, some people who are clinically intolerant to TDI vapor
will respond not to 0.02 parts per million but to higher levels of exposure.
Therefore, a negative challenge test at 0.02 parts per million does not
necessarily mean the individual has not become reactive or intolerant. It
•Just means that he is not reacting to that level. Again, there are ethical
and perhaps even legal questions involved in exceeding the standard or TLV
in the laboratory in exposure situations.
These last conclusions deal primarily with the immunology, which I have
already indicated, the bottom line suggests that we still do not know. We
think something is going on at the receptor level. Why some people have this
abnormality and develop an inadequate response to stimuli to secrete cyclic
AMP is not clear.
651
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DISCUSSION ON ISOCYANATE
QUESTION (Mr. Anderson) : I am wondering if it is possible that there might
be isocyanates in cigarette smoke that allow one to build up an
immunity to i-socyanates, like one can build up an immunity to
arsenic by being exposed to low levels of arsenic?
ANSWER: (Dr. Weill): That is an interesting question. We came up with
several possible explanations and that was not one of them.
Cigarette smoke is very complex; as all of you know, it contains
many chemicals and particulates, Isocyanates do occur widely.
For instance, of some interest to us was one of our individuals who
became TDI reactive all of a sudden and could not tolerate one
of his favorite foods, radishes. He developed severe bronchial
spasm when he ate radishes. He ultimately lost his TDI
sensitivity and then could eat radishes again. Radishes do con-
tain an isocyanate. I do not know about cigarette smoke, but it
is an interesting possibility.
QUESTION (Mr. Sales): All along we have been talking about rather stable
minerals with long lifetimes, but isocyanates are noted for their
reactivity. I wonder if the fact that these materials are active
has been taken into account.
ANSWER (Dr. Weill): You are quite right. When TDI hits the moist
bronchi mucosa, it does change; it is no longer in its chemical
form and it is highly reactive. Something about either it or its
transformation or its product produces the kinds of problems that
I summarized.
We do have an interest in this. It is a very hard thing to get at.
It would easily be studied in the animal model; unfortunately,
so far there is no animal model for TDI asthma.
652
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CRITERIA FOR ANIMAL, TISSUE CULTURE, AND BIOCHEMICAL STUDIES ON
ASBESTOS, MINERAL DUSTS, AND PROPOSED SUBSTITUTES FOR ASBESTOS
by
Earl S. Flowers, Ph.D.
Flow General Incorporated
McLean, Virginia
ABSTRACT
There are numerous studies available on the animal toxicity and adverse
tissue effects of asbestos and mineral dusts to allow development of short-
term in vivo and in vitro tests of proposed substitutes for asbestos. The
in vitro tests available comprise measures of viability, cytotoxicity,
hemolytic activity, release of enzymes from damaged cells, and similar
measures of cellular or biochemical functions. In vivo testing involves a
wider variety of studies ranging from short-term immunologic, histologic,
and physiologic response in animals to lifetime studies such as determination
of tumor yields or chronic fibrosis. Appropriate testing of proposed sub-
stitutes requires use of tests to compare mechanisms of action for proposed
substitutes with those for asbestos and other mineral dusts.
I have been attending the sessions over the past few days. I was
particularly interested at .the first session in the remarks by Dr. Warren
Muir in regard to the duty of the EPA, under TSCA and various legislative
acts, to eliminate the unreasonable risk of exposure to asbestos in the United
States environment.
During the workshop we have had descriptions of some rather detailed
inhalation toxicology studies going on with respect to vitreous glass. These
studies have been in progress for about two and one-half or three years.
With the protocols felt necessary for the in vivo tests described, there is
something like a million dollars a year being spent over a five year period.
In the past few days some 60 substitutes have been presented here.
If all of these were tested according to the protocols for vitreous glass,
that would be roughly $300 million to perhaps half a billion dollars to
test substitutes for asbestos. That amounts to $60 million a year for a
five year period to test substitutes for a material that represents a raw
material cpst of about $220 million a year in the U.S. economy.
653
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Obviously, one would not be able to do complete in vitro and in vivo tests
for all proposed substitutes to that extent_re£ardejLby some_as necessary_to
produce data for risk assessment and unreasonable risk decisions under TSCA
procedures. One approach that comes out of this economic dilemma is to use in
vitro tests to establish priorities for in vivo tests.
My particular talk actually addresses two different levels of criteria for
the animal, tissue culture, and biochemical studies on asbestos, mineral dust,
and proposed substitutes.
Sometimes these two different levels of criteria may be in conflict with
each other. One level is that of the regulatory or administrative criteria
for generation of data to determine exposure and adverse effects so that one
can make unreasonable risk decisions and develop regulations. The other
is the scientific level of criteria to do a fairly complete characterization
of toxic effects and identification of underlying mechanisms for the action
of asbestos or proposed substitutes. In developing a proposed substitute for
asbestos and reaching the stage of commercial development, we came up against
some very difficult questions, essentially in the realm of: Where do we
go from here to develop data that will be persuasive to EPA? If successful
in our tests, what data would allow the use of our material as a substitute
for asbestos?
Figure 1 starts with the basic unreasonable risk decision process and
the mandate under the toxic substances control act for EPA to manage the
degree of risk on exposure to chemical, physical agents, and other substances
to an acceptable level in our environment. In going through the unreasonable
risk decision process I will show how this relates to developing acceptable
test protocols and criteria for substitutes.
The unreasonable risk decision process or evaluation starts with the
submission of notices and test data. In the pre-manufacturing notification
process there is a requirement for a determination of whether the information
submitted is sufficient to perform evaluations of risk.
If the data is sufficient, then the first requirement is to see if there
is a substantial risk as indicated by the data using appropriate risk assess-
ment methodologies. I understand that such methodologies are presently under
development.
If the data in the pre-manufacturing notice is insufficient to allow an
assessment of risk, then the EPA, under Section 4 of TSCA, can require the
submission of additional data. This leads to another reiteration of the pre-
manufacturing notification and highlights the issues of acceptable test
criteria.
During this time, it is the duty of the administrator to provide interim
protection, and he has various options for unreasonable risk protection
during the decision process. He can limit or prohibit manufacture or use,
seek an injunction through the court process, or decide to invoke one or all
654
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Figure 1. Unreasonable risk decisions and required procedures under TSCA.
655
-------
of the seven regulatory options contained under Section 6 of TSCA. These
options range from labeling to an outright ban of material. The administrator
may simply require that the manufacturer maintain records and conduct medical
surveillance of employees during the marketing, testing, and interim manu-
facturing of such material while the process of determining the degree of risk
or the existence of an unreasonable risk continued.
Under Section 4 of TSCA, there are various sections allowing the admin-
istrator to require additional tests. The public can petition the EPA for
a variance during test marketing, under 4(b). Under Section 4(g), Congress
recognized that thes6 tests would be potentially expensive and that the public,
or interested individuals, could petition the EPA for acceptable test protocols
to develop the information in a cost-effective manner. Data from such tests
could be used to submit a pre-manufacturing notification. A plausible
assumption test protocols, if successful, would allow the EPA to perform a risk
assessment and make a determination on whether or not to allow manufacture, use,
or distribution of the proposed product in the United States.
The decision process for testing and successful introduction of the
proposed substitute for asbestos is shown in Figure 2. To eventually come up
with an acceptable substitute, one must use in vitro and in vivo tests that
are available. These tests may be obtained from reviews of the literature of
what has been done to test fibers and materials in the past. I will discuss
the criteria for acceptable tests, subsequently.
Initially, the process starts with a material that has promise and retains
the desirable attributes for a particular application or various applications
as a substitute for asbestos. For example, this could be a chemical modifi-
cation of the asbestos surface to allow asbestos to serve as its own
substitute.
If the initial finding is that the material causes severe effects compared
to asbestos, then such material, even though it is desirable, is assigned a
low-priority as a substitute for further in vivo testing. If the effects are
not severe, but the material shows moderate effects, then such material would
be assigned as a medium priority substitute for testing. If there are slight,
or negligible, effects, such material would be assigned as a high priority and
desirable substitute to expend funds for in vivo tests.
In a similar manner for the in vivo tests, if there are severe effects,
then the material may represent a substantial risk requiring more testing and
interim unreasonable risk protection. If there is no substantial risk, under
the TSCA procedures, there would be no need to propose regulations or conduct
further evaluations to determine unreasonable risks. Therefore, that would be
an acceptable substitute.
If there is a determination that the data suggests a substantial risk,
then the TSCA unreasonable risk determination would apply as presented in
Figure 1. If there is essentially a finding that the benefits derivable
656
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DESIRABLE
PROPERTIES
IN VITRO
TESTS
SEVERE
EFFECTS
HP
MODERATE
EFFECTS
YES
YES
NO
IN VIVO
TESTS
HIGH
PRIORITY
SUBSTITUTE
MEDIUM
PRIORITY
SUBSTITUTE
LOW
PRIORITY
SUBSTITUTE
SEVERE
EFFECTS
YES
SUBSTANTIAL
RISK
YES
ACCEPTABLE
SUBSTITUTE
MODERATE
EFFECTS
NO
YES
NO
REGULATION
TSCA
UNREASONABLE
RISK
ASSESSMENT
UNREASONABLE
RISK
PROHIBIT
USE
YES
UNACCEPTABLE
SUBSTITUTE
Figure 2. Decision process for selecting materials to test,
657
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from the use of the substance exceed the cost of allowing its use, then there
is no unreasonable risk, under TSCA. Such a material would be an acceptable
substitute.
When the benefits do not balance the costs associated with use of the
material, that would be a finding of an unreasonable risk and, therefore, an
unacceptable substitute. EPA may decide to prohibit its use, or to exercise
appropriate regulatory options. The administrator may propose regulations
that would allow a social management of the degree of risk to an acceptable
level and, therefore, that would be an acceptable substitute under special
regulatory conditions.
In a similar manner, if there are moderate effects, then there needs to
be a determination of whether those moderate effects represent a substantial
risk, based upon extent of exposure and adverse effects data.
If there is no substantial risk, then there is no need for regulation.
Therefore, that would be an acceptable substitute. If there is a substantial
risk, an unreasonable risk determination is required. The decision process
as to whether to prohibit or to regulate applies, and the material is deter-
mined to be an acceptable substitute or an unacceptable substitute.
This process takes considerable time to obtain approval of a material
with desirable properties. Persuading EPA to allow that material to be used
as an acceptable substitute, involves some rather complex regulatory and
administrative procedures. For new materials, the assessments depend upon
in vitro and in vivo tests in animal systems.
One other point is that in regard to the EPA policy statement on the
regulation of exposures to asbestos, the data used to establish its current
policy is primarily epidemiologic data. In general, in vitro or in vivo
studies are not quoted as direct support for EPA policy, but they are quoted
as providing biological plausability to epidemiologic findings.
In developing information on a new product or a substitute for asbestos,
the epidemiologic data will not be available for most substances. It is
also extremely difficult, on the basis of in vitro tests and in vivo tests,
to predict perhaps the epidemiologic experience of a human population in
20 years or 35 years.
This creates a dilemma for making unreasonable risk decisions. Instead of
having the desirable kinds of information on exposure of humans from epidemi-
ologic data, the characterization of the adverse effects in regulatory decision
making will be necessarily based upon surrogate data. Such data include
production data, proposed geographic distribution of the chemical substance or
agent under review, and extrapolation from available in vitro and in vivo data
to what the adverse effects might be in humans.
*
In trying to determine what kinds of tests one might conduct to be
persuasive to the EPA in its exercise of its regulatory duties to manage or
possibly eliminate, the unreasonable risk from exposure to asbestos or
658
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proposed substitutes, I reviewed various documents — the National Academy of
Science document on asbestos, the Criteria Document from NIOSH, the update of
the Criteria Document, the various publications qf^Federal agencies and^trade
associations, discussing the biological properties and activities of asbestos.
From this review, I prepared a list of the types of in vitro and in vivo
studies that were quoted in support of any regulations, recommendations, and
proposed policy. Very few in vitro studies were used in these documents. Also
a limited number of in vivo studies were quoted in support of the recommenda-
tions in these various documents.
The next step was to review the available literature on the biological
activity of asbestos. Some 180 articles were found. However, very few of
these were quoted in the previous documents that I reviewed. These articles
discussed the biological effects, including the molecular biology and cellu-
lar interactions of asbestos in biological systems. Various in vitro studies
that would be available to serve as tests to evaluate potential substitutes
are listed in Table 1.
Hemolytic activity is a test used to demonstrate the irritation of cell
membranes using red blood cells. The adverse effect of asbestos and other
materials on cell membranes has been commented upon several times during the
workshop. Asbestos and some proposed substitutes irritate membranes and
either cause release of substances from these membranes, in this case, hemo-
globin which serves as its own indicator or actually destroys the integrity
of the cell.
Hemolytic activity or high hemolytic activity of a proposed substitute
would suggest that it is equally active in this particular effect when
compared to asbestos.
There are various cytotoxicity studies concentrating upon macrophages,
fibroblasts, tracheal epithelium slices, and bronchial epithelium slices.
The significance of the macrophage studies is that cytotoxicity in these
cells represents interference with the second line of defense of the body,
and in this case, the lungs. The immobilization of the macrophages or dis-
turbance of the biochemistry of the macrophage, would suggest an interference
with the defense mechanism.
The fibroblast is an important cell in the alveolar wall, and fibro-
blasts are responsible for synthesis of elastic tissues. There is a need for
a certain amount of elastic tissues to maintain the structural integrity of
the lungs, particularly the alveoli.
The tracheal epithelium is a critical target tissue, as is the bronchial
epithelium. These types of cytotoxicity studies are selected on that basis.
Use of critical tissues could provide the basis for design of acceptable
test protocols for evaluation of exposures to asbestos or proposed substitutes.
DNA synthesis is another measure which can be a rather sophisticated
indication of new cell growth. In addition, depending upon the repair rates,
659
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TABLE I
IN VITRO STUDIES
o\
o
TEST
HEMOLYTIC ACTIVITY
CYTOTOXICITY
HACROPHAGES
FlBROBLASTS
TRACHEAL EPITHELIUM
BRONCHIAL EPITHELIUM
DMA SYNTHESIS
ENZYMATIC ACTIVITIES
MUTAGENIC ACTIVITY
MiTOTic RATE
HlSTOCHEMICAL
SIGINIFICANCE
IRRITATION OF CELL MEMBRANES OR LYSIS
OF RED BLOOD CELLS
INTERFERENCE WITH DEFENSE MECHANISMS
IMPORTANT CELL IN THE ALVEOLI WALL
CRITICAL TARGET TISSUE
CRITICAL TARGET TISSUE
INDICATES DEGREE OF NEW CELL GROWTH
INDICATES POTENTIAL IRRITANT EFFECTS
ON MEMBRANES OR SUBCELLULAR STRUCTURES
INDICATES INTERFERENCE WITH THE FLOW
OR EXPRESSION OF GENETIC INFORMATION
INDICATES THE DEGREE OF NEW CELL GROWTH
AND DIVISION
ALLOWS COMPARISONS OF CONTROL CELLS
WITH EXPOSED CELLS
-------
new DNA synthesis could indicate the rate of repair that is going on as a
result of damage.
Enzymatic activities — There are numerous studies where LDH and trans-
aminases have been measured in a supernatant indicating that the substance
under test is an irritant on membranes or subcellular structures.
Mutagenic activities, such as dominant lethal assays, looking at reversal
of mutations on rather exotic kinds of cells, such as Salmonella mutants,
indicate a potential for interference with the flow or expression of genetic
information. This might be a useful test to propose as part of an acceptable
test protocol.
Mitotic studies indicate the degree of new cell growth and division.
There are various chemical studies which allow comparisons of control cells
with cells exposed to a proposed substitute. Based upon the performance of
the material in rapid screening tests, such tests could be used to establish
a priority for conduct of more extensive in vivo tests.
In Table II, the in vivo studies that have been previously reported are
inhalation studies, histochemical studies and tumor yield studies. Inhalation
studies can be classified into short-term exposure tests and long-term exposures.
The short-term exposure tests are usually at high doses and short durations
of exposure. Short-term high dose studies are used to estimate responses in
a short period of time and levels immediately hazardous to life. Extrapolations
beyond the duration of the experiment can be questionable.
Long term exposures are primarily for the lifetime of the animal and
attempt to develop dose response data which allow an improved prediction of
chronic effects.
These kinds of studies, however, because of the long term exposures,
number of animals involved, and the number of doses, are fairly expensive
(as indicated by the studies described for vitreous glass).
Histochemical studies can be characterized into four basic types,
described in the literature. These are carcinogenesis, production of fibrosis,
the release of enzymes which indicates the irritant effects on tissue and
membranes, and the clearance of particles or interference with the clearance
of particles which indicates possible interference with macrophage mobility
and/or interference with phagocytosis of inert particles.
Non-specific immune response studies indicate another level of inter-
action with macrophage cells through having the proposed substitute stimulate
the release of a macrophage factor, thus indicating a generalized immune
response.
Tumor yield studies are perhaps the most significant in terms of
evaluating proposed substitutes. With high positive results, one would have
the greatest degree of unreasonable risk. In these studies, there are often
positive controls where a known carcinogen is given, along with the proposed
661
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TABLE II
IN VIVO STUDIES
O\
N>
INHALATION AND LUNG STUDIES
SHORT TERM EXPOSURES
LONG TERM EXPOSURES
HISTQCHEMICAL STUDIES
COLLAGEN SYNTHESIS
RELEASE OF ENZYMES
CLEARANCE OF PARTICLES
IMMUNE RESPONSE
TUWB YIELD STUDIES
OSITIVE CONTROLS
NEGATIVE CONTROLS
^ARTICLE EXPOSURE ONLY
ARTICLE EXPOSURE WITH
KNOWN CARCINOGEN
ACUTE REPONSES POSSIBLE IN SHORT TIME
DEVELOPMENT OF DOSE RESPONSE DATA AND
IMPROVED PREDICTION OF CHRONIC EFFECTS
NDIGATES POTENTIAL TO PRODUCE FIBROS IS
NDICATES POSSIBLE IRRITANT EFFECTS ON
ISSUES AND MEMBRANES
NDICATES POSSIBLE INTERFERENCE WITH
MACROPHAGE MOBILITY AND/OR PHAGOCYTOSIS
INDICATES POSSIBLE STIMULATION OF
MACROPHAGE FACTOR TO INDUCE IMMUNE RESPONSE
[NDICATES VALIDITY OF TEST SYSTEM
•STABLISHES BASELINE FOR COMPARISONS
NDICATES POTENTIAL FOR DIRECT CARCINOGENISIS
INDICATES POTENTIAL TO PROMOTE CARCINOGENISIS
-------
substitute. This approach indicates the validity of the test system. If the
agent under test is capable of producing cancer, the system would detect that
there is an increase in tumor yield, or that there are cancers.
f
There is also a need for use of inert fibers in studies to establish
a baseline for ratios of tumor yields to compare with the effects of various
proposed substitutes. Other protocols that have been used are particle
exposure only and particle exposure with a known carcinogen. These protocols
are intended to look at either direct carcinogenesis by the substance or look
at the potential to promote carcinogenesis.
This brief perusal of the available literature has led to six criteria
in Table III for biological tests for evaluation of proposed asbestos
substitutes. The first criteria is that the experimental protocol must
include both positive and negative control for comparisons of toxic effects.
Secondly, a range of doses should be used which are sufficient to define
dose response. There has been some discussion during the workshop that there
is a threshold below which the body can defend itself against asbestos and
other fibrous materials. However, the current risk assessment approach,
particularly for carcinogenic substances is that the dose response is a linear
or non-threshold relationship.
The statistical design of the test must be adequate to analyze all
identified sources of variation, and to estimate confidence intervals. A
fourth extremely important criteria for the testing system is-that the
chemical purity and physical characteristics of the material under test must
be determined. This is extremely important in dealing with a complex material
such as asbestos because a material characterized as chrysotile, for example
can come from a variety of sources in the world. Chrysotiles from various
sources have different chemical compositions and different physical
characteristics in terms of particle size, fiber diameter, and fiber lengths.
A chrysotile from Cassiar, for example, does not appear to be as active in
certain kinds of tests as a chrysotile from a South African mine or a
chrysotile from the eastern portion of Canada.
The biological variables must be clearly defined as specified. This
includes variables such as the animal species and diet. All essential factors
must be specified so that one can reproduce the test and make comparisons
between tests performed at different laboratories or using different materials.
Finally, the tests should include provisions for independent verification
of results by other investigators, this could be by use of an independent
test system, or the use of more than one species to verify that this is a
general biological response rather than a species' specific type of response.
We are interested in developing a set of acceptable test protocols so
that in two or three years we can submit appropriate data to the Environmental
Protection Agency to register what we think is a viable substitute for asbestos,
The biological data, if positive in indicating a lack of biological activity
663
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TABLE III
CRITERIA FOR BIOLOGICAL TESTING OF PROPOSED ASBESTOS SUBSTITUTES
1, THE EXPERIMENTAL PROTOCOL MUST INCLUDE BOTH POSITIVE AND NEGATIVE CONTROLS
FOR COMPARISONS OF TOXIC EFFECTS.
2, A RANGE OF DOSES SUFFICIENT TO DEFINE DOSE-RESPONSE IS RECOMMENDED.
3. STATISTICAL DESIGN OF THE TESTS MUST BE ADEQUATE TO ANALYZE IDENTIFIED
SOURCES OF VARIATION AND TO ESTIMATE CONFIDENCE INTERVALS.
1, THE CHEMICAL PURITY AND PHYSICAL CHARACTERISTICS OF THE MATERIAL UNDER
TEST MUST BE DETERMINED,
5. BIOLOGICAL VARIABLES MUST BE CLEARLY DEFINED AND SPECIFIED.
6. TESTS SHOULD INCLUDE PROVISIONS FOR INDEPENDENT VARIFICATION OF RESULTS
BY OTHER INVESTIGATORS, USE OF A SIMILAR TEST SYSTEM, OR USE OF OTHER
SPECIES.
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or an acceptable level of biological risk must be persuasive to the regulatory
decision makers in the EPA. This approach would allow our proposed substitute
or others to be distributed, used, and manufactured in the United States.
•D.«. OOVBONBrC PEtBTUKJ OJTICE : 1981 O-73V506/901
665
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