GCA-TR-79-7 3-G
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Toxic Substances
Washington, D.C.
Submitted in Partial Fulfillment of
Contract No. 68-02-3168
Technical Service Area 3, Work Assignment No. 18
EPA Project Officer
James Bulman
LIFE CYCLE OF ASBESTOS IN COMMERCIAL
AND INDUSTRIAL USE INCLUDING ESTIMATES
OF RELEASES TO AIR, WATER AND LAND
Final Inhouse Report
February 1982
Prepared by
David Cogley
Nancy Krusell
Robert Mclnnes
Peter Anderson
Ronald Bell
GCA CORPORATION
GCA/TECHNOLOGY DIVISION
Bedford, Massachusetts
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DISCLAIMER
This Final Inhouse Report was prepared for the Environmental Protection
Agency by GCA Corporation, GCA/Technology Division, Burlington Road, Bedford,
Massachusetts 01730, in partial fulfillment of Contract No. 68-02-3168,
Technical Service Area 3, Work Assignment Nos. 2 and 18 and Contract
No. 68-02-2607, Work Assignment No. 36. The opinions, findings, and
conclusions expressed are those of the authors and not necessarily those of
the Environmental Protection Agency. Mention of company or product name is
not to be considered as an endorsement by the Environmental Protection Agency.
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CONTENTS
Figures vi
Tables viii
1. Introduction 1
Overview 1
Report Format 3
Data Presentation 3
Terminology 5
References 7
2. Air Pollution Control Practices, Asbestos Emissions, and Asbes-
tos Exposure 8
Introduction 8
Control Techniques 8
Waste Disposal 11
Human Exposure to Asbestos 14
Conclusion 23
References 25
3. Mining and Milling of Asbestos 27
Introduction 27
Asbestos Mining 28
Asbestos Milling 33
Environmental Regulations and Compliance 35
Atmospheric Emissions from Mining and Milling 36
Ambient Asbestos Fiber Concentrations ..... 38
Nonoccupational Atmospheric Exposure 38
References 39
4. Asbestos Paper Products 41
Introduction 41
Product Descriptions 42
Substitutes 50
Manufacturing 54
Asbestos Release 62
Conclusion ....... ..... 72
References 77
5. Friction Materials 82
Introduction 82
Product Description 84
Substitutes 88
Manufacturing 92
Asbestos Release 98
Conclusion 110
References Ill
iii
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CONTENTS (continued)
6. Asbestos-Cement Pipe 115
Introduction 115
Product Description 117
Substitutes 118
Manufacturing 119
Asbestos Release 122
Conclusion 131
References 132
7. Asbestos-Cement Sheet 135
Introduction 135
Product Description 135
Substitutes 138
Manufacturing 140
Asbestos Release 146
Conclusion 151
References 153
8. Flooring Products 155
Introduction 155
Product Description 155
Substitutes 157
Manufacturing 157
Asbestos Release 161
Conclusion 167
References 169
9. Gaskets and Packing. 171
Introduction 171
Product Description 171
Substitutes 175
Manufacturing 176
Asbestos Release 181
Conclusion 185
References 186
10. Sealants 189
Introduction 189
Product Description 189
Substitutes 191
Manufacturing 193
Asbestos Release 197
Conclusion 202
References 204
11. Asbestos-Reinforced Plastics 206
Introduction 206
Product Description 206
Substitutes 208
Manufacturing 210
Asbestos Release. . 214
Conclusion 219
References 221
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CONTENTS (continued)
12. Textiles 223
Introduction 223
Product Description 223
Substitutes 227
Manufacturing 231
Asbestos Release 234
Conclusion 239
References 241
13. Miscellaneous Asbestos Uses 245
Introduction 245
Drilling Muds 245
Shotgun Shell Base Wads 249
Asphalt/Asbestos Cement 250
Foundry Sands 250
Sprayed-on Insulation 250
Artificial Fireplace Ashes and Artificial Snow 251
Conclusion 251
References 255
14. Results, Discussion and Conclusion 258
Results 258
Discussion and Conclusion 262
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FIGURES
Number Page
1 Asbestos-containing waste disposal treatment options 13
2 Asbestos paper manufacturing operations 55
3 Asbestos paper saturation 58
4 Asbestos millboard manufacture 60
5 Input/output estimates for the asbestos paper industry (metric
tons) 64
6 Dry-mixed molded brake lining manufacture 93
7 Wet-mixed molded brake lining manufacture 94
8 Molded clutch facing manufacture 96
9 Woven clutch facing manufacture 97
10 Input/output estimates for the asbestos friction materials
industry in metric tons 101
11 U.S. A/C pipe imports in millions of pounds of pipe 116
12 Manufacture of asbestos-cement pipe 120
13 Flow diagram of asbestos-cement pipe manufacturing operations
by the wet mechanical process 121
14 Input/output of asbestos disposal and emissions for the asbes-
tos cement pipe industry (metric tons) 124
15 Asbestos-cement sheet manufacturing operations, dry process . 141
16 Asbestos-cement sheet manufacturing operations, wet process . 142
17 Asbcstos-cement sheet manufacturing operations, wet mechanical
process 144
18 Input/output of asbestos in the asbestos cement industry
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FIGURE (continued)
Number Page
19 Floor tile manufacturing operation 158
20 Process and disposal emissions (in metric tons) vinyl-asbes-
tos floor tile industry 162
21 Asbestos gasket process operations 177
22 Asbestos packing process flow diagram 178
23 Disposal and emissions of asbestos from the packing and gas-
kets industry (metric tons) 182
24 Process flow diagram for the manufacture of paints, coating,
and sealants 195
25 Input/output estimates for the asbestos sealants industry
(metric tons) 198
26 General process flow for manufacture of asbestos-reinforced
plastic 211
27 Process and disposal emissions from asbestos plastics in-
dustry (metric tons) 215
28 Strength retention of plain (nonmetallic) asbestos textiles
after 24-hour exposure to temperatures of 400°, 600°, and
800°F (190; 280; 380°C) 228
29 Manufacturing operations for asbestos textiles 232
30 Process and disposal emissions (in metric tons/year) for
asbestos textiles 235
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TABLES
Number Page
1 Asbestos Products Industry ... 2
2 1 980 Asbestos Consumption by Product Category 4
3 Conversion Factors 6
4 Use of Emission Control in Asbestos Products Manufacturing
Plants, 1974 10
5 Bureau of Mines Asbestos Consumption Data, By Product Category,
1976-1978-1980 16
6 Atmospheric Exposure to Asbestos in the Vicinity of Asbestos
Industrial Facilities 19
7 Airborne Asbestos Emissions from Process and Disposal -
Primary Industry 21
8 GCA Estimates of Fiber Release from Manufacturing and
Disposal - 1980 22
9 American Asbestos Mines and Mills 29
10 Asbestos Fiber Exposure in Mines (Time-Weighted Average) ... 31
11 Asbestos Fiber Exposure in Mills (Time-Weighted Average) ... 34
12 Asbestos Emissions to Air from Mining and Milling (1974) ... 37
13 Estimated Use of Asbestos Fiber in Paper Products - 1979 ... 42
14 Industries Using Asbestos Millboard and Individual
Applications 45
13 Principal Manufacturers of Asbestos Paper 61
16 Time-Weighted Average Fiber Counts - Asbestos Paper Products . 65
17 Ambient Asbestos Fiber Levels Reported by Johns-Manville for
Sampling Done in 1969-1971 ..... 69
18 Sampling Results of an Asbestos Paper Plant (1979) 70
viii
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TABLES (continued)
Number Page
19 Value of Asbestos Friction Material Shipments (in millions
of 1981 dollars) 83
20 Average Brake Lining Composition (Weight Percent) 85
21 Brake Lining Compositions from Patent Literature (Weight
Percent) 85
22 Property Modifiers in Friction Materials 86
23 Unique Properties of Asbestos Applicable to Friction Materials 88
24 Composition of an Asbestos-Free Disc Brake Pad (in volume
percent) 91
25 U.S. Manufacturers of Asbestos-Bearing Friction Materials. . . 99
26 Time-Weighed Average Fiber Concentrations of Optical Micro-
scope Visible Fibers Greater Than 5 pm in Friction Products
Manufacturing Plants 100
27 Summary of Published Data - Asbestos Emissions from Brake Lining
Use. 106
28 Asbestos Fiber Exposure Levels in Rebuilding Brake and Clutch
Assemblies 109
29 Fiber Levels During Brake Lining Maintenance 109
30 Location and Sales of Major A/C Pipe Plants 123
31 Asbestos-Cement Pipe Manufacture - Asbestos Exposure Levels. . 125
32 Representative Fiber Count Values Obtained at Three Asbestos
Waste Dumps (from Harwood and Oestreich) 128
33 Distribution of Reported Asbestos Concentrations in Drinking
Water from 365 Cities, 43 States, Puerto Rico, and the
District of Columbia 129
34 Shipment Values of Asbestos-Cement Sheets, Including A/C Roof-
ing Products 136
35 A/C Sheet Asbestos Consumption in 1980 (Metric Tons) 136
36 Major Manufacturers of Asbestos-Cement Sheet 145
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TABLES (continued)
Number Page
37 Measured Time-Weighted Average Fiber Counts During the Manufac-
ture of Asbestos-Cement Sheet 148
38 Formulation for a Vinyl-Asbestos Floor Tile 156
39 Major U.S. Manufacturers of Asbestos Flooring 160
40 Time-Weighted Average Fiber Counts Floor Tile 163
41 Asbestos Used in Gaskets and Packings (1980) 172
42 Comparative Properties of Elastomers 173
43 Elastomer Classifications 173
44 U.S. Asbestos Gasket and Packing Manufacturers . . . 180
45 Existing Fiber Counts. . 181
46 Distribution of Asbestos Minerals Used for Coatings, Paints,
and Sealants (1980). . 190
47 Physical and Resistant Characteristics of Coating and Sealant
Materials 193
48 National Manufacturers of Asbestos Sealant Products . 196
49 Time-Weighed Average Fiber Counts-Paints, Coatings, and
Sealants 200
50 Approximation of Asbestos Released to Environment from Coating
and Painting Compound Applications . . 203
51 Asbestos Use by Type and Grade in 1980 207
52 Typical Changes In Resin Properties with Asbestos
Reinforcement 207
53 Asbestos Substitute Materials 209
54 Primary Manufacturers of Phenolic Molding Compounds 210
"35 Time-Weighted Average Fiber Counts - Asbestos-Reinforced
Plastics 216
56 Forms of Asbestos Textiles Used in Asbestos Products 224
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TABLES (continued)
Number Page
57 Asbestos Textile Grades 224
58 Asbestos and Substitute Material Property Comparison for
Textile Products 229
59 Manufacturers of Asbestos Textiles 234
60 Time-Weighted Average Fiber Counts - Asbestos Textiles 236
61 Airborne Asbestos in Buildings 252
62 Asbestos Release Potential 260
63 Exposure Data (Typical fibers/cc TWA) - 1975 263
64 GCA Estimates of Asbestos Release from Manufacturing and Dis-
posal to Air, Water and Land, in Mt/yr - 1980 265
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SECTION 1
INTRODUCTION
OVERVIEW
Asbestos is a generic term for a group of fibrous minerals chat are
used in many industrial, commercial and household products. Asbestos provides
strength, durability, resilience, chemical and thermal stability, and resist-
ance to heat, corrosion, rot, vermin and chemicals. An average United States
resident could expect to find asbestos around his home contained in the following
products: floor tile, house siding, automobile brakes, appliance insulation,
roof flashing compound, municipal water supply pipe, sewer mains, wood stove
gaskets and fireproofing for wood stove installations. For every U.S. citizen,
approximately 1.6 Kilograms (3.6 lbs) of asbestos is used to manufacture products
annually.
Asbestos pri>dui.-ts reach the consumer after passing through several
manufacturing and fabrication steps. These steps are most easily understood
by examining the asbestos products industry. This industry has been cate-
gorized into the following three groups:2
• Primary Industries: those industries which r.tart the manufacturing
process with raw asbestos fiber and modify the fiber to produce an
intermediate product (to be further processed or fabricated) or a
finished product.
• Secondary Industries: those industries w'ach continue the manufac-
turing process with an intermediate asbestos product (one in which
the fiber has previously been modified in a primary industry) and
further process, modify, or fabricate it to produce either another
intermediate product (to be further processed or fabricated) or a
finished product.
• Consumer Industries: those industries which purchase a finished
asbestos-containing product (From a primary or secondary industry)
and apply, install, eri'ct, or consume the asbestos-containing
product without furirh'sr physical modification of the product.
Table 1 presents a classification of the various industries and indi-
cates the interrelationship of the three groups.
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Primary Industry
TABLE 1. ASBESTOS PRODUCTS INDUSTRY3
Secondary Industry Consumer industry
Asbestos paper
Friction products
Adhesion cement pipe
Asbestos - cement sheet
floor tile
i.oskets nnd packing
Fireproof absorbent papers
Table pads end heat protective mats
Heat/firs protection components
Insulation products
Underlayment for sheet flooring
Filters lor beverages
Rooflng materials
Clutch/transmission, brake components
Industrial friction materials
Chemical process piping
Water supply piping
Conduits for eleccrlc wires
Hoods, vents for corrosive chemicals
Portable construction buildings
Molten octal handling equipment
Industrial building materials
Laboratory furniture
Cooling tower components
Office, home, commercial floors
Valve, flange, pump, tank
sealing components
AutomuiIve/lruck body coatings
Roof coatings and patching compounds
4*be»i'
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REPORT FORMAT
This report describes the life cycle of asbestos from mining and milling
the raw mineral through its ultimate use and disposal by the consumer. Following
a discussion of mining and milling operations, the remaining sections of the
report are organized by primary industry in descending order based on asbestos
consumption. The main thrust of the report is identifying releases of asbestos
fibers to the air, water and land during manufacture, use and ultimate disposal
of the mass-produced product. Estimates are provided of worker exposure levels
and ambient asbestos levels in the vicinity of primary industry plants. Each
primary industry is discussed in detail. Asbestos products, their composition,
uses, substitutes and manufacturing processes are described with special attention
given to the handling and disposal of asbestos. The roles of secondary and
consumer industries are addressed when specific asbestos-related information is
available. The conclusion segments found at the end of each section encompass
projections and trends as well as a summary of information on the product discussed.
DATA PRESENTATION
Data presented herein were obtained from published reports. These were
augumented by telephone calls and plant visits to obtain further information on
manufacturing operations, industrial asbestos consumption, pollution control
devices, manufacturing facility asbestos emissions, industry trends, substitute
products and exposure data for workers aid product users. Some new monitoring
data were obtained for presentation in this report.
Asbestos consumption data in metric tons, along with the relative percentage
breakdown for each primary industry are presented in Table 2. These data were
extracted from the 1980 Bureau of Mines (BOM) survey, which is based on an annual
survey of domestic raw-asbestos fiber consumers. The number of manufacturers
responding to the BOM survey, approximately 300, account for 60 percent of the
total annual domestic asbestos consumption.1* The values reported represent an
extrapolation of the 60 percent figures received by BOM up to 100 percent consump-
tion. Consequently, there is some inherent uncertainty, which U.S. BOM estimates
to be + AO percent, associated with the reported values. The individual product
categories in Table 2 differ slightly from those reported by the BOM. For this
report, the paper category includes paper products, thermal and electrical insu-
lation, and roofing products. In addition, that portion of the flooring products
asbestos consumption which is attributable to flooring felt (approximately 60
percent),5 has also been defined here as "paper products." These changes were
made to consolidate the presentation and to group together all products that are
manufactured by conventional paper making equipment.
There exists a great body of worker exposure data gathered in response
to OSHA regulations. These data, when summed over the known labor force,
provide a limited estimate of worker exposure in mining, milling, manufacturing,
and in some cases product installation. Alternatively, a limited amount of
exposure data for products are available. Exposure to persons living or
working near mines, mills, manufacturing facilities, and end-use locations
was difficult to assess accurately because of the limited amount of ambient
monitoring data available. However, nonoccupational exposure has been estimated
using air quality dispersion models in conjunction with assumed emissions.
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TABLE 2. 1980 ASBESTOS CONSUMPTION BY PRODUCT CATEGORY3
1980 Consumption Percent of
Product category (metric tons) 1980 Consumption
Asbestos cement pipe
144,000
40.2
Asbestos paper
90,020
25.1
Friction products
43,700
12.2
Floor tile
36,080
10.1
Gaskets and packing
12,300
3.4
Coating and sealants
10,900
3.0
Asbestos cement sheet
7,900
2.2
Textile
1,900
0.5
Plastics
1,500
0.4
Miscellaneous
10,400
2.9
Total
358,700
100
GCA product category designations.
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There is also a scarcity of data concerning process emissions from primary
asbestos industry facilities. Due to OSHA regulations, many primary plants
have installed fabric filters at the principal fiber introduction areas.
Estimates of how much asbestos fiber is released to the filters at these sta-
tions vary depending on the amount of asbestos introduced into the manufacturing
process, the conditions of the ventilation system, the method of processing,
i.e. wet or dry, and the employment of dust inhibiting materials or operations.
Similarly, the amount of product scrap and control device waste that is generated
by a facility varies considerably among manufacturers. Finally, asbestos users
are generally reluctant or unable to estimate these waste amounts. In addition,
published estimates on waste quantities for primary industries vary consider-
ably.^'^ As a result, the emission estimates cited in this report are, at best,
order of magnitude estimates.
TERMINOLOGY
In this report atomspheric asbestos concentrations are reported in terms
of:
• Optical-microscope-visible fibers per cubic centimeter (fibers/cc)
for fibers longer than 5 un.
• Optical-micro.scope-visible fibers per cubic meter (fibers/m3) for
fibers longer than 5 ym.
• Electron-microscope-visible fibers per cubic centimeter (fibers/cc)
• Klectron-microscope-visible fibers per cubic meter (fibers/m3).
• Nanograms of asbestos per cubic meter (ng/m3).
Table 3 shows conversion factors that can be multiplied by concentrations
expressed as optical-microscope-visible fibers/cc to yield a concentration
expressed in the units desired. In developing these figures it was assumed
that:
There are 50 electron-microscope-visible fibers for every
opticai-microscope-visible fiber greater than 5 Mm in
length.^
There are 1,000 electron-microscope-virible fibers per
nanogram although the actual conversion may be from 100
to 10,000 fibers/ng^ The conversion factors presented in
Table 3 are useful for the preparation of first order
estimates only. Asbestos fiber size distribution varies
with the grade of fiber used and the extent of processing
during manufacture and product use.
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TABLE 3.
CONVERSION FACTORS7
Optical-microscope-
visible fibers/cc
> 5 pin in length
Optical-microscope-
visible fibers/tn3
> 5 pm in length
Electron-microscope-
visible fibers/cc
Electron-microscope-
visible fibers/m3 ng/m3
la
1,000,000
50
50,000,000 50,000
Values shown are all equivalent to 1 optical-raicroscope-visible fiber/cc > 5 pi in length.
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REFERENCES
1. Clifton, R. A., Asbestos. 1980 Minerals Yearbook, U.S. Bureau of Mines,
Washington, D.C., 1981.
2. Daly, A. R., A. J. Zupko and J. L. Hebb. Technological Feasibility and
Economic Impact of OSHA Proposed Revision to the Asbestos Standard
(Construction Excluded), prepared for Asbestos Information Association/
North America, Washington, D.C., 29 March 1976.
3. 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.
4. Telecon. R. A. Clifton. U.S. Bureau of Mines, Washington, D.C., with
Peter Anderson, GCA/Technology Division. October 8, 1981.
5. The Resilient Floor Covering Institute. Comments on the Advanced Notice
of Proposed Rulemaking on the Commercial and Industrial Use of Asbestos
Fibers. Submitted to the U.S. EPA, Washington, D.C. February 18, 1980.
6. Meylan, W. M., P. H. Howard, S. S. Lande and A. Hanchett, Chemical Market
Input/Output Analysis of Selected Chemical Substances to Assess Sources
of Environmental Contamination: Task III. Asbestos. EPA-560/6-78-005,
U.S. Environmental Protection Agency. Washington, D.C., August 1978.
7. Suta, B. E., and R. S. Levine. Non-occupational Asbestos Emissions and
Exposure. In: Asbestos, Volume I, Properties, Applications, and Hazards,
L. Michaels and S. S. Chissick, eds. John Wiley & Sons, New York, N.Y.
]979. pp 171-205.
7
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SECTION 2
AIR POLLUTION CONTROL PRACTICES, ASBESTOS
EMISSIONS, AND ASBESTOS EXPOSURE
INTRODUCTION
The dangers associated with asbestos exposure combined with regulatory
policies concerning asbestos have prompted asbestos mining, milling and manu-
facturing industries to employ a variety of measures to reduce human exposure
to asbestos fibers. These measures include such techniques as enclosure of
asbestos fiber transfer points, the ducting of airborne asbestos from these
enclosures to air pollution control devices and the subsequent disposal of
the captured asbestos. This section presents ari overview of these control
techniques and disposal methods.
In a,id it i«hi, estimates of the amount of asbestos released to the air from
process and disposal operations will be reviewed in this section. These
esctmates are based on studies performed by two independent researchers.*
Their work will be reviewed in detail and both occupational and nonoccupational
exposure levels will be discussed. These studies used air emission estimates
in conjunction with mathematical dispersion mode Ls to predict ambient asbestos
concentrations in the vicinity of primary asbestos manufacturing facilities.
These predicted concentrations will also be discussed and compared to actual
ambient asbestos concentrations measured by the Connecticut Department of
Environmental Protection.^ Finally, GCA evaluated all asbestos release
iin-innation and prepared its own estimates on asbestos fiber releases to the
environment. These estimates will be summarized in this section.
CONTROL TECHNIQUES
Asbestos Mining and Milling
n it* raining of asbestos-bearing rock can be a primary source oi* airborne
asbestos fibers, although emission controls exist for each process in this
operation. Malor sources of asbestos emissions from mining operations include
drilling, blasting, road dust and ore dumping, crushing and transportation.
Bae filters can be attached to mobile drilling units to control emissions
during this process. The need for filtering devices has been eliminated in
instances by using a wet drilling procedure. Emissions during blasting
are largely uncontrolled but may be reduced somewhat by wetting the surface
8
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around the blast site with water or a chemical wetting agent. Road dust is
often controlled by using sprays of water with and without chemical additives
or by using a spray of oil. Once rained, ore is dumped into a "dumping pit"
which feeds the ore into a crusher to reduce the particle size.^ To control
emissions the pit can be enclosed while the crusher can be hooded and vented
to a baghouse. Emissions during loading can be controlled by wetting the ore
while loading and unloading trucks, or by loading and unloading in emission-
controlled enclosures.^ Emissions during trucking can be controlled by using
closed bodied trucks or flexible impervious covers.^ At present, however,
the extent to which emission controls are applied in the mining of asbestos
is largely unknown.
In the milling operation asbestos is separated from the accompanying rock.
Sources of emissions include ore stockpiles, ore dryers, hamraermills, crushers
vibrating screens, belt conveyors and automatic bagging machines. Water is
often sprayed onto ore stockpiles to control emissions. Hammermills, crushers,
vibrating screens and bagging machines are hooded and vented to a central bag-
house. Belt conveyors are usually completely enclosed to prevent emissions.
Transfer points where ore, asbestos fiber and asbestos-containing waste prod-
ucts are transferred from conveyor systems to plant operations are hooded and
vented to a baghouse.J Cyclones are commonly used in ore-drying operations
due to their relative insensitivity to process gas changes in temperature and
humidity. The major disadvantage of cyclone filters is their poor efficiency,
which is about 70 percent for asbestos fibers. By using multiple small
cyclones to replace one large cyclone the efficiency can be increased to about
90 percent.-'
Asbestos Manufacturing Industries
Several potential sources of asbestos emissions in the asbestos manufac-
turing industries can be identified. In the fiber receiving and storage area,
broken bags and spills account for most of the fiber release. Control prac-
tices in this area include pelletizing shipments, shrink-wrapping pallets,
repairing broken bags, vacuuming spills and receiving asbestos in pelletized
or compressed block form. Manufacturing operations which have a high poten-
tial Tot' emissions include blending, mixing, forming, rolling, and finishing.
In the friction materials industry, finishing operations generate the greatest
quantity of emissions with as much as 30 percent of the asbestos in the product
being ground away as dust.-* Hoods and enclosures are used extensively through-
out the plants to control emissions. Hoods of either a low-volume, high-
velocity or high-volume, low velocity design are used depending on the parti-
cular manufacturing process. Low-volume, high-velocity hoods maintain a face
velocity of between 3050 and 3650 meters per minute (10,000 and 12,000 feet
per minute) while high-volume, low-velocity hoods maintain a face velocity ot
at least 46 meters per minute (150 feet per minute.)3 The high-velocity hoods
are used with machining equipment, such as saws and drills where the release
of particles is localized. High-volume, low-velocity hoods are used to vent
equipment such as mixers and bag opening stations where localized capture is
not possible. In most cases the hoods and associated ductwork tie into a
centralized gas-cleaning device.5'6
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Baghouaes are the most common air pollution control devices used in the
asbestos industries. In a monitoring study of 5 different asbestos emission
sources removal efficiency was found to exceed 99.99 percent.'' Although the
efficiency wan high, measurable quantities of small asbestos fibers were
still released. Fiber concentrations of air exiting the baghouses were found
to be between 1.1 x 107 and 3.3 x 10^ f/m3 for fibers greater than 0.06 ijm in
Length
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WASTE DISPOSAL
Ashes Los Milling Waste Disposal
Compared to asbestos manufacturing plants, asbestos mills generate vast
quantities of waste. Whereas a large manufacturing plant may need a 3-acre
silt- to dispose of Its waste, a tailings disposal site for a large mill
occupies about 100 acres. In 1974 approximately 67 percent of all asbestos
emissions were thought to have originated from mining and milling operations
and disposal with the majority of these emissions coming from mill tailing
disposal sites.* Emissions from mining and milling have probably since
decreased due to new regulations although no supporting monitoring data pre-
sently exists. The asbestos content of mill tailings varies greatly between
different plants with values of 1 to 30 percent asbestos being reported.1
Unlike most manufacturing plants, mills use on-site disposal of waste.
Extensive conveyor systems, with numerous transfer points are used to trans-
port waste tailings from the mill to a disposal area. EPA regulations require
that there be no visible emissions from conveying or disposal of the waste and
that tailings be wetted before disposal (40 CFR 61.22(u)). Emissions can be
minimized by wetting the waste before transporting it from the mill and by
using completely enclosed conveyors. Active disposal sites for mills are
subject to the same regulations (40 CFR 61.25) as asbestos manufacturing
industries.
Inactive sites, in which mill tailings were disposed, may be covered with
15 cm (6 inches) of nonasbestos containing material and a cover of vegetation
(40 CFR 61.22(L)(5)(i), or with at least 61 cm (2 feet) of compacted nonasbestos
containing material (40 CFR 61.22(L)(5)(ii)), or with a resinous or petroleum-
based dust supression agent which effectively binds duSt and controls wind
erosion (40 CFR 61.22(L)(5)(iii)). Although a cover of soil and vepetation
Is the most desirable means of emissions control it is often impractical at
mill tailing disposal sites. The large area occupied by these sites makes
tho cost of soil prohibitive while the high alkalinity of the tailings makes
if difficult to grow vegetation. Erosion is generally controlled at these
sites bv applying chemical dust supression agents. These agents bind the
dust and waste together, forming a crust which resists wind and water
erosion.^ Only short to moderate term stabilization is possible using these
chemicals with reapplication being necessary every 1 to 3 years.^
Asbestos Manufacturing and Fabrication Industries
Asbestos manufacturing operations present potential waste disposal prob-
lems. Asbestos-containing waste is often generated in the form of product
scraps, and as general housekeeping waste which includes floor sweepings,
empty shipping bags and vacuum cleaner bags. Tn most plants, the majority of
waste is in the form of dust collected in baghouse filters.
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Handling and disposal procedures vary with the type of waste generated.
Figure I depicts various asbestos-containing waste disposal treatment
options. AabestoB-cuntaining 9crap products are generated in both friable
and nonfriable form. Nonfriable scraps are not likely to cause atmospheric
emissions since the asbestos fibers are encapsulated by a binding agent and
may be disposed of as is, without any special handling. Some scraps, such
as floor tile and paper scraps can be ground up and fed back into the head
end of the production process. Friable asbestos material as defined by EPA
regulation (40 CFR 61.21(k)) means any material that contains more than 1 per-
cent asbestos by weight and that can be crumbled, pulverized, or reduced to
powder by hand pressure. Before disposal, friable asbestos-containing scraps
should be placed in plastic bags, then tied and marked to indicate the asbes-
tos contents. Alternately, friable materials can be wetted and sealed in
barrels or drums. All asbestos-containing waste scraps should be isolated
from other forms of waste.
Vacuum cleaner dust is the major form of asbestos-containing waste gen-
erated by general housekeeping practices. This waste should be placed into
plastic bags and be kept separate from nonasbestos containing waste. The
bags should be securely sealed and marked to indicate the contents, finpty
shipping bags should also be bagged, tied and marked before disposal. In some
cases, such as in the floor tile industry, empty shipping bags are fed into
the production line and are incorporated into the product.
Baghouse filters are the most common pollution control devices used in
the asbestos manufacturing industries and at most plants they generate the
greatest quantity of asbestos-containing waste. In some cases baghouse dust
is wetted and handled as a slurry. As a slurry, the waste can be pumped into
a tank truck and hauled in bulk shipments. Alternatively, the baghouse catch
can be wetted and placed in leak-tight containers, such as 55 gallon drums (40
CFR 61.22 (j)(4)(B)). The potential for emissions can be minimized by using
lined drums. The baghouse catch can also be mixed with cement to form solidi-
fied, nonfriable pellets (40 CFR 61.22 (j)(4)(C)(ii)) which can be hauled in
open trucks. In some industries the baghouse dust is recycled to the head
end of the process, such as is done in the manufacture of roof coatings. As
many as 6 plants are thought to be using wet scrubbers to control emissions.®
Waste from scrubbers is handled as a slurry. The waste is generally pumped
into tank trucks and hauled to disposal sites.
Asbestos-containing wastes are defined under the National Emission
Standards for Hazardous Air Pollutant (NESHAPs) Program as being hazardous
(40 CFR 61.21). EPA regulations require that no visible emissions be generated
during transportation (40 CFR 61.22 (j)) or from disposal (40 CFR 61.25 (a))
of asbestos-containing waste. Regulations also require that asbestos-
containing waste be covered with at least 15 cm (6 in.) of compacted nonasbestos
containing material (40 CFR 61.25 (e)(1)) or be covered with a resinous or
petroleum based dust supressing agent which effectively binds dust and con-
trols wind erosion (40 CFR 61.25 (e)(2)). If the disposal site is in compli-
ance with the above regulation, the disposal site is not required to employ
warning signs and fencing (40 CFR 61.25 (d)).
12
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WASTE FINES FROM AIR POLLUTION
CONTROL DEVICES AND SECONDARY FABRICATION
ACCUMULATE
SLURRY
BAG
PELLETIZE
WET
PIPE
ACCUMULATE
SETTLING
POND
TRANSPORT
RECYCLE
WATER
TO PROCESS
DUMP, ACTIVE PILE
CHEMICAL
SUPPRESSION
SOIL COVER
WATER SPRAY
* INACTIVE PILE
SOIL COVER"*
AND
EVEGETATION
Figure 1. Asbestos-containing waste disposal treatment options.^
13
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Asbestos-containing waste should be handled carefully and be kept separate
from other waste. The disposal site should be notified before the waste is
sent so that a trench can be dug into which the waste will be unloaded.
Asbestos-containing wastes are unloaded into trenches either in bags, barrels
or as a slurry. The waste should then be immediately covered with soil to
prevent reentrainnsent of the asbestos by the wind. Compaction of the cover should
be minimized to prevent bag breakage when waste is disposed of in plastic bags.
InacLive waste disposal sites are those sites in which additional
asbestos-containing material will not be deposited and in which the surface
will not be disturbed by vehicular traffic (40 CFR 61.17 (t)). Emissions
from these sites can be controlled either by covering with at least 15 cm (6 in.)
of compacted nonasbestos containing material and a cover for vegetation (40
CFR 61.22 (L)(5)(i)) or by covering with at least 61 cm (2 feet) of compacted
nonasbestos containing material and maintained to prevent exposure of the
waste (40 CFR 61.22 (L)(5)(ii)). Vegetation is in most cases the most desir-
able cover since it requires little or no maintenance and serves to reduce
both water and wind erosion.
Before the present standards for the disposal of asbestos-containing
wastes were adopted in 1975, waste dumps were a common means of disposal. A
study In 1974^ showed that 37 percent of all asbestos product manufacturers
disposed of asbestos-containing waste in dumps while only 13.4 percent used
sites which would be acceptable under present standards. Several studies
made prior tu 1975 have shown atmospheric asbestos emissions from dumps to be
very high, approaching occupational levels in the worst cases.' Although no
studies have been conducted since 1975 it should be safe to assume that emis-
sions from disposal have decreased as more stringent asbestos control regula-
tions have been adopted.
HUMAN EXPOSURE TO ASBESTOS
Introduct lori
In this section available data on asbestos exposure in the working
and ambient environments is summarized. Elevated levels of asbestos
fibers in the working environment have long been recognized as a serious prob-
lem. Workplace fiber concentrations of between 0 and 30 optical-microscope-
visible fibers per cubic centimeter (f/cc) have been documented in numerous
studies. As a result, worker exposure can be quantified with a fair degree
of accuracy. On the other hand, nonoccupational exposure from manufacturing
and disposal sources has received much less attention. Exposure estimates
presented in this section are based on dispersion models using assumed emission
factors with questionable accuracy. In addition, little ambient monitoring
data is available to validate such models. Studies are further compounded
by nacuraJ background fiber concentrations.
14
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Asbestos Consumption Data
As discussed in Section 1, tl>e asbewtos consumption data used In this
report are those developed by the Bureau of Mines for 1980, Asbestos consump-
tion varies from year to year due to several factors, including the introduc-
tion of new products( the deletion of old ones, the increased use of asbestos
substitutes and natural fluctuations in business activity which affect the
production and delivery of all goods and services. In this report, asbestos
emissions estimates for each product category are related to asbestos con-
sumption data using emission factors developed by Suta and Levine.l To
understand the accuracy and validity of these emissions estimates, it is
therefore important to have a historical perspective on changes in asbestos
consumption. Such an overview will insure that the asbestos emissions esti-
mates developed will not underestimate or overestimate the extent of asbestos
release.
Table 5 presents biannual consumption data, by product category, for the
years 1976-1980. Two facts are evident from an examination of this table.
First, and most important in terras of emissions, is that overall use of asbestos
fibers decreased by 42 percent between 1978 and 1980. This decreased consump-
tion occurred in every product category and must primarily be attributed to a
general decline in business activity, especially in the automobile and building
construction sectors. Asbestos product categories such as friction products
and gaskets and packing, which reflect automobile-related asbestos use, and
those of asbestos-ceroent sheet and floor tile, which are associated with building
construction activities, declined significantly from 1978 to 1980. The net
Impact of this business slowdown is that the asbestos emission estimates
presented in this report, which are based on 1980 asbestos consumption data,
may not be representative of long term trends in asbestos consumption and emis-
sions. Nonetheless, the 1980 asbestos data is the most recent available and
will provide the basis for our emission estimates.
An examination of Table 5 also points out changes In asbestos consumption
for specific product categories and in so doing provides a commentary on the
quality of the data itself. With two notable exceptions, the- percent of total
asbestos consumption consumed by any product category remained relatively con-
stant from 1976 to 1980. The two exceptions are the paper products group,
which in this report includes paper, roofing products, thermal and electrical
insulation and flooring felt, and asbestos cement pipe. The paper products
category has lost a significant share of tot:'l asbestos consumption from 1976
to 1980, both in tons of asbestos consumed and percent of overall annual con-
sumption. A large part of this dramatic decrease, however, can be attributed
to an abnormally high consumption rate cited by the Bureau of Mines for roofing
products in 1976. Had this roofing consumption rate been closer to the previous
five-year average, 1976 paper asbestos use would have amounted to roughly 33
percent of total industry consumption and the decrease for this product category
from 1976 to 1980 would have been far less dramatic. The reason for the
abnormally high 1976 roofing products consumption figure has not been explained
by the Bureau of Mines. Users of this data must therefore recognize that while
it is the official government estimate for raw asbestos consumption, its
accuracy may be somewhat questionable.
15
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TABLE 5. BUREAU OF MINES ASBESTOS CONSUMPTION DATA, BY PRODUCT CATEGORY, 1976-1978-1980
1980
1976
1978
Product
category
Consumption
(metric tons)
Percent of
annual
consumption
Consumption
(metric tons)
Percent of
annual
consumption
Consumption
(metric tons)
Percent of
annual
consumpt ion
Paper®
328,000
50.0
154,100
24.9
90,020
25.1
Friction products
58,000
8.8
73,700
11.9
43,700
12.2
Asbestoa-cement
pipe
127,000
19.3
217,400
35.1
144,000
40.2
As be s tos-cement
sheet
21,000
3.2
36,100
5.8
7,900
2.2
Floor tile
41,000
6.3
50,400
8.1
36,080
10.1
Gaskets and packing
18,000
2.7
31,100
5.0
12,300
3.4
Sealants
18,000
2.7
19,100
3.1
10,900
3.0
Plastics
20,000
3.0
4,900
0.8
1,500
0.4
Textiles
7,000
1.1
2,900
0.5
1,900
0.5
Miscellaneous
19,000
2.9
29,700
4.8
10,400
2.9
TOTALS
656,000
100.0
619,400
100.0
358,700
100.0
aIncludes roofing, thermal and electrical insulation and flooring felt.
-------
The asbestos cetnent pipe category displayed an increasingly larger share
of the total asbestos consumption from 1976 to 1980. However, this percentage
increase is due more to the more rapid decrease in asbestos use by the other
product categories than it is to the increased use of asbestos in the manufac-
ture of asbestos concrete pipe. This is clearly shown by an examination <5f the
1978 and 1980 data. Between these two surveys, use of asbestos in pipe'produc-
tion decreased by roughly one third while the percentage of asbestos consumption
attributed to this category increased by five percent. These data strengthen
the argument that asbestos consumption data and the emissions estimates that
are derived from them must be clearly understood and not taken out of context
in order to accurately present the extent of asbestos release in the environ-
ment today.
Exposure Estimates of Suta and Levine
Suta and Levine* present detailed estimates on occupational and non-
occupational exposure to asbestos. Their study presents this data in terms of
the number of asbestos fibers inhaled per person per year. To do this, they
extrapolate asbestos concentration estimates to total annual asbestos inhala-
tion quantities using the following assumptions:
• The average person inhales 15 m^ of air/day
• For every optical-microscope visible fiber, there are 50 electron
microscope visible fibers
• There are 1000 electron-microscope visible fibers per nanogram of
asbestos
Occupational Exposure—
Based on Suta and Levine's assumptions, a maximum occupational exposure
level can be calculated. This level assumes that the worker is exposed tu the
maximum permissible workplace asbestos level of 2 optical-microscope visible
fibers per cc over a AO hour work-week. This 2 fiber per cc level can also
be expressed as an asbestos concentration of 100,000 ng/m-*. Using this maxi-
mum permissible concentration, a worker in the asbestos industry would inhale
125 billion electron microscope visible fibers or 125,000 ug of asbestos
annually. This estimate assumes that the average worker is employed for 50
weeks per year and inhales 5 m^ of air per day while in the asbestos laden
atmosphere. This estimate is roughly one-half that calculated by Suta and
Levine. While the rationale for their higher estimate is not clearly explained,
they apparently assumed a higher work-time inhalation rate. Typically,
asbestos workers are exposed to an average concentration of 1 f/cc and can
therefore be expei-ted to Inhale about 63 billion fibers per year. While the
occupational exposure discussion by Suta and Levine does not give an estimate
of the number of workers exposed, it does provide a rationale for calculating
occupational and nonoccupational exposure levels.
Nonoccupational Exposure—
Nonoccupational exposure to asbestos for persons living near asbestos
industrial facilltes was determined by Suta and Levine by applying assigned
17
-------
plant emissions to a mathematical dispersion model (Binorraal Continuous Plume
Dispersion Model developed by D. Bruce Turner). Suta and Levine based their
nonoccupational exposure estimates on emission estimates from the primary
asbestos industry only, excluding the secondary asbestos Industry and consumer
use related emissions sources. The determination of plant emissions was
based on 1974 production data and took into account improved air pollution
controls. The following assumptions were first made In order to calculate
nonoccupational asbestos exposure:
• A radius of 30 km is used to define a population living near
asbestos mines and mills as they are located in rural areas.
• A radius of 5 km is used to define a population near an asbes-
tos industrial facility which are generally located in urban
area.
• Plant emissions are those shown by Suta and Levine.1
Estimates of atmospheric concentrations and the annual amounts of asbestos
inhaled for persons living near asbestos industrial facilities are given in
Table 6. For this report, the roofing products segment along with 60 per-
cent of the flooring products segment were regrouped under paper products
to conform to CCA designations. Ambient background concentrations are included
in these estimates. Average atmospheric asbestos concentrations range from 21
to 33 ng/m^ for the various production categories in urban areas with the
annual amount of asbestos inhaled ranging from 115 million to 180 million
electron microscope visible fibers. As a point of reference, the median ambient
urban atmospheric asbestos fiber concentration as reported by Suta and Levine^
is 20 ng/m^ with 108.6 million electron-microscope visible fibers being
inhaled by the average person.* In contrast, the average asbestos worker can
be expected to inhale 63 billion electron-microscope visible fibers. Persona
living near mines and mills are shown by Suta and Levine* to be exposed to
much higher concentrations of asbestos than are persons living near asbestos
production facilities. Tailing piles are thought to be the major source of
emissions from mining and milling operations. As shown in Table 6, the average
asbestos concentrations near these operations is 400 ng/m^ with 2.2 billion
electron microscope visible fibers being inhaled by the average person resid-
ing near these operations. This still amounts to only about one-half of one
percent of the maximum allowable worker exposure and only about 94,000 persons
are affected since mines and mills are located in rural areas. It was, however,
reported in Lhis study' that the upper I percentile of the persons residing in
the vicinity of asbestos mines and mills might inhale occupational levels of
asbestos.
For rural areas it has been estimated that 10 percent of the population
which experiences maximum asbestos contact (upper tenth percentile) is exposed
to asbestos concentrations ranging from 8 to 100 ng/m^ for the various produc-
tion categories. In virban areas, the upper tenth percentile of the population
is exposed to concentrations ranging from 28 ng/m^ to 120 ng/m^. Persons
exposed to 120 ng/m^ are expected to inhale 660 million electron-raicroscope-
vlsible fibers/year.^ Both average and upper tenth percentile exposure levels
are presented in Table 6.
18
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TABLE 6. ATMOSPHERIC EXPOSURE TO ASBESTOS IN THE VICINITY OF ASBESTOS INDUSTRIAL FACILITIES1
Plants analyzed
Atmospheric asbestos Annual amount of
Estimated concentration3 asbestos inhaled®
portion of (ng/m-* or thousands fug or millions
Type of facility Number total plants (%) Background of fibers/m^)** of fibers)0
Mines and mills
5
100
Rural
400.0
(6000)d
2,190
(32,900)d
Friction products
51
90
Urban
23.0
(44)
125
(240)
Rural
3.4
(24)
19
(130)
Gaskets, packing,
39
65
Urban
24.0
(40)
130
(220)
or insulation
Rural
4.4
(20)
24
(110)
Textiles
24
95
Urban
21.0
(28)
115
(155)
Rural
1.3
(8)
7
(45)
Cement
35
50
Urban
27.0
(120)
148
(660)
Rural
7.2
(100)
39
(550)
Floor tile
9
90
Urban
21.0
(32)
115
(175)
Rural
1.0
(12)
5
(66)
Papere
58
80
Urban
33.0
(84)
180
(460)
Rural
13.0
(64)
71
(350)
aIncludes nominal atmospheric concentration background.
^Electron-uicroscope-visible fiber data were calculated from mass data assuming 1000 fibers/ng.
Actual conversion may be 100-10,000 fibers/ng; hence, reported figures may be one order of
magnitude high or low.
cConsumption assumes a daily inhalation of 15 m^.
^Median population exposure for indicated "at risk" population followed by upper 10 percent
population exposure in parentheses.
ePaper includes roofing products and 60 percent of flooring industry.
-------
Suta .md Leviuel determined process waste disposal Kites to be a major
source of atmospheric asbestos emissions with an estimated 383 metric tons
being emitted during 1974. Relying on several previous studies made prior to
1975, they determined the atmospheric concentration around disposal sites to
be on the order of 10 to 1000 times higher than typical background concen-
trations, possibly approaching occupational concentrations in some cases.
However, these estimates were based on emissions measurement made prior to
1975 sit which time stricter disposal regulations went into effect (40 CFR
62.15). But a and Levine estimated emissions from consumer waste in 1974 to
be 91 metric tons. Although much less than the emissions from process
waste disposal, consumer waste is more likely to be disposed in uncontrolled
waste dumps and be handled by persons unaware of the hazards.&
Ambient Monitoring Studies—
There is very little actual ambient monitoring data available to support
the human exposure estimates by Suta and Levine.1 Their ambient data was based
on estimates of plant emission rates which were subsequently used with atmos-
pheric dispersion modeling calculations. However, Bruckman and Rubino of the
Connecticut Department of Environmental Protection^ measured ambient asbestos
levels both adjacent to and removed from several different users of asbestos.
Approximately 40 monitoring sites were selected; ambient locations including
"typical" urban sites removed from known stationary sources of asbestos emis-
sions, r urn 1 -background sites, and stations contiguous to 4 industrial users
oi asbestos (i.e., manufarturers of Friction products, insulated wire and
cable, ammunition and molding compounds). Ambient chrysotile asbestos levels
removed from asbestos emission sources in both urban and rural locations were
below 10 ng/m3. However, asbestos concentrations near the industrial users
of asbestos exceeded Connecticut's proposed asbestos air quality standard of
'30 ng/m3, 30 day average. These measured levels Included 32 ng/m3 for a manu-
facturer of friction products; 33 ng/m3 for a manufacturer of insulated wire
and cable and a manufacturer of ammunition, located approximately 1/2 mile
apart; and 33 ng/m3 for a manufacturer of molding compounds. These elevated
levels occurred in spite of the fact that each source was in compliance with
NESHAPS and other current applicable state and federal air quality regulations.
Connecticut's actual atmospheric asbestos concentration measurement, in
the vicinity of Industrial facilities, closely resembles atmospheric concen-
tration estimates which Suta and Levine1 developed based on dispersion model-
ing (see Table 6). Suta and Levine estimated that average atmospheric con-
centrations, within 1.6 km of an industrial user, range from 28 to 120 ng/m3
for urban sources and 8 to 100 ng/m3 for rural sources. The range of fiber
concentrations presented is due to varying emission rates from different
industrial sources. Connecticut's measurements fall in Suta and Levine's
range, but it is important to note that Connecticut's samples, which exceeded
30 ng/m3, were measured within 1 km of the industrial user. Connecticut's
spot -ampl tng dat.i are too limited to estimate an average atmospheric concen-
tration over a given area, as provided by Suta and Levine. Nonetheless, the
actual atmospheric measurements obtained by Connecticut, support Suta and
Levine's atmospheric concentration estimates.
Atmospheric asbestos concentration estimates, based on dispersion model -
iiig, were also determined by GCA/Technology Division.^ The dispersion mod-
cling conducted by GCA differs from Suta and Levine in that actual emission
20
-------
rates were mciisurod , r.ilhrr than relying on gross i mission estiiiuiU-..
Snmples were taken lu tlu- exhaust vents ol nn asbestos paper plant to deter-
mine the averages asbestos concentration of the exhaust gases. The exhaust
gas fiber concentration data was combined with process aspiration rates to
determine total plant asbestos emission rates. Employing this datn in .1
Gaussian Plume dispersion model, it was estimated that plant-related asbestos
concentrations above 50 ng/m3 may be encountered within 500 meters of the
plant, depending on the meteorological conditions present. CCA/Technology
Division Dispersion Model estimates were made with actual emission measurement
data, and like the Connecticut data, support Suta and Levine's atmospheric
asbestos concentration estimates.
Emission Estimates
Suta and Levine made detailed estimates of air-borne asbestos emissions
resulting from the manufacture and disposal of asbestos containing materials.
These data have been upgraded to account for 1080 asbestos consumption figures,
and are presented in Table 7. As can be seen in this table, disposal emissions
from manufacturing are estimated to be 179 metric tons, compared to 86.8 metric
tons of process emissions. These estimates may be high as they fail to take
Into consideration new regulations regarding the disposal of asbestos-containing
waste (AO CFR 61.25). However, no current data exist on the degree to which
disposal sites are in compliance with the new disposal standard. In addition,
no measurements of emissions from disposal sites which are in compliance have
been made.
TABLE 7. AIRBORNE ASBESTOS EMISSIONS FROM PROCESS
AND DISPOSAL - PRIMARY INDUSTRY1
Industry segment
1980 annual
asbestos
consumption
(Mt/yr)
Asbestos emissions
to air/ Mt/yr
from from
Process Disposal
Total
Paper
90,0:>0
45.0
45.01
90.01
Friction material
43,700
10.86
21. 73
J2.59
A.C. pipe
144,000
14.24
71.92
86.16
A. C. sheet
7,900
0. 83
3.95
4.78
Floor tile
36,080
3.63
18.13
21.76
Gaskets and packing
12,300
6.12
6.12
12.24
Sealants
10,900
0.63
5.39
6.02
Plastics
1,500
a
0.74
0.74
Text lies
1 ,900
0.31
0. 92
1.23
Miscellaneous
10,400
5.22
5.22
10.44
TOT AT.
358,700
86.84
179.13
265.97
Minimal amounts
21
-------
After reviewing the Suta and Levine data, GCA has developed its own
estimates on asbestos releases from process and disposal operations. Visual
observations by GCA personnel at asbestos-containing waste disposal sites
have indicated that the majority of sites exhibit no visible emissions, and
therefore appear to be in compliance with Federal asbestos disposal regulations.
By assuming compliance to be at least 90 percent, GCA has estimated disposal
emissions to be reduced by at least ten times from Suta and Levine's estimate
of 17cj metric tons for uncontrolled disposal practices. This places disposal
emissions from manufacturing processes, updated to 1980 U.S. Bureau of Mines
consumption data, at approximately 18 metric tons. However, a tenfold reduction
may be a conservative estimate and a 100-fold reduction may more accurately
represent emissions using present day disposal techniques. GCA can therefore
state with reasonable confidence that emissions from disposal of manufacturing
wastes containing asbestos fall between 2 and 18 metric tons per year.
A summary of GCA's fiber release estimates is presented in Table 8.
This information is based on Suta and Levine's^- fiber release estimates for
process operations proportioned to reflect 1980 U.S. Bureau of Mines consump-
tion data for each industry segment. However, as stated above, GCA has esti-
mated emissions from disposal to be one order of magnitude lower than that
reported by Suta and Levine due to the recent regulations enacted to limit
emissions from disposal sites. Suta and Levine's emission estimates were used
as a basis tor estimating fiber release from process operations since it is
believed that their assumptions closely depict actual conditions.
TABLE 8. GCA ESTIMATES OF FIBER RELEASE FROM MANUFACTURING AND DISPOSAL - 1980
Annual asbestos Asbestos Emissions to air, Mt/yr
consumption
Mt/yr
From process
From disposal
Total
Paper
90,020
45.0
4.5
49.5
Friction
43,700
10.9
2.2
13.1
A.C. pipe
144,000
14.2
7.2
21.4
A.C. sheet
7,900
0.8
0.4
1.2
Floor tile
36,080
3.6
1.8
5.4
Gaskets and packing
12,300
6.1
0.6
6.7
Seal ants
10,900
0.6
0.5
1.1
Plastics
1 ,500
a
0.1
0.1
Textiles
1 ,900
0. 3
0.1
0.4
Mis cc1laneous
10,400
5.2
0.5
5.7
TOTAL
358,700
86.7
17.9
104.6
nimal amounts
22
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Atmospheric emissions from consumer disposal are estimated to be 28.5
metric tona by Suta .md Levine.1 Due to limitations in available data, this
study made no attempt to quantify human exposure from this source.
CONCLUSION
Baghouses are without question the most common type of air pollution
control devices used in asbestos milling and manufacturing. Baghouse collectors
have been determined to be highly efficient for removing long fibers although
there is a paucity of data concerning the collection efficiency for short
fibers. The use of wet scrubbers has greatly diminished, having been replaced
by baghouse collectors. Substituting baghouse filters for wet collectors has
the advantage of eliminating wastewater disrharges, in addition to providing
higher collection efficiencies. Cyclone collectors are primarily used only
as precleaning devices prior to a baghouse filter due to their poor perfor-
mance at removing small particles. However, cyclones are employed in ore
drying operations, where the combination of high temperature and humidity, in
addition to the relatively large particle size of the ore bound asbestos
fibers, makes cyclone collectors the most suitable type of control.
Recognition of Lhe dangers associated with asbestos exposure has lead to
regulations eliminating the past practice of open dumping of asbestos wastes.
Recent EPA regulations require disposai sites handling asbestos wastes to
take measures to eliminate visible emissions. In addition, asbestos-containing
wastes must be covered with at least 15 cm (b inches) of compacted nonasbestos-
containing material or be covered with a resinous or petroleum based-dust supres-
aion agent which effectively binds dust and controls erosion. Such currently
employed dust control techniques have significantly reduced the amount of
asbestos fibers released to the ambient air from a disposal site.
Emission estimates by Suta and Levine' place disposal emissions from manu-
facturing at a higher level than manufacturing process emissions. However,
as previously stated, recent EPA regulations have resulted in a significant
reduction In the amount of emissions generated at waste disposal sites. It
is estimated that disposal emissions have been reduced by one order of mag-
nitude relative to past practices.
CCA analyzed the assumptions made by Suta and Levine in estimating asbestos
emissions to the air from manufacturing and disposal. Suta and Levine1s esti-
mate for asbestos emissions from process operations totals 86.8 Mt/yr, when
their original 1974 estimates are upgraded to account for 1980 asbestos consump-
tion. GCA's process emission estimate is 86.7 Mt/yr and essentially agrees
with Suta and Levine's assumptions. GCA's estimate also takes into account
1980 asbestos consumption.
With regard to disposal emissions, GCA again used the SuLa and Levine
data as a starting point. However, GCA estimates that Suta and Levine have
not taken into account the widespread compliance of industry disposal sites
with applicable EPA regulations governing the ultimate deposition of asbestos-
bearing waste. Based on its belief that compliance with these regulations Is
from 90 to 99 percent complete, GCA has reduced Suta and Levine's estimates
23
-------
by 10 to 100 times, or to approximately 2 to 18 metric tons per year. The
later figure, 18 metric tons per yecir will be used in this report as GCA's
estimate lor disposal emissions from primary manufacturing.
There is a vast difference in population exposure estimates due primarily
to Insufficient data on process emissions and ambient asbestos concentrations.
However, recent monitoring studies and atmospheric dispersion modeling pro-
grams conducted by the Connecticut Department of Environmental Protection and
by GCA, show that elevated asbestos fiber levels are likely to be present in
the ambient air in the vicinity of asbestos manufacturing facilities. This
evidence supports the need for further monitoring of manufacturing emissions
and ambient levels of asbestos.
24
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REFERENCES
1. Suta, B. E., and R. S. Levine. Nonoccupational Asbestos Emissions and
Exposures. In: Asbestos, Volume I Properties, Applications, and Hazards.
L. Michaels and S. S. Chissick, eds., John Wiley & Sons, New York, NY,
1979, pp. 171-205.
2. Bruckman, L., and R. A. Rubino. Monitored Asbestos Concentrations in
Connecticut. J. Air Pollution Control Assoc. 28(12), pp. 1221-1226.
December 1978.
3. Control Techniques for Asbestos Air Pollutants. AP-117. U.S. Environ-
mental Protection Agency, Research Triangle Park, North Carolina,
February 1973.
4. Harwood, C. F., and T. P. Blaszak. Characterization and Control of
Asbestos Emissions from Open Sources. IIT Research Institute, U.S.
National Technical Information Service. PB-238-925. September 1974.
5. Jacko, M. G., and R. T. DuCharme. Brake Emission: Emission Measurements
from Brake and Clutch Linings from Selected Mobile Sources. U.S. National
Technical Information Service, PB-222-372. 1973.
6. Slttig, M. Pollution Control in the Asbestos, Cement, Glass, and Allied
Mineral Industries. Noyes Data Corporation, Park Ridge, New Jersey, 1975.
7. llarwood, C. F. , I). K. Ostreich, P. Siebert, and J. D. Stockham. Asbestos
Emissions from Baghouse Controlled Sources. American Industrial Hygiene
Association Journal, August 1975, pp. 515-603.
8. llarwood, C. F., P. Siebert, and T. P. Blaszak. Assessment of Particle
Control Technology for Enclosed Asbestos Sources. EPA-650/2-7A-098,
U.S. Environmental Protection Agency, Washington, D.C., October 1974.
9. Background Information on National Emission Standards for Hazardous Air
Pollutants. EPA-450/2-74-009, U.S Environmental Protection Agency,
Research Triangle Park, N.C., October 1974.
10. Manufacturing Waste Disposal and Utilization, In: Proceedings of the
Fifth Mineral Waste Utilization Symposium, Chicago, Illinois, April 13-14,
1976, pp. 308-318.
25
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11. Cogley, D. Modeling Atmospheric Asbestos Concentrations in the Vicinity
of an Asbestos Paper Plant. Unpublished. GCA/Technology Division,
Bedford, Massachusetts, September 1979.
12. Clifton, R. A. Asbestos, 1980 Bureau of Mines Mineral Yearbook, Washing-
ton, D.C. August 22, 1979.
13. Levine, R., ed. Asbestos: An Information Resource. May 1978.
26
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SECTION 3
MINING AND MILLING OF ASBESTOS
INTRODUCTION
Asbestos is a generic term encompassing a number of impure, naturally
occurring hydrated mineral silicates separable into filaments. Six commercial
varieties of asbestiform minerals have been identified and are presented
below according to the rock forming minerals group from which they originated.
Group
Variety
Formula
Amphibole
Anthophyllite
Mg7Si8022(0H)2
Araosite
(Fe2-fMg)7Si8022(0H)2
Crocidolite
Na2Fe^+(Fe2-*Mg) 3Si8022 (OH)
(blue asbestos)
Tremolite
Ca2Mg5Si8022(0H)2
Actinolite
Ca2(MgFe2+)5Si8022(OH)2
Serpentine
Chrysotile
(white asbestos)
Mg3[Si205](0H)4
Chrysotile, which accounts for 85 percent of the world's production and use,
is graded and grouped according to fiber length. The fibers are distinguished
by separation into eight groups numbered 1 through 8. Grade 8 is not used in
this country.^ j^e remaining seven grades and their product uses are dis-
cussed below:
• Grades 1, 2, and 3—Fiber lengths for these three grades are
greater than 19 mm, 10 to 19 mm, and 6 to 10 mm. respectively.
The major end-use products made from these fiber grades in-
clude textiles, clothing, theater curtains, different types
of packings, fireproof textile products, woven brake linings,
clutch facings, electrical insulation material, and high-
pressure and marine insulation.
• Grade 4—Grade 4 fibers range from 3 mm to 6 mm in length.
Their major use is in asbestos-cement pipe.
27
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• Grade 3—Grade 5 fiber lengths overlap with Grade 4, ranging
front 3 to 6 mm. Fibers within this grade are used in asbestos-
cement sheets, flat and corrugated sheets, low-pressure
asbestos-cement pipes and molded products. They are also used in
some paper products, such as pipe, insulation, wrappings and
other products including brake linings and gaskets.
• Grade 6—Fibers within this grouping are less than 3 mm long.
Primary use is in asbestos-cement products, gaskets, brake
linings, vinyl sheet backings and millboard.
• Grade 7—Grade 7 fibers are also less than 3 mm long. Fibers
within this group are used in molded brake linings and clutch
facings, asphalt compounds, joint and insulation cements, roof
coatings, plastics, and caulking compounds.
ASBESTOS MIMING
The fiber is mined and milled primarily outside the United States. Of
the estimated 1980 worldwide asbestos production (approximately 4.8 million
metric tons) only 80,000 m.t. or less than 2 percent was mined in the United
States.* Currently, four asbestos mining and milling operations are active
in this country: two in California and one each in Vermont and Arizona.
Details on American asbestos mines are presented in Table 9. According to
Table 9, 542 persons were employed in asbestos milling and mining in 1973.
More recent data indicate that current total employment in these operations
is approximately 480 persons.1
Three of the four active asbestos mines are open pits; underground
mining is practiced only in Arizona. In open pit mining, ore is removed from
shallow deposits with earth-moving equipment. Generally a shallow overburden
containing a low percentage of asbestos fiber must be removed to obtain access
to more concentrated asbestos veins below. Blasting may be required to reach
deeper fiber veins or to reduce boulders to a size acceptable to the mill.
Asbestos fibers can be emitted from overburden dumps and exposed ore; from
drilling and blasting; and from overburden and ore removal, loading and
transport.
Underground mines follow asbestos ore veins with shafts, galleries and
drifts using blasting and earth-moving equipment. Overburden removal is not
required and ore deposits are not exposed to weathering, thus reducing asbes-
tos fiber emissions. Significant amounts of dust may be generated during
transfer operations, but many of the dirtier processes occur underground.2
At the mines, coarse ore is typically crushed by a jaw or gyratory
crusher to an acceptable size. Oversize rock is separated by rotating
cylindrical trommel screens and is crushed in a secondary crusher. Ore is
conveyed to driers, or in larger installations! rotary kilns, where moisture
in the ore (up to 30 percent by weight) is removed. Dried ore is then placed
in storage, with large amounts being held to allow for any variation in fiber
demand and mine production which may occur over time. Prior to milling, the
dried ore may undergo an additional crushing step.
28
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TABLE 9. AMERICAN ASBESTOS
MINES AND MILLS
1,3
Operating company
Mine location
Employees3
Mill location
Employees3
Estimated production
(metric ton/yr)
Calaveras Asbestos Corp.
Calaveras County,
Calif.
36
Copperopolis,
Calif.
135
49,900b
Union Carbide Corp.
San Benito County,
Calif.
36
King City,
Calif.
50
25,000b
Vermont Asbestos Group
Hyde Park, Vt.
58
Hyde Park, Vt.
143
49,900b
Jacquays Mining Corp.
Gila County, Ariz.
8
Globe, Ariz.
5
2,700b
Total
159
383
1973 figures. A more up-to-date breakdown is unavailable. According to a U.S. Bureau of Mines estimate,
current total employment in United States mining and milling operations is 480 persons.1
K
"Annual figures based on daily production rate for 250 days/yr.
-------
At almost any step in the mining process, asbestos fibers can be released.
Weather clearly influences the extent of emissions. Rain and snow will cover
exoosed ore and overburden, while simultaneously cleaning the air and reducing
ambient asbestos levels. Mind has an opposite effect, distributing existing
emissions, entraining exposed fibers and reentraining settled fibers.
Blasting at the mine produces large quantities of dust which may contain
asbestos fibers. If rock, drilling at open pit mines is required to properly
place explosives, air-swept rotary and percussion drills are commonly used,
adding to dust emissions. Water-swept drills are more often utilized to re-
duce dust in underground mines, but are not used in large-scale field opera-
tions due to problems of water supply and the possibility of freeze up in
winter.
Al1 stages of ore handling (shoveling, screening, loading and unloading)
can generate emissions. Underground ore handling activities contribute to
ambient levels of asbestos as well as above ground activities since ventilation
air is generally exhausted to the atmosphere without any pollution control.
The most recent in-depth study of the types and effectiveness of pollution
control equipment used in asbestos mining operations was conducted by Harwood^
in 1973. At four major U.S. mines, dust control was found to be either limited
or else nonexistent. Cyclones were used In conjunction with drilling equipment,
in some cases, but emissions were still significant. Water sprays were used to
a limited extent to control dust during ore handling and blasting operations.
Ore was found to be transported from mines to mills in large open trucks,
covered only by loose-fitting tarpaulins, which could result in asbestos being
blown into the atmosphere. A high potential for fiber release was also found
to exist during the loading and unloading of ore. In addition, private road-
ways in the mine vicinity were paved with asbestos-containing tailings from
which fibers were released due to vehicular traffic.
Worker Exposure from Asbestos Mining
Recent data on the exposure to asbestos of persons employed in asbestos
mining operations are generally lacking. During 1971, employees at six active
asbestos mines were monitored to determine their time weighted average expo-
sure to asbestos fibers. Results are summarized in Table 10. A total of 140
samples were collected in the workers' breathing zones, with results ranging
from less than 0.1* fibers per cc to 7.8* fibers per cc as measured using the
NIOSH phase contrast (optical) procedure.5 The average mine worker exposure
was 1.2* fibers per cc. Drillers were exposed to the highest levels of
asbestos, with concentrations averaging 2.8* fibers per cc.
The asbestos mining and milling industry In the U.S. is regulated by
the Mine Safety and Health Administration (MSHA). Under MSHA standards, which
became effective in December of 1978, mine workers may be exposed to a maxim in
^Optical microscope visible fibers.
30
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TABLE 10. ASBESTOS FIBER EXPOSURES IN MINES (TIME-WEIGHTED AVERAGE)5
Asbestos fibers/m^ (>5 ym £n length)
Total
Occupation samples Highest exposure Lowest exposure Average exposure3
Driller
31
7.8
x
106
1.0 x 106
GO
•
X
106
Explosives man
6
0.6
X
106
0.1 x 106
0.3
X
106
Heavy equipment operator
55
1.7
X
106
0.5 x 106
1.1
X
106
Maintenance man
7
0.5
X
106
0.1 x 106
0.3
X
106
Truck driver
20
0.8
X
106
0.2 x 106
0.5
X
106
Other
21
O
CD
X
106
0.04 x 106
0.5
X
106
0
Arithmetic mean.
Note: Data are based on samples taken during 1971 at six mines with 118 employees.
All samples were collected in employee breathing zones, and analyzed by
optical phase contrast microscopy.
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of 2,000,000* f/m^ (2 f/cc) for an 8-hour work day. Under the same standard,
an exposure level of 10,000,000* f/m^ (10 f/cc) is allowed for periods of up
to 15 minutes per day. However, recent mine inspection data are lacking as
are data regarding the extent to which dust control equipment and practices
are being utilized.
Beat Available Pollution Control Technology
Spraying—
Water sprays have been used extensively in mining operations to control
dust emissions. Increased effectiveness has been achieved by mixing chemical
additives with the water. Salts, such as sodium, calcium and magnesium
chloride can be added to restrict the evaporation of water from the dust
while oils and polymers have been added to give a more permanent binding
action. Foam dust suppressing agents can be used in place of water sprays.
Foams cover more completely than water sprays and are therefore more
efficient.^
Drilling—
Air swept drills, designed to carry broken fragments and dust away from
the cutting face while reducing the temperature of the drill bit, are respon-
sible for high fiber levels. Emissions can be reduced on large rotary drills
by drilling through a platform. The platform itself serves as a hood while
rubber aprons attached to the platform with hinges provide a settling chamber
for dust raised during drilling. Mobile primary drilling units which have
attached compact bag filters currently offer the best method of dust control
for open-pit drilling. Air emissions can be reduced without the need for
filters by using water swept drills. The use of these drills is often limited
by the water supply and the potential for water pollution.
Blasting—
Blasting should be done in such a way that efficient rock removal is
achieved while reducing emissions at the same time. Emissions can be reduced
by using multiple detonations in place of one larger charge. Spraying water
around the blast site has been found to reduce emissions in this area but
does not control emissions from blast fragments. After changes have been
set, bags of water can be placed in the blast holes to reduce emissions due
to blast fragments.
Road Dust Control—
In Hay of 1974, federal regulations^ were adopted prohibiting the surfacing
of roads with asbestos-containing tailings. However, temporary roadways in the
areas of asbestos ore deposits are exempt. Emissions on roadways are generally
created by traffic. Dust can be blown from trucks transporting asbestos ore
while all vehicles can cause the release of asbestos from roads surfaced with
Optical microscope visible fibers.
^40 CFR Part 61 Subpart B - National Emission Standards for Hazardous Air
Pollutants.
32
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tailings due to the reentrainment of settled particles. In most cases,
spraying is the most practical method of dust control. Water can be used,
but must be reapplied often since it dries relatively fast. Better results
have been obtained using polymers and lignin sulfate or bitumen compounds.
Heavy oil controls dust successfully, but its use can cause problems with
odors and seepage. On paved roads vacuum sweepers may be preferable to
sprays since the dust is actually removed and emissions will not become a
problem once the road dries.
Ore Dumping, Crushing and Transporting—
Once mined the ore is dumped into a large "dumping pit" from which it is
fed into a jaw crusher to reduce particle size. The ore is then loaded on
trucks and hauled a short distance to an ore pile at a local mill. To control
emissions, the dumping pit can be enclosed and the crusher can be hooded and
exhausted to a baghouse. Loading and unloading can be carried out in venti-
lated, emission-controlled enclosures. A fine water spray can also be used
during loading and unloading to reduce emissions. Emissions during transport-
ing can be controlled by using closed bodied trucks or by using open trucks
with flexible impervious covers.^
ASBESTOS MILLING
Each asbestos mine has an associated mill where asbestos fibers are
separated from the ore, graded and packaged. Table 9, which lists active
asbestos mines in the United States, also lists active mills affiliated with
each mine.
Two milling techniques are used: air aspiration and wet separation. Air
aspiration involves frequent handling of the asbestos ore, fibers and tailings
creating numerous possible sources of emissions. The milling process Itself
takes place In hammermills, known as fiberizers, or in crushers which separate
asbestos fibers from the ore rock and from each other. Milled particles are
then shaken on progressively finer screens. Small rocks and fiber clumps pass
through the screens to the next level, larger rocks are conveyed to tailing
dumps or to crushing, and free fibers are removed from the sequence by airflow.
Separated fibers are conveyed to grading screens, classified according to
length, then sent to storage bins by grade. Different grades are blended to
obtain any desired final grade, which Is then bagged for shipment.
Exposure from Asbestos Milling
During 1971, employees at six asbestos mills were monitored to determine
their time-weighted average exposure to asbestos fibers. Results are summarized
in Table 11. A total of 436 samples were collected in workers' breathing zones,
with results ranging from a low of 1.2 fibers per cc to a high of 24.8 fibers
per cc measured using the NIOSH phase contrast (optical) procedure.5 The
average mill worker was exposed to 9.1 fibers per cc; it is assumed that,
stimulated by more stringent MSHA regulations, the average exposure has dropped
since 1971. For example, the laborer classification had the highest average
33
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TABLE 11. ASBESTOS FIBER EXPOSURE TN MILLS (TIME-WEIGHTED AVERAGE)5
Occupat ion
Total
Asbestos fibers/m3 (> 5 um in length)
samples Highest exposure Lowest exposure Average exposure
Blender, bagger and packer
132
24.8
X
10 e
2.7
X
106
11.3
X
106
Palletizer and car loader
31
18.1
X
106
1.2
X
106
10.0
X
106
Crusher and dryer operator
32
20.3
X
106
7.1
X
106
11.0
X
106
Foreman
32
15.8
X
106
4.3
X
106
8.3
X
106
Laboratory technician
33
17.4
X
106
4.5
X
106
8.8
X
106
Laborer
37
17.3
X
106
8.2
X
106
12.1
X
10 6
Maintenance man
50
16.9
X
10 6
3.8
X
106
8.4
X
10 6
Mill operator
50
17.9
X
106
4.7
X
106
11.5
X
106
Other
39
10.5
X
106
2.3
X
106
6.0
X
106
g
Arithmetic mean.
Note: Data are based on samples taken during 1971 at six mills with 370 employees.
All samples were collected in employee breathing zones, and analyzed by
optical phase contrast microscopy.
-------
exposure, 12,1 fibers per cc, due In part to sweeping, but vacuuming may have
superseded sweeping as the dangers of asbestos exposure have become known and
as regulations have tightened.
Best Available Pollution Control Technology
All processes described in the air aspiration milling method result in
fiber release. When first received from the mine, asbestos ore is stored
in large open ore stock piles. Windbreaks and sprays can be used to minimize
emissions from these piles. Since the air aspiration method of milling re-
quires that the ore be dry, wetting adds to the process cost. Before the
actual milling operations, ore is fed to an ore dryer where moisture is re-
moved by heating. Cyclones and multiple cyclones have been used extensively
to control emissions from this operation due to the relative insensitivlty
to high temperature and humidity of cyclones. However, the removal efficiency
is relatively low (about 70 percent)® and visible emissions are often generated.
Conventional baghouse filters cannot be used due to the high temperatures
generated by the process. Baghouses using orlon cloth bags are installed on
ore dryers in a Canadian mill operated by the Johns-Manville Corporation.?
The orlon material can withstand greater temperatures than can conventional
baghouse cloth while providing a much greater removal efficiency than cyclone
devices. In one mill in the U.S. the ore dryer is vented to a baghouse which
uses a heat resistant filter material trade named Nomex.^ Hammermills,
crushers, vibrating screens and automatic bagging machines can be hooded and
vented to a central baghouse filter. Central vacuuming systems can be used
to remove dust from the work areas. Ore is transported between different unit
operations by a belt conveyor. To control emissions, conveyors can be com-
pletely enclosed while transfer points can be hooded and vented to a baghouse.
Extensive conveyor systems are generally used to transfer mill tailings to an
onsite disposal pile. Numerous transfer points as well as the point at which
the tailings are dumped are potential sources of emissions. Emissions ran
best be controlled by wetting the tailings before they are placed on the con-
veyor and by using completely enclosed conveyor systems. After the tailings
have been dumped and graded, chemical stabilizers can be applied to limit
landfill emissions.
Since the wet separation method is a proprietary process used only in
one U.S. plant operating details are not available, but some factors influencing
emissions are known. Perhaps most important, because of the loosely bound
asbestos fibers in the ore at the source of this plant's asbestos, little or
no crushing is required. In addition, use of a wet separation technique re-
duces in-process asbestos emissions to the atmosphere while presenting a high
potential for water pollution.2
ENVIRONMENTAL REGULATIONS AND COMPLIANCE
In addition to MSHA's occupational exposure regulations, the U.S. Environ-
mental Protection Agency (EPA) has promulgated regulations* that require no
^National Emission Standards for Hazardous Air Pollutants (NESHAPs) 40 CFR
Part 61 Subpart B - National Emission Standard for Asbestos.
35
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visible emissions to be produced from milling or disposal operations, that
tailings be wetted before disposal, and that waste be covered with at least
15 cm (6 in.) of soil or with a resinous or petroleum-based dust suppressing
agent at least once in a 24-hour period. Inactive sites must be covered
with either at least 15 cm (6 in.) of soil and vegetation, or 61 centimeters
(2 ft) of soil, or be covered with a resinous or petroleum-based dust sup-
pressing agent. These regulations should greatly reduce the emissions from
waste piles which are believed to be the major source of airborne asbestos
emissions. However, recent data regarding compliance with the new regulations
is currently lacking.
In order to comply with the existing regulations most mills will have
had to have applied the best available technology. However, no current in-
formation exists regarding the extent to which emission controls are applied
or whether the mills are in compliance with the current regulations. The
most recent study of the control technology which is used in the mining and
milling of asbestos was presented by Harwood^ in 1974. In his study, Harwood
visited five mills, noting emission sources and types of control equipment
used. There was only one mill described in his report that could possibly
meet the present MSHA and EPA standards. In this mill the ore stockpile was
sprayed extensively. All of the milling operations, as well as ore drying
and bagging were enclosed and vented to a baghouse filter. Vacuum cleaning
was used extensively throughout the work area and dust was visible only in
the bagging room. Mill tailings were wetted before being conveyed to the
disposal site. In the other mills visited, Harwood found that baghouse filters
were used only with hammermills, crushers and screening devices while cyclones
were used to control emissions from ore dryers. Spraying of the ore pile and
vacuuming were practiced to a limited extent. Ore tailings were transported
dry to disposal sites using either enclosed or semienclosed conveyors. Gen-
erally no effort was made to control emissions at the disposal site. Visible
emissions from the ore drying and the tailing disposal operations were ob-
served. Dust was observed in almost all work areas and was particularly
heavy in the bagging room. The extent to which dust control practices and
equipment are applied in asbestos mills may have changed significantly since
Harwood's study. However, no recent inspection data is available and it is
not known to what extent the asbestos mills are in compliance with current
MSHA and EPA regulations.
ATMOSPHERIC EMISSIONS FROM MINING AND MILLING
Estimates of atmospheric emissions from the asbestos mining and milling
industry for 1974 are given in Table 12. The emission factors shown were es-
timated using recent emissions data and took into account the air pollution
controls used in 1974. The atmospheric emissions for each mill and mine were
calculated by multiplying the emission factor by the annual production. The
total emissions were estimated to be 373 metric tons from mining and 1039
metric tonB from milling. The combined emissions from mining and milling
were estimated to be 1,412 metric tons or 67 percent of all atmospheric asbes-
tos emissions generated in 1974. The majority of these emissions are thought
to have originated from wind erosion of tailing piles.®
36
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TABLE 12. ASBESTOS EMISSIONS TO AIR FROM MINING AND MILLING (1974)8
Emission factors Total atmospheric emissions
Annual (Kg/metric tons) (metric tons)
production
Mine (metric tons) Mining Milling Total Mining Hilling Total
Vermont 36,138 A 9 13 145 325 470
Coalinga3 27,104 4 18 22 108 488 596
Union Carbide 31,621 3 5 8 95 158 253
Copperopolis 4,517 4 9 13 18 41 59
Jacquay 2,710 2.5 10 12.5 7 27 54
Total 102,090 373 1039 1412
aAtlas Minerals Company has since closed its California Asbestos Mine and Mill.
-------
AMBIENT ASBESTOS FIBER CONCENTRATIONS
Background levels of asbestos vary according to location. Levels of 40
to 100 electron microscope visible fibers per cubic meter were found in a
remote area of California.^ Concentrations of asbestos in urban air have
been reported in one study to range from 0 to 2.400 electron microscope
visible fibers per cubic meter.®
A 1974 field survey of ambient asbestos levels in the vicinity of the
Atlas Asbestos Company mill in Coalinga, California, which is now closed,
showed 100 million electron microscope visible fibers per cubic meter within
500 meters of the mill tailings pile. Atmospheric concentrations of asbestos
100 meters downwind of an asbestos mill near King City, California were re-
ported to be on the order of 100 million fibers per cubic meter while, perhaps
due to unusual wind conditions. Concentrations on the order of 10 million
fibers per cubic meter were reported 500 meters upwind from the source. The
King City mill is unique in its use of a wet process; it is believed that
most of the fibers in the ambient sample originated in the mill's ore pile
and tailings dunp.^
NONOCCUPATIONAL ATMOSPHERIC EXPOSURE
in estimating nonoccupational exposure, Suta and Levine chose radii
of 5 km and 30 km to define a population living in an urban environment sur-
rounding asbestos-product manufacturing plants and rural settings around
asbestos mines and mills, respectively. Atmospheric asbestos concentration
for the rural areas surrounding asbestos mines and mills has been measured at
400,000 fibers* per cubic meter. The average value for urban settings is
25,600 fibers* per cubic meter or only 6 percent of the rural concentration.
By assuming that each person inhales 15 cubic meters of air per day, it can
be calculated that the average persons living near asbestos mines and mills
and those located near asbestos-product manufacturing plants will inhale
2,190 million fibers* and 140 million fibers* annually, respectively.
The rural concentration for mining and milling operations presented by
Suta and Levine^ are based on studies conducted prior to promulgation of the
1975 amendments to the Asbestos NESHAPs regulation. If the mines and mills
are in compliance then the current actual nonoccupational exposure may be
much less than that reported by Suta and Levine. Disposal problems could
presently exist due to the large amounts of tailings disposed and the large
area which the disposal site occupies (about 100 acres for a large mill).
Chemical dust suppression may be the desired method of erosion control due
to the cost and environmental problems associated with covering such a large
area with soil.*1 The tailings are aenerally highly alkaline, making vege-
tation as a final cover impractical.*1 Maintenance is relatively high on
inactive landfills where erosion is controlled by chemical dust-suppressing
agents, with reapplication necessary every I to 3 years.12
~Electron microscope visible fibers.
38
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REFERENCES
1. CLifton, R.A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of Mines,
Washington, O.C.
2. Sittig, M. Pollution Control in the Asbestos, Cement, Glass, and Allied
Mineral Industries, Noyes Data Corporation, Park Ridge, New Jersey,
1975.
3. Mcylan, W.M., P.H. Howard, S.S. Lande, A. Hanchett. Chemical Market
Input/Output Analysis of Selected Chemical Substances to Assess Sources
of Environmental Contamination: Task III. Asbestos EPA 560/6-78-005.
U.S. Environmental Protection Agency. Washington, D.C. August 1978.
4. Harwood, C.F. and T.P. Blaszak. Characterization and Control of Asbestos
Emissions From Open Sources, IIT Research Institute, U.S. National
Technical Information Service, PB-238-925, September 1974.
5. Schutz, L.A., W. Bang and G. Weeks. Airborne Asbestos Fiber Concen-
trations in Asbestos Mines and Mills in the United States, U.S. Bureau
of Mines Health and Safety Program, Technical Progress Report 72,
Denver, Colorado, June 1973.
6. Control Techniques for Asbestos Air Pollutants, AP-117, U.S. Environ-
mental Protection Agency, Research Triangle Park, North Carolina,
February 1973.
7. Coldfield, J. Fabric Filters in Asbestos Mining and Asbestos Manufactur-
ing, Paper 74-275, Presented at the 67th Annual APCA Meeting, Denver,
Colorado, June 9-13, 1974. P• 31.
8. Suta, B.E. , and R.J. Levine. Nonoccupational Asbestos Emissions and
Exposures, In: Asbestos, Volume 1 Properties, Applications, and Hazards,
L. Michaels and S. S. Chissick, eds., John Wiley & Sons, New York, N.Y.
1979, pp. 171-205.
9. Murchio, J.C., W.C. Cooper, and A. DeLeon. Asbestos Fibers in Ambient
Air of California. California Air Resources Board, March 1973.
10. Asbestos: An Information Resource, R.J. Levine, ed., DHEW Publication
Number (NIH) 79-1681, National Cancer Institute, U.S. Department of
Health, Education and Welfare, Public Health Service, National Insti-
tutes of Health, Bethesda, Maryland, May 1978, p. 105.
39
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Background Information on National Emission Standards for Hazardous Air
Pollutants, EPA 450/2-74-009, U.S. Environmental Protection Agency,
Research Triangle Park, N.C. October 1974.
Ase, P., J. Huff, F„. Huff, C.F. Harwood, and D. Destreich. Asbestos
Manufacturing Waste Disposal and Utilization, In: Proceedings of the
Fifth Mineral Waste Utilization Syoposiiaa, Chicago, Illinois, April 13-14,
1976, pp. 308-318.
40
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SECTION 4
ASBESTOS PAPER PRODUCTS
INTRODUCTION
Asbestos paper products are defined in this report to include any product
manufactured on a fourdrinier or cylinder papermaking machine. This defini-
tion serves to group together products with similar asbestos handling, produc-
tion and emission control equipment. Such a grouping minimizes the number of
product categories and avoids repetition. Asbestos paper products include
nine general categories. Listed in their order of descending annual consump-
tion level they are:
• Flooring felt
• Roofing felt
• Beater-add gaskets
• Pipeline wrap
• Millboard and rollboard
• Specialty papers
• Commercial papers
• Electrical insulation
• Beverage and pharmaceutical filters
The U.S. Bureau of Mines estimated the 1980 consumption of asbestos fiber in
these paper products to be 90,020* metric tons or 25 percent of all asbestos
consumed in the United States.^ Table 13 shows the approximate percentage
use of asbestos fiber in asbestos paper products by subcategories.
*This figure was arrived at by rearrangement of Bureau of Mines Data such
that paper products could now include roofing and flooring felt figures,
which were extrapolated from roofing and flooring product categories
respectively.
41
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TABLE 13. ESTIMATED USE OF ASBESTOS FIBER IN
PAPER PRODUCTS2 - 1979
Percent of
Category consumption
Flooring felt 45
Roofing felt 33
Beater-add gaskets 9
Pipeline wrap 5.6
Millboard 3.0
Electrical insulation 0.4
Commercial paper
General insulation 1.3
Muffler paper NA
Corrugated paper NA
Specialty papers
Cooling tower fill 0.9
Transmission paper 0.4
Chlorine electrolytic diaphragms 1.1
Decorative laminates NA
Beverage and pharmaceutical filters 0.03
NA * Not available but considered small.
PRODUCT DESCRIPTIONS
Flooring Felt
Composition—
Asbestos flooring felts are composed of about 85 percent asbestos and 15
percent latex binder.*¦ The latex binder is normally a styrene-butadiene type,
although acrylic latexes have been used in the past.2 Chrysotile asbestos is
used with the shorter fibers, grades 5 through 7 predominating. These grades
are normally obtained from Canada although limited quantities are available
domestically. The domestic grades are mostly used, however, to make vinyl-
asbestos floor tiles in which the asbestos fibers are used as a reinforcing
agent for the vinyl and not as a backing (see Floor Tile section).
Uses and Applications—
Most asbestos flooring felt is sold commercially and is used in residen-
tial applications. Due to its special qualities, asbestos felt backing is used
with vinyl sheet flooring as a general floor surfacing medium. Asbestos back-
ing is particularly useful in prolonging floor life when moisture from below
the surface is a problem.
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Special Qualities—
Asbestos is used in flooring felts to add dimensional stability and other
Important properties necessary in flooring such as high moisture, rot, and
heat resistance. These qualities have allowed asbestos to successfully coo-
pete with previously successful flooring felt materials—organic and jute
felt—such that asbestos has now largely replaced them as a backing material.
Roofing Felt
Composition—
Asbestos roofing felts are composed principally of asbestos fibers (85 to
87 percent).^ Other materials, such as wet and dry strength polymers, kraft
fibers, fiberglass, and mineral wool, are also often used as filters. Sheets
are saturated with coal tar or asphalt. The paper is made in either single
or multilayered grades and may have fiberglass filaments or wire strands em-
bedded between paper layers for reinforcement. Usually grade 6 or 7 chryso-
tile fiber imported from Canada is used in roofing felt.
Uses and Applications—
Asbestos roofing felt is primarily used for built-up roofing and as an
under layer for other roofing products. Built-up roofing is attached to the
roof deck by adhesive tars or by nailing if the roof deck can accept nails.
There are three basic types of built-up roofing; gravel surface, smooth-surface,
and mineral surface.3 As an underlayer for other roofing products, asbestos
roofing paper is attached to the roof deck, again by tar adhesives or by
nailing. It is then covered by shingles, cement sheets or other forms of
common roofing.
Special Qualities—
Asbestos is used in roofing felts because of its dimensional stability
and resistance to rot, fire, and heat. Rot resistance is particularly impor-
tant due to roofing felt's use on flat or nearly flat roofing with poor
drainage. Given the rapid heating and cooling of roof surfaces, felt crack-
ing is a prime concern, particularly in damper climates or in areas where snow,
subject to periodic melting, has accumulated on the rooftop. Asbestos felt
resists cracking, perhaps better than any competing product.
Beater-add Gaskets
Beater-add gaskets are so named because of the process used in their manu-
facture: Asbestos fibers and binders are added in the beaters of the paper-
making process. Other types of asbestos gaskets, such as compressed sheet
gaskets, are not paper products and are discussed elsewhere.
Composition—
Beater-add gasket papers are composed of 60 to 80 percent asbestos fibers
and 20 to 40 percent binders, usually latex.2 The latex polymer used deter-
mines the material's suitability for use in water, aqueous solutions, oils,
fuels, or chemical environments. Polymers used as binders in addition to latex
include natural rubber, various synthetic rubbers, neoprene, nitrile, and other
elastomers.
A3
-------
Nearly all domestic beater-add gaskets are formulated with various grades
of chrysotile asbestos although in the past, small amounts of crocldollte
asbestos were used on customer request since crocidolite is preferable to
chrysotile in applications involving strong mineral acids and alkalis. At
present a no domestic manufacturers report using crocldollte asbestos In gasket
paper.
Uses and Applications—
Gaskets are installed to obtain tight, nonleaking connections in piping
and other joints. Asbestos gaskets are used mainly by the automotive industry
in a variety of applications, including heat gaskets, carburetor gaskets,
manifold gaskets, and oil and transmission gaskets. In addition, asbestos
gaskets are widely used in other transportation applications, such aa trains,
airplanes, and ships. Further, they are used In industrial and commercial
equipment of all varieties, including heat exchangers, boilers, furnaces
and pipe connections. The chemical industry uses asbestos gaskets extensively
for piping, reactor and equipment connections because of the high chemical
Inertness of asbestos.
Special Qualities—
Asbestos is used in beater-add gaskets because it is not only heat resis-
tant , resilient, and strong, but is also chemically inert which is Important
for many chemical applications. No other material currently available
possesses all of these characteristics for beater-add gasket applications.
Pipeline Wrap
Composition—
Asbestos pipe wrapping papers contain a minimum of 85 percent asbestos,
are commonly reinforced with parallel strands of fiberglass for strength, and
are saturated with either coal tar or asphalt.2 They also may contain
cellulose and starch binders.
Uses and Applications—
Asbestos pipe wrap protects underground pipelines from corrosion. The
wrapping paper is normally attached to the outside circumference of the pipe
by machine winding. On occasion, it is attached via hand winding during spe-
cial field fabrication or damage repairs. The wrap can be attached or bonded
to the pipe surface by special adhesive coatings or by hot enamels that are
coated onto one side of the paper. The coatings or enamels also aid in the
corrosion protection of the pipe.
Special Qualities—
Asbestos paper has been successful as pipeline wrap due to the ability
of asbestos to resist soil chemicals, rotting, and decay, while maintaining
dimensional stability throughout its lifetime. These qualities are very Impor-
tant for underground pipeline wrap, as well as for the few times that asbestos
pipe wrap may be applied above ground.
44
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Millboard and Rollboard
Composition—
Asbestos millboard is composed primarily of asbestos fibers; asbestos
content ranges from 68 to 95 percent by weight, with 70 percent considered
typical.^ Group 5 chrysotile fibers are preferred. Binders, which may
be starches, elastomers or silicates or, less frequently, glue, cement and
gypsum, usually account for 3 to 25 percent by weight. Mineral wool, fiber-
glass, and cellulose are commonly used as filler.
Insulating board is a specific subcategory of millboard consisting of
asbestos with a calcium silicate (lime/silica) binder. In this product, amo-
site is used instead of chrysotile because it provides a higher degree of
reinforcement at low board densities and has favorable drainage properties.
Uses and Applications—
Asbestos millboard is rot-resistant, will stand up to many corrosive gases
and liquids, and is fire and temperature resistant. This makes millboard parti-
cularly important as a lining in floors, partitions, ceilings and fire doors,
and as an insulating barrier in stoves, ovens, and heated appliances. It has
important uses in metal and chemical industries as well. Table 14 illustrates
industry applications.
TABLE 14. INDUSTRIES USING ASBESTOS MILLBOARD AND
INDIVIDUAL APPLICATIONS5
Industry Application
Electrical
Appliance
Aluminum
Marine, shipyard,
aircraft
Foundry
Steel
Metallurgical
Ceramic
Glass
Thermal protection in large circuit breakers
Fireprooflng agent for commercial and home
security boxes, safes, and files
Pouring trough cover and trough liner
Liner for container that catches hot metal
from cutting operations
Trough liner and iron trough cover
Backup insulation for furnace lining
Used between the hot mandrel and the bearing
shell in molten babbit operation
Low mass kiln cars
As insulation in glass tank crowns, melter,
refiner, sidewalls, etc.
45
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Special Quailties—
Millboard varieties differ in their ability to withstand elevated tem-
peratures: standard millboard is good to 427°C and high quality millboard
is rated to 538°C. Above S66°C even high quality millboard becomes brittle.
Rollboard differs from millboard in that it is thin enough to
permit flexibility. Consequently! rollboard cannot survive elevated tem-
peratures. Rollboard is also relatively thin which contributes to its low
upper temperature limit, 1776C.
Electrical Insulation
Composition—
The composition of asbestos electrical insulation paper varies with the
intended application but generally contains chrysotile asbestos fibers and
cellulose bound with latex polymers. Small amounts of amosite and tremolite
are also used occasionally.
Electrical insulation is frequently impregnated with solid resins to
increase dielectric strength, improve mechanical properties and provide
moisture-proofing characteristics offsetting the hygroscopic property of
asbestos fiber. Depending upon the expected temperature of service, resin-
bonded papers or boards may use phenol, formaldehyde, polyvinyl acetal, epoxy,
or silicone resins. Glass or other fibers may also be present.^
Uses and Applications—
Asbestos is used in the electrical industry in the form of paper, tape,
cloth and board. It may be applied as a felted material or as a filler for
natural and synthetic insulating resins. The largest use of asbestos elec-
trical paper is as insulation for dry transformers, for layer insulation,
layer barriers, core barrier tubes, general conductor wraps, lead insulation,
and cross-over insulation.
Appliances that use asbestos papers for wire insulation include stoves
and toasters. The extent to which asbestos paper is currently used for these
applications is not clear, but use has dropped significantly due to manu-
facturer concern and the increased availability of substitutes.
Special Qualities—
Asbestos is used in electrical paper insulation because of its high
thermal and electrical resistance, which permits the paper to act effectively
as an insulator and protects the conductor from fire.9
Commercial Paper
Composition—
The commercial asbestos paper category encompasses a broad range of papers
that differ primarily in weight and thickness. The product is normally com-
posed of 95 to 98 weight percent asbestos fiber and 2 to 5 weight percent
starch binder.^ Short and medium grades of chrysotile are used.
46
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Muffler paper contains a very high percentage of asbestos fiber and
only a small percentage of starch binder. The surface of the product is
waffled or indented.
Corrugated asbestos paper is a commercial paper product corrugated and
cemented to a flat paper backing, sometimes laminated with aluminum foil.
Corrugated paper is manufactured with a high chryotile asbestos content and
a starch binder.
Uses and Applications—
General asbestos insulation papers are used in steel and aluminum fac-
tories for thermal insulation in annealing furnaces, trough lining for
smelting process, and refractory lining.
Muffler paper is used by the automotive industry primarily in the con-
struction of catalytic converters for exhaust emissions control systems.
The paper is applied as a wrap between the inner and outer skins of the con-
verter or muffler.
Corrugated asbestos paper is used as a thermal insulator for pipe covering,
block insulation, and specialty panelings. Applications of corrugated asbes-
tos paper include appliance insulation up to 150°C, hot-water and low-pressure
steam pipe insulation, process line insulation, and panel insulation, such as
paneling in elevators.
It should be noted that a large portion of the commercial paper produced
is sold to distributors and/or converters who, in turn, sell to their customers.
Thus, due to the large number of people involved in the production and con-
version process, it is nearly impossible to identify all of the specific end
uses which might arise in the production and conversion process.
Special Qualities—
Asbestos is used in commercial papers because of its resistance to fire
and corrosion. It provides commercial papers with the strength and durability
needed for numerous applications.
Specialty Papers
There are six major classes of asbestos specialty papers:
•
Cooling tower fill
•
Transmission papers
•
Beverage and pharmaceutical filters
•
Electrolytic diaphragms
•
Decorative laminates
•
Metal linings
47
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Composition—
The base for cooling tower fill consists of a blend of two grades of
chrysotile asbestos bound with DuPont neoprene latex; the content is 90 to
91 percent asbestos and 9 to 10 percent binder.^ Asbestos transmission
paper is a latex-bound product currently made with chrysotile asbestos.
Electrolytic diaphragms are made from mixing asbestos fibers and water to
form a slurry. Decorative laminates are produced by impregnating asbestos
electrical paper with thermosetting resins and then fusing multiple layers
together at high temperature and pressure. They are asbestos paper that is
formed in thin, rigid sheets and then colored or patterned accordingly. They
contain asbestos and a phenolic or melamine resin. Industrial laminates
consist basically of asbestos fibers, combined to make electric paper with
thermosetting resins added.
Metal lining paper is manufactured like commercial asbestos paper except
that the metal lining paper contains a higher percentage of binder and a small
percentage of clay.
Uses and Applications—
The major use of asbestos fill in cooling towers Is in applications where
high heat resistance is necessary. One such application is in gaseous diffu-
sion as performed at the governmental facilities in Oak Ridge. The Munters
Corporation produces a fill, "Asbedek," used mainly in mechanical draft towers.
Automobiles equipped with automatic transmissions get their drive from
metal transmission disks covered with a super-tough asbestos paper.Four-,
six-, and eight-cylinder autos with power shift contain from 8 to 12 of these
paper-lined disks.
Asbestos beverage filter paper is used by beer, wine and liquor distilling
industries to remove microorganisms and fine solids from the liquid mediun.
Pharmaceutical and cosmetic industries use the paper as well.
Asbestos is used as a diaphragm in production of chlorine via brine elec-
trolysis. Asbestos paper sheets were used in diaphragm cells through the
1930s and 1940s but now almost all diaphragm cells made with asbestos use a
slurry12 of water mixed with asbestos, rather than as a paper. The slurry is
vacuun-deposited onto a cathode pole, and the diaphragm is built-up inside
the electrolysis cell.
Decorative laminates can be bonded to plywood, fiberboard, or metals and
can be sawed, drilled, or sanded with conventional woodworking equipment.
Decorative laminates appear generally in wall or ceiling paneling, desk tops,
counter tops, and worktable tops. Asbestos is only one of many materials
from which decorative laminates can be made; the bulk of decorative laminates
are made with kraft papers. Industrial laminates are used for telephone
switchboard construction, television circuit boards, and other electronic
applications. Tube and rod laminate can also be used as core or winding
barriers for such equipment. The sheets can also be stamped or fabricated
into specialty spacers or washers.
48
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Metal lining paper Is used as a corrosion-res1stant liner for both metal
sidings and culvert pipe. Culvert pipe Is in turn used for landfill drainage
and water treatment applications.
Special Qualities—
Asbestos is used in specialty papers primarily due to its chemical and
heat resistant properties.
Asbestos is used in cooling tower fill for its heat and chemical resis-
tance. In applications where high heat resistance is necessary, asbestos
paper will continue to be used, because of its proven durability and heat
resistant qualities. Extensive government testing at governmental facilities
at Oak Ridge*-* found asbestos fill (Asbesdek) superior in performance to
alternatives.
Asbestos is used in transmission papers for its excellent friction charac
teristics and oil resistance as, during use, the paper-lined disks are nor-
mally coated with transmission oil. Asbestos has been found to be durable in
this application.
For beverage and pharmaceutical filters, asbestos represents a mineral
medium that does not degrade or otherwise affect liquid quality while acting
as a suitable filter. In the electrolytic diaphragm, it provides strength
and the appropriate properties needed for manufacturing this product. In the
electrolytic process, cathode surfaces are generally lined with a layer of
asbestos either in the form of paper or as vacuum-deposited fibers.^ The
asbestos maintains the caustic strength and minimizes the diffusionsI migra-
tion of hydroxyl ions. All diaphragms gradually clog with residual impuri-
tioes in the brine and particles of graphite from the anode, and therefore
must be renewed at regular intervals (approximately every 100 days).^
High-pressure industrial laminates are a significantly more durable form
of the decorative product. Asbestos is no longer being used in any signifi-
cant quantity in making decorative laminates.*® Asbestos paper was used to
produce a special fire-retardant decorative laminate; fire retardant laminates
are used for interior surfacing and paneling public buildings, buses, rail-
cars, and ships requiring a Class 1 fire-resistant rating.*' Decorative
laminates are thin, rigid sheet materials that have been resin-saturated to
press the layers together. They are faced with decorative colors or patterns
and characterized by showing resistance to damage from scuffing or scratching.
Industrial laminates are sheets produced from asbestos electrical paper fused
at high temperatures. Asbestos electrical paper is used here to allow for
effective insulation and to protect the conductor from fire.
Asbestos is used in metal lining paper to provide corrosion-resLstance
and strength.
49
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Beverage and Pharmaceutical Filters
Composition—
The major difference between asbestos beverage filters and other asbestos
paper products is the formula.
Asbestos beverage filters may contain, In addition to asbestos, cellulose
fibers, various types of latex resins and, occasionally, diatomaceous earth.
The asbestos content varies from a high of 50 percent for pharmaceutical
filters to aa low as 5 percent for rough filtering applications. In general,
the higher the asbestos content, the better the filtering qualities. The grade
of asbestos used is a very high-purity grade (longer fiber; thus in the lower
grade numbers) obtained, when, available, from Arizona mines; a usable grade
is also available from Canada. This particular high-purity grade of crystotile
must be free of trace minerals such as iron and calcium.
Uses and Applications—
Asbestos filter sheets are primarily used by the beer, wine, and liquor
distilling industries to filter (remove) microorganisms, fine, or very fine
solids from liquids. In the beverage industry, there are several filtration
steps; asbestos filter papers have most commonly been applied for "sterile"
filtration, the complete removal of all yeast cells and microorganisms, both
aerobic and anaerobic, that might have survived previous filtration.18 As-
bestos filters are also used for haze clarification, removing cloudiness from
the liquid product and giving it a sparkling clarity.
At present, about 30 percent of the wine industry, 10 percent of the
beer industry, and 25 percent of the distilling industry use some form of
asbestos filtration.*9 Asbestos filter paper is also used for specialty
applications in the cosmetics and pharmaceuticals industries and for the fil-
tration of various fruit juices, such as apple juice.
Special Qualities—
Asbestos is used In filters because it has an exceptionally large surface
area per unit of weight and a very unusual natural positive electrical charge.
This positive charge is very desirable for removing particles from beverages
as the particles are usually negatively charged. Although other substances
may be used aa filter materials, asbestos appears to provide one property
required by some beverage manufacturers which its competitors lack—that of
the removal of haze from liquid beverages. The filtering efficiency of non-
asbestos sheets is considered about equal to that of asbestos, aside from haze
removal capabilities. Substitutes for asbestos filters are readily available
and will likely undergo further Improvements as they are developed. As far as
is known, substitutes seem to equal asbestos in durability and service life.
SUBSTITUTES
Asbestos is used in paper products for the variety of qualities it im-
parts to the product. Qualities such as dimensional stability, resilience,
thermal and electrical resistance, strength, and overall resistance to mois-
ture, fire, decay, rot and chemicals make asbestos a unique yet vital raw
50
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ingredient to the paper product categories previously described. Individual
paper products use some or all of these qualities and the ability of a sub-
stitute to replace asbestos depends on the degree to which it can replace
one or more of these specific qualities. Substitutes may occur in two forms:
as a fiber substitute in which the asbestos fiber is replaced in the manufac-
ture of the paper product* or as a completely different asbestos-free material
which attempts to duplicate some or all of the characteristics of the original
asbestos product. The commercial availability of either or both substitute
forms for each paper product category will be subsequently discussed.
Potential fiber substitutes in asbestos flooring felt that have been
, studied include fiberglass, cellulose, Nomex, and other polymeric fibers.
However, at present none of these have been found to be an acceptable sub-
stitute for asbestos. Material substitutes however are available which
replace the need for asbestos felt backing in vinyl floors, either by pro-
viding a complete covering in and of itself as in carpeting, wood floors and
"place and press" vinyl tile squares, or by providing another type of backing
as in foam-cushioned backings, and even backless sheet vinyl. The choice
between carpeting, wood floors and vinyl tile squares is usually made by cus-
tomer preference. Foam cushioned backings are formed by attaching a cellulose
foam layer to sheet vinyl surfacing. "Backless" sheet vinyl is actually a
sheet flooring with a special vinyl backing which allows the floor to stretch
and contract. Both of these products are actively competing with asbestos
backing today. In addition, a flooring system "sandwich" consisting of a
vinyl surface, a foam cushion midsection, and an elastic vinyl backing is
also being produced, and it is expected to provide increased competition for
asbestos flooring felt in the future.
Alternates to asbestos roofing felt include organic felt, fiberglass
felt and a rubberized single-ply membrane roofing system. Organic felts and
fiberglass felts, like asbestos roofing felts, are saturated with coal tar
or asphalt before use. Organic felts, though the least durable are the most
widely used as they are the lowest in cost. Fiberglass is stronger, more
durable, longer wearing and more heat resistant than organic felt, but accord-
ing to some, because the material is so new, conversion will require both
manufacturing experience and applicator training. 0 Single-ply membrane
roofing is applied to the roof deck cold, an important attribute when city
ordinances or other considerations prohibit hot tar. Single-ply membrane
systems are roughly 5 to 10 percent more expensive than asbestos, however
they are relatively new and their durability is yet to be proven. Finally,
Johns-Manville produces the GlasPly built-up roofing system which utilizes
asphalt-impregnated fiberglass ply felts. This system requires less mopping
asphalt than other systems because more asphalt is impregnated during
manufacturing.21
Three basic alternatives to asbestos beater-add gaskets exist: ceramic
paper, Teflon, and all-metal products. Silicone rubber is also a potential
substitute, as it is serviceable to 316°C; however, its applications are
limited because it cannot be used in the presence of certain oils and fluids.
Ceramic paper has the heat resistance of asbestos, but is not particularly
resilient and is deteriorated by oil,^ effectively eliminating it from pos-
sible use in automobile gaskets. Ceramic paper does have good resistance
51
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to some chemicals and in some high temperature applications has been shown to
outlast asbestos. For example, ceramics have been used in place of crocido-
lite asbestos paper as a layering paper in sulfuric acid production.^2 Fiber-
frax paper, composed of ceramic fibers, inert fillers, and organic bonding
agents can be used as a direct substitute for some asbestos gaskets.^3
Teflon is not a resilient, rubbery material as is asbestos; rather it is
plastic, tending to deform and flow under loads. Due to its nonsticking pro-
perties, Teflon is difficult to retain in joints so it is commonly used with
an asbestos paper filler.
As with Teflon, all-metal gaskets are not resilient but are useable in
limited applications. Because of the lack of resilience, all-metal gaskets
cannot be substituted directly in most automotive applications.
Saturated fiberglass is becoming more and more competitive with asbestos
in pipe protection because it has many of the characteristic advantages of
asbestos. A comparison of the pipeline protection of fiberglass versus asbestos
is very similar to the discussion of fiberglass roofing felt versus asbestos
roofing felt. Fiberglass is more dimensionally stable, rot resistant, and
stronger than organic materials, yet asbestos still enjoys slight advantages
in these qualities. Asbestos also has a better fire rating than fiberglass.
Fiberglass has the advantage of requiring less asphalt saturation than asbes-
tos and, given the escalating cost of petroleum products, this may mean a
lower cost.
In addition to fiber replacement in pipeline wrap, there are a variety
of asbestos-free coating materials which are potential substitutes. These
Include enamels, extruded plastics (polythylene and polypropylene), fusion
bonded thermosetting powder resins, liquid epoxy and phenolics, tapes, wax
coatings, polyurethane foam insulations and concrete.
Several of these materials have been available for years while others have
been introduced fairly recently. Although wax coatings, polyurethane foam
insulations and concrete may be used in only special situations, other coat-
ings, such as extruded plastics, provide excellent moisture, rot, and chemical
resistance as well as strength and therefore can be used in most general
applications.
Plastic tapes, although not adapted for use as pipeline wrap to date,
display excellent moisture resistance. However, some can be attacked by
various soil chemicals (depending upon application). Research in this area
may be applicable in the future if the use of plastic in pipe wraps looks
viable as an alternative, as plastic has been used in this area in the past.
The principal substitutes for asbestos millboard and rollboard are
fiberglass, mineral wool, and alumina silicate (ceramic) boards, although
vermiculite compositions have also been successfully employed. These product
substitutes are manufactured by several companies, Including Carborundum,
Johns-Manville, Babcock and Wilcox, and Pars Manufacturing Company. These
52
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substitutes generally have equal or superior Insulating qualities relative
to asbestos but most have significantly higher prices.
Substitute products currently available for electrical and thermal in-
sulation Include DuPont's Nomex Paper, Carborundun Corporation's Ceramic
Fiberfrax^Paper, Manning Paper's Manninglass, and Masonite's Benelex 402.
Nomex is an aramld paper composed mostly (85 percent) of a highly aromatic
polyamide synthetic material.2'' Polyamides as well as polyethersulphone
are high temperature polymeric materials which have insulating qualities
similar to asbestos. Fiber£rax® is a homogeneous product composed primarily
of silica and alumina held together with an organic binder.25 it ia a paper
that exhibits good dielectric strength, is somewhat stiff and can be cut and
handled easily. Manninglass is a glass fabric. Like most glass fabrics,
when wrapped tightly onto wire and treated with resins, it is more vulnerable
to abrasion than most other wire coverings and is not suited for applications
requiring severe flexing. Benelex 402 is a dense lignin-resin cellulose
laminate. It is able to withstand abrasive action, acidic conditions and
steam cleaning.26
Substitutes which may be used in place of asbestos commercial paper in-
clude ceramic, cellulose and fiberglass products. Applications vary, and
those products demonstrating high temperature resistance appear to lack the
ability to couple this with sustained strength. Ceramic paper can be used
at higher temperatures than asbestos; however it has not been proven to be
as strong or as resilient as asbestos paper. Cellulose and fiberglass papers
generally lack the heat resistance and dimensional stability required for
heat and flame resistance.
Substitutes for specialty papers include:
Specialty paper
cooling tower fill
polyvinyl and polypropylene plastics
cellulose
aluminum
steel
Substitute product
transmission paper
none, but research and development cur-
rently underway in this area
beverage and pharmaceutical cellulose and glass fibers
filters
electrolytic diaphragms
Nafion membrane cell
PTFE
laminates
chemically treated papers
glass and ceramic papers
kraft papers
metal linings paper
versicore
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Asbestos-cement sheet use as cooling tower fill is rapidly decreasing
due to its potential for wear and fiber release under extreme conditions.
A wide variety of substitute materials are currently available for cooling
tower fill including polyvinyl and polypropylene plastics, cellulose,
aluminum, and steel. Metal substitutes are more durable; fire resis-
tant metal laminates are economical and are now on the marketplace. Fill
substitutes must be chemical resistant as well as flame resistant.
No substitutes for asbestos transmission-paper appear to be available.
For most applications any of the materials mentioned for cooling tower fill
substitutes are adequate. An alternative to asbestos electrolytic diaphragms
is DuPont's Nafion membrane mentioned previously. It consists of a film of
perfluorosulfonic acid resin (copolymer of tetrafluoroethylene) and another
monomer to which negative sulfonic acid groups are attached. Promising
results have also been obtained with a two-layer diaphragm polypropylene-
(PTFE). This cell has a resistance inside the electrolysis cell which is
comparable to that of asbestos. Tests carried out over a period of 1100 hours
did not show significant deterioration.
Economical, fire-resistant laminates that use chemically treated papers
as a laminated substrate and/or laminating resins containing flame-resistant
chemicals are available. Also, glass and ceramic paper substrates are used
when the extra cost is acceptable. For decorative laminates, asbestos papers
have been replaced by Kraft papers.
As for metal linings, H. H. Robertson Co. has produced "VerBicore," which
is manufactured in the same manner as their Galbestos sheetsiding which con-
tains asbestos paper, except that the asbestos paper lining is replaced with
a 3 mil thick layer of epoxy resin. Various types of specially painted sheets
can also be used as a siding substitute for Galbestos.
Substitute fibers which may be used in place of asbestos fibers in filters
include cellulose and glass. According to industry sources, these nonasbestos
substitutes have the durability of asbestos filters, but above grade 70 (an
indication of filter porosity), asbestos filters are more efficient.27,28
MANUFACTURING
Paper products are all made in similar processes, which can be represented
by the schematic diagram in Figure 2. Individual products may be the result
of additional manufacturing steps, as with roofing felt; the consequence of
different forming, as with millboard; or the outcome of varying raw materials,
as with specialty paper. By adjusting the percentages and types of asbestos
fibers, binders, and fillers, different semifinished products are formed.
Secondary processing, molding, cutting, or bonding is usually required to
attain the final product.
54
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RAW MATERIALS
STORAGE
PROPORTIONING
RECYCLED SOLIDS
WATER
RECYCLED WATER
WASTEWATER
MIXING
CLARIFICATION
(SAVE-ALL)
SLUDGE
STOCK CHEST
METERING
WATER
PAPER
MACHINE
STEAM
COOLING
~ COOLING WATER
^CONDENSATE
ORYING
STORAGE
CONSUMER
OR
ROOFING PLANT
Figure 2. Asbestos paper manufacturing operations.1*
55
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Primary Manufacture
The sequence of manufacturing steps is described for all products except
millboard/rollboard and beverage filters. This description is then followed
by a description of the unique features of millboard/rollboard and beverage
filter manufacture.
Raw Materials—
Asbestos paper generally contains from 70 to 95 percent asbestos by weight
with binders adding from 3 to 15 percent weight, and fillers making up the re-
mainder. A mixture of short chrysotile fibers, predominantly grades 5 through
7, forms the basis for the sheet. Starches, latex, corn gum, glue, and cement
are typical binders while cellulose fibers, rubber, clay, and rock wool may be
used as filler.
The exact formula of any product is frequently specified by the purchaser
to ensure that desired product qualities are obtained. In addition to varying
the percentage of asbestos in the final product, fillers and binders such as
mineral wool and fiberglass can be included to provide specific properties in
the final sheet.
Material Receiving—
Most manufacturers receive asbestos by rail in bundles of 25 or 50 100-
pound bags, bound together by a small amount of glue to minimize shifting during
shipping and slippage during handling. Bundles may be plastic stretch-wrapped
or shrink-wrapped to minimize fiber release and bag breakage. This concept
is relatively new and has only come into common use in the last 2 years. At
this time wrapping is a customer option.
Forklift trucks are used to unload the asbestos bundles into storage.
Other materials, such as wood pulp, rags, paper, and broke are commonly stored
in the same area.
Mixing—
In the mixing step, asbestos fibers are combined with water, binders and
fillers in a hydrapulper or beater. Depending on the product to be manufac-
tured, the asbestos may be dumped into the mixer in its original triple-wall
Kraft paper bag. For other products incapable of accepting organic material,
the bags are opened, emptied into the mixer, and disposed of in a sanitary
landfill.
After mixing, the slurry may be pumped through Jordan refiners, turbine-
like pieces of equipment that break down fibers and fiber clumps. At this
stage in the process, the stock typically contains about 3 percent fiber.
The stock will be further diluted to nearly 1/2 percent solids before being
applied to the machine.
56
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Paper Machines—
Two types of paper machines are used to manufacture asbestos paper:
Fourdrinier machines and cylinder machines. The difference occurs at the
machine's wet end, when the dilute slurry is formed into a paper sheet.
A Fourdrinier machine feeds a thin layer of refined stock onto an endless
moving wire screen. As the stock is carried away from the point of applica-
tion, water in the stock passes through the wire mesh, leaving a moist paper
sheet behind. In a cyclinder machine, stock is pumped into a vat containing
a screen-surfaced cylinder. A3 the cylinder rotates, a thin coating of fibers
collects on its surface while water drains through the screen. The fiber
coating is then transferred to a carrier felt moving across the top of the
cylinder. Depending on the desired thickness of the end product, one or more
cylinders may be required. The moving felt presses the damp layers together
as it passes over each successive cylinder, forming one damp sheet.
After the formulation stage, the two machine types are similar. Vacuum
boxes pull water out, and nip rolls squeeze out moisture until the sheet is
strong enough to leave the supporting felt and pass over a series of steam-
heated dryer rolls. As a final step, the sheet is "calendered" by passing
between two pressure rollers, producing a smooth surface.
Some paper products require no further processing other than trimming,
additional calendering or cutting to size. Of the nine product categories,
five fall into this category: commercial paper, flooring carrier, electrical
insulation paper, beater-add gasketing paper, and specialty paper.
Saturation—
Two product categories undergo a second processing step, asphalt satura-
tion. Both roofing felt and pipeline wrap are made as described above, but
pipeline wrap has glass fiber strands running lengthwise for strength. Hun-
dreds of bobbins feed a string-like glass into the wrap at some point in the
forming stage such that they are placed in the center of the product's thickness.
In the saturation step, diagranmed schematically in Figure 3, the paper
roll is unwound and passed through a bath of hot asphalt or coal tar until it
is thoroughly saturated. It may then pass over hot rollers to seal the asphalt
into the paper, followed by cold rollers to smooth the surface. Cooling water
may be sprayed directly onto the paper surface or a coating may be added to
keep layers from sticking when the material is rolled and packaged. In some
plants saturation is not a separate process but instead is the last step on
the paper machine.
Millboard and Rollboard—
Millboard production is in general similar to papermaking, but has a
number of important differences. Asbestos, binders and fillers, which vary
between manufacturers, are mixed with water to form a slurry. Millboard may
contain from 5 to 40 percent portland cement and starch. As binders, clay,
lime and mineral wool are used as fillers, particularly in applications not
exposed to high temperatures. The final product may contain from 70 to 95
percent asbestos by weight.
57
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HOT COAL TAR
OR ASPHALT
SATURATION 1
STEAM
COOLING
WATER
UNCOATED
ROOFING
COATING
COOLING
WATER
CONSUME^]
COOLING
UNWINDING
HEAT TREATMENT
ASBESTOS PAPER
STORAGE
ROLLS
CUTTING
ROLLING
PACKAGING
STORAGE
Figure 3. Asbestos paper saturation. 14
58
-------
The slurry is pumped to a vat where a rotating cylinder picks up a thin
coating of the mixture, in the same way that a cylinder paper machine picks
up paper stock. The thin sheet is drawn through a press for partial dewatering,
then wound continuously on a roller until the desired thickness is obtained.
The machine stops as workers cut the material built up on the roller lengthwise,
removing one thick sheet of damp millboard. Since the material is still moist,
individual layers adhere to each other in one thick sheet instead of separating
into thin, distinct sheets like those formed on a paper machine. The forming
process takes about 1 minute per sheet. Wet sheets go through a heat curing
step before being trimmed to standard sizes. The process is schematically
diagrammed in Figure 4.
Rollboard is a special type of asbestos paper with many of the same appli-
cations as millboard. Rolls of 1.59 mm (1/16-inch) thick paper are bonded to-
gether with sodium silicate to form a two—ply sheet, 3.18 mm (1/8-inch) thick.
Rollboard gets it9 name because it is sold in rolls, like roofing felt.
Beverage Filters—
Asbestos beverage filters are made on a conventional cylinder or Four-
drinier paper machine. Because demand for this product is low, the machine
is only used to produce beverage filters infrequently; for the most part, the
machine is employed to produce more popular products.
The major difference between asbestos beverage filters and other asbestos
paper products is the formula. Asbestos beverage filters may contain from 5
to 50 percent asbestos by weight, with diatomaceous earth, organic fiber, and
resins making up the remainder of the filter.
Manufacturing Plants
At present in the United States there are a limited number of manu-
facturers of asbestos paper products. The major companies have generally
broad product lines, producing several types of paper products. A plant will
usually produce a given product continuously for a period of time until demand
for that product is satisfied, then switch to the production of another pro-
duct. With the top five manufacturers accounting for more than 80 percent
of total production, the market can be characterized as highly concentrated.2
In Table 15 the principal manufacturers of asbestos paper products are
shown. The table also includes most plants, locations, capacities in tons/day,
type of papermaking machines, and paper products made.
There are two major producers of flooring felt: Armstrong Cork and
Congoleum Industries. Nicolet Industries of Ambler, Pennsylvania, and
Brown Company of Berlin, New Hampshire, made asbestos flooring felt in the
past, but terminated their production in 1980 and the mid-1970s, respec-
tively. 46,47 GAF Corporation formerly manufactured asbestos flooring felt
in Erie, Pennsylvania, but announced a commitment to end sales of asbestos
paper products effective April 1, 1980.48
There are two major domestic manufacturers of asbestos roofing felt:
Nicolet Industries and Celotex Corporation. The plants listed make base
59
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RECYCLED SOLIDS
WATER
DRYING
CONSUMER
TRIMMING
MIX ING
MACHINE
FORMING
FINISHING
STORAGE
CUTTING FROM
ROLL
RAW MATERIALS
STORAGE
If
Figure A. Asbestos millboard manufacture.
60
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TABLE 15. PRINCIPAL MANUFACTURERS OF ASBESTOS PAPER4'29"46
Coop any
Plant location
Plant
capacity
(ton/da?)
Machinery
Paper product mix
Ma op Bnginearlng
Milldale, CT
-
-
Beverage and pharmaceutical filter*
Armstrong Cork
Fultoo, NY
260
1
2
single cylinder, width 14C in.
fourdrlnler, width 88 and >62 In.
Flooring felt, gasket*
Boise Cascade
Beaver Falls, 8Y
-
-
Gasket papers
Celotex Corporation,
a Subsidiary of '
J la tfaltar Co.
| Lockland, OH
ZOO
3 single cylinder and 1 six
cylinder - width varies from
to 114 in., 1 Billboard
72
Roofing felt, pipeline wrap
millboard, rollboard, cooaercial paper
specialty paper
1 Linden, NJ
100
1
single cylinder, width 136
in.
Roofing felt, cooaercial paper
Cellulo
Fresno, CA
Sandusky, OH
-
-
)
Beverage and pharmaceutical filters
Colonial Fiber
Company
Covington, TN
Rochester, NH
Gasket papers, specialty paper
Specialty paper
Congoleua Industries
Cedarhurst, MD
260
2
2
single cylinder, width 120
fourdrlnler, width 120 and
and 168 in.,
204 in.
Flooring felt
Ertel Engineering
Kingston, NY
-
-
Beverage and pharmaceutical filter*
Filter Products Co.
(H6K Filters)
Richnond, CA
-
-
Beverage and pharmaceutical filter*
Hoilingsvorth
6 Vose
East Walpole, MA
45
1
1
six cylinder, width 120 in.
fourdrlnler, width 94 In.
Gasket papers
J ohoa-*Unv i 11 e
Hanvllle, NJ
Waukegan, IL
150
2
1
I
five cylinder, width 80 in.
single cylinder
six cylinder, width 72 in.
Gaaket papers, pipeline wrap,
specialty paper
millboard, rollboard, specialty paper
Hicolet Industrie*
Aabler, PA
so
1
2
four cylinder, width 80 in.
double cylinder, width SO a
nd 52 in.
Roofing felt, pipeline wrap
cwi-rclal paper, specialty paper
Quin-T-Corp.
Tllton, NH
-
-
Millboard, rollboard, electrical insulation
Rogers, Corp.
Rogers, CT
-
-
Gaskets
-------
felt which is later saturated with asphalt. Saturation plants are not neces-
sarily located at the sites where the base felts are made; manufacturers of
base felts may have a number of saturation plants.
Domestic manufacturers of beater-add gaskets include Armstrong Cork,
Bollingsworth & Vose, Boise Cascade, Colonial Fiber Company, Johns-Manville,
and the Rogers Corporation.39-41 Most gasket paper produced is sold to fabri-
cators who make the final consumer product. The 1978 edition of the Thomas
Register lists almost 200 fabricators of asbestos gaskets, but this includes
fabricators working with compressed sheet gaskets in addition to those working
with beater-add gaskets.
Manufacturers of asbestos pipe wrap include Nicolet Industries, Johns-
Manville and Celotex.^0,42 Nicolet is reported to be a much larger producer
of this product than is Celotex.30
Celotex, Johns-Manville and Quin-T Corp. manufacture asbestos mill-
board. 40,44,45 GAF discontinued production of asbestos paper and rollboard
as of April 1, 1980.^3,48 Nicolet has closed their Morristown, Pa., plant
but may still manufacture millboard elsewhere.44,46
Asbestos paper for electrical insulation is currently manufactured by
the Quin-T Corporation, formerly owned and operated by Johns-Manville.
Manning Paper and Nicolet Industries, which made insulation paper in the past,
no longer produce asbestos paper.44,49
Commercial paper is manufactured in the United States by Nicolet Indus-
tries and Celotex. Johns-Manville discontinued the manufacture of commercial
paper in April 1980.^0 Commercial asbestos paper is normally sold by the
manufacturer to independent distributors, converters and some original equip-
ment manufacturers. There are about 300 distributors and/or converter com-
panies in the U.S.29
The principal specialty paper manufacturers are Johns-Manville, Nicolet
Industries, Celotex Corporation and Colonial Fiber Company. They, in turn,
sell it to a wide variety of secondary manufacturers which use it to produce
consumer and industrial products.
ASBESTOS RELEASE
This section briefly summarizes the papermaking process, discusses the
asbestos content of asbestos paper products and reports estimates of work-
place fiber levels. Estimates of ambient fiber concentrations near manu-
facturing plants are also reported.
Emissions of asbestos fibers during production of the nine product cate-
gories may differ based on product friability, volumes produced, and plant
size. The nature of the actual production processes are very similar. Varia-
tions In emissions among plants manufacturing the same or similar products may
be a result of the type of control equipment, control practices, and general
cleanliness within the plant.
62
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Asbestos paper is essentially made by the same process used for organic
paper. Briefly, papermaking involves mixing or pulping the asbestos fiber with
water into a 1 to 3 percent slurry although dry mixing of the fiber and addi-
tives may precede the wet pulping. The wet stock slurry Is then fed onto either
a Fourdrinier or a cylinder paper machine. In both machines, paper forms on
screen surfaces that draw the water away as the pulp is carried forward, forming
a wet mat. This wet mat is conveyed through steam-heated dryer rolls. After
drying, the paper may be cut into sheets or collected in rolls. This basic
process is the same for nearly all paper products.
In addition to the product use or method of manufacture, asbestos products
differ according to the amount of asbestos and other substances in the product.
•The asbestos content of the finished paper may vary from 5 to essentially 100
percent, although 70 to 95 percent is most common. The binder content in paper
usually consists of 3 to 15 percent of its weight. Starches and elastomers are
the two major binder groups. Less frequently used binders may include glue,
cement, and gypsum. The specification of the amount of asbestos and the type
of binders plus other special substances depends on the desired properties and
intended uses of the final product. Constituents such as mineral wool, fiber-
glass, cellulose, and latex may be used to impart special properties.
Clearly, workplace fiber levels at any stage in the manufacturing process
will be affected by the asbestos content of the final product. The higher the
asbestos content, the higher the potential exposure. Thus a plant producing
gasket paper that is 90 percent asbestos by weight will have much higher ex-
posure levels than a plant producing beverage filters containing 10 percent
asbestos by weight, given that both facilities use the same process and controls.
Input/Output
Figure 5 shows estimates of process and disposal emissions for the asbes-
tos paper manufacturing industry. These figures are based on Levine's^1 1974
estimates of air emissions and solid waste generated by the manufacturing
process. Estimates by Meylan52 were used to determine water emissions. All
data were projected to 1980 U.S. Bureau of Mines1 consumption figures. Poten-
tial sources of air emissions include fiber introduction, stock operation,
drying, cutting, rolling and trimming while water emissions originate at the
paper machine. Of the estimated 90,020 metric tons of raw asbestos fiber en-
tering the process, approximately 85,474 metric tons are incorporated into the
product. Of the remaining 4,546 metric tons, 4,451.5 m.t. are sent to disposal
as sludge, product scraps and as vacuum cleaner and baghouse dust. Approxi-
mately 45 metric tons escape through an air emissions control device (typi-
cally a baghouse) while another 45 m.t. escape in wastewater discharged from
a clarifier. Levine's^l atmospheric emissions estimates are based on gross
assumptions with a reported uncertainty of at least an order of magnitude.
Meylan's^2 estimates of atmospheric emissions are generally 1 to 3 orders of
magnitude lower. Meylan's estimate of asbestos in paper product wastewater
is based on a clarifier efficiency of 96 percent. Atmospheric emissions from
disposal, based on GCA estimates, are shown to total 4.5 metric tons per year
for the paper products industry. This estimation is loosely based on Levlne's
data and takes into account new regulations adopted in 1974 regarding the dis-
posal of asbestos.
63
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WWUFACmiitt O^fRATIONS
ItfTMPUCTtOft
'gAGHOUSE WtSStOW
J *5 TPY
WATER
cm ssi cms
RANUfACTUR INC
P*0C«SES
M5K* TPY
CONTROL EQUIWEJfT
ULTIMATE DEPOSIT)OA
SOLID
WATER
Note: TPY - metric tons per year.
Figure 5. Input/output estimates for the asbestos paper industry (metric tons).
-------
During Manufacture
Workplace Exposure—
Fiber concentrations In a papermaklng facility vary from work station to
work station, depending on whether or not the asbestos is wet or dry, whether
or not it has been in contact with binder* and also depending upon the ongoing
physical process. Table 16 shows time-weighted average fiber counts at dif-
ferent stages in the papermaklng process. This table was extracted from
asbestos industry figures and includes their engineering estimates on typical
fiber counts. These fiber counts are discussed individually in the remainder
of this section.
TABLE 16. TIME-WEIGHTED AVERAGE FIBER COUNTS -
ASBESTOS PAPER PRODUCTS3»53
Fiber count*3
Range
Typical
Process step
(fibers/cc)
(fibers/cc)
Receiving and storage
0.25 - 2.5
1.0
Fiber introduction
0.3 - 2.8
1.9
Stock preparation
0. i - 2.7
1.2
Papermaklng
0.25 - 1.0
0.8
Drying
0.5 - 1.5
0.8
Slitting and calendering
0.L - 1.6
1.0
Rewinding
0.5 - 1.5
1.0
^ased on plants representing 53 percent of asbestos
paper Industry production.
^Optical-microscope visible fibers.
Receiving and storage—Asbestos fiber is transported to manufacturing
plants predominantly by railcars, although some plants receive deliveries by
truck. The asbestos, packed in 100-pound bags, is unloaded by forklift trucks
and placed in storage until needed. Since receiving and storage activities
are the same for all asbestos products, it is valid to use data from all pri-
mary asbestos industry segments in estimating fiber levels.
A survey of all primary asbestos industry segnents showed a range of ex-
posures in receiving and storage from 0.25 to 2.5 fibers/cc TWA, with 1.0
flbers/cc TWA considered typical.53 High fiber counts are a result of bag
breakage during shipping, careless unloading, and Ineffective cleaning. The
use of plastic shrink-wrap for bundles of 25 bags can reduce emissions due to
breakage, but may increase fiber levels at a later stage, when the plastic
wrap must be removed.
I
65
%
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Fiber Introduction—Another processing step common to all primary asbes-
tos industries, the introduction of raw fiber into the process, can result in
high fiber levels. Individual bags may be opened either manually or semi-
automatically and the contents dumped into a stock preparation tank of some
type or the entire bag may be dumped into stock preparation unopened. In the
manual system a worker lifts the bag and slits it open with a knife; in the
semiautomatic system a conveyor may be used to move the bags and/or a blade
mechanism may be used to open the bags. The empty bags, although generally
handled carefully prior to disposal, can be a source of significant fiber
amounts.
An industry survey indicated that a typical exposure at this stage of the
production process would be 1.9 fibers/cc TWA, with actual values ranging from
0.3 to 2.8 fibers/cc TWA.^3 Almost all fiber introduction stations are equipped
with exhauBt hoods that collect any dust generated and duct it to an emission
control device such as a Ducon system or a baghouse, to the atmosphere, or to
another part of the process.
Stock preparation—After the asbestos fiber has been dumped into a
hydrapulper or beater, the asbestos along with cellulose material, binders
and fillers, is wet mixed to achieve a specified concentration and consistency.
In most plants, fiber introduction and stock preparation take place in the
same piece of process equipment; in some plants a separate step is required.
For plants with separate fiber introduction and stock preparation steps,
fiber counts ranged from 0.1 to 2.7 fibers/cc TWA, with 1.2 fibers/cc TWA
reported to be a typical value.^3
Papermaklng—Stock slurry from the preparation step is pumped into a
holding tank prior to use. From the holding tank, the slurry flows to the
paper machine where it is formed into a sheet, either on a Fourdrinier or a
cylinder-type machine. In either case, the high moisture content causes low
fiber release during this stage. Exposure levels of 0.25 to 1.0 fibers/cc
TWA are reported. Typically, 0.8 fibers/cc TWA can be expected.^3
Drying—After the paper is formed, the wet pulp is press rolled to
remove excess water and routed through steam-heated dryer rolls to attain
the desired final moisture content. Although the high moisture content at
the wet end of the drying process (75 to 99 percent) minimizes emissions at
the dry end of the product, moisture level is reduced (5 percent) and some
dust exposure may result.
Exposure levels during drying have ranged from 0.5 to 1.5 fibers/cc TWA
with 0.8 fibers/cc TWA considered typical.53
Slitting and Calendering—After drying, the wide paper sheet formed by
the machine passes to a cutting and slitting area where it is cut into
narrower rolls according to customer specifications. The paper may also pass
through some pressured rolls, called calender rolls, to achieve a smoother
surface finish.
66
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Asbestos fiber levelB at this stage have been measured ranging from 0.1
to 1.6 fibers/cc TWA. A typical value would be 1.0 fibers/cc TWA.53
Rewinding—The rewinding step Involves bulk packaging of paper products
on spools or rolls in preparation for shipping. Usually, very little cutting
is required at this stage but the winding process can generate fiber release.
Exposure levels measured in rewinding are typically 1.0 flbers/cc TWA, but
have ranged from 0.5 to 1.5 flbers/cc TWA. 53
Secondary fabricator industries—Secondary processors or fabricators
are firms that purchase products from one or more segments of the primary
industry and either fabricate these materials or process then together with
other materials into an end product. While some products undergo further
processing beyond a secondary stage, the amount of additional activity is
minimal. For the most part asbestos paper products go from either primary
manufacture or secondary processing to an end use such as a construction
company or the automotive aftermarket and repair industry. In general, opera-
tions involved in secondary fabrication are quite similar to the finishing
operations in primary manufacturing segments. They may utilize such opera-
tions as grinding, sawing, sanding, punching, pressing, or splitting,
depending on the fabricated product desired.
It is estimated that 60 percent of asbestos paper goes through some form
of secondary fabrication before reaching the end uaer.^J Typical finishings
operations Include slitting, sawing, punch pressing, converting, and lami-
nating and typical asbestos exposure ranges have been estimated at 1.0 to
3.5 fibers/cc.^
Primary manufacturers of sheet packing sell a pressed gasket material to
secondary manufacturers or gasket cutters. Secondary fabricators cut, split,
or punch the material to specific shapes for each end use. During these sec-
ondary fabrication processes, the packing or gasket materials may be impregnated
with polymers, latex, or other chemicals to impart certain properties to the
materials. Gasket cutters may use asbestos paper when strength and pressure
sensitivity are not critical, whereas asbestos yarns may be used for packing
materials for pumps and other applications which require high strength materials.
Exposure ranges for packings and gaskets have been reported at 0.2 to 5.0 fibers/
cc TWA.53
Worker exposure—Using assumptions put forth by Suta and Levine,^ we
can estimate that a person exposed to the maximum permissible asbestos con-
centration of two optical-microscope-viaible fibers/cc greater than 5 ym over
a 40-hour week will inhale 125 billion electron-microscope-visible fibers
annually. As demonstrated in Table 16, production workers in the asbestos
paper manufacturing industry are typically exposed to i fibers/cc >5 pm53 and
can be expected to inhale approximately 62.5 billion electron-microscope-
visible fibers per year, compared to 6.25 million fibers Inhaled for persons
exposed to the median ambient urban concentration of 1 x 10~4 fibers/cc
>5 ym.
67
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Emissions to Air—
Johns-Manvllle Corporation sampled ambient fiber levels near seven plants
during the period 1969 through 1971. Results of this study are sixmnarized in
Table 17. While neither the test method nor the type of asbestos fibers mea-
sured were noted in this data summary, it does provide a relative measure of
ambient fiber concentrations near asbestos product manufacturing facilities.
It is important to note that these plants do not produce asbestos paper
products solely. The Waukegan and Manville plants manufactured asbestos-
cement pipe, sheeting* and other products, in addition to paper produced
during the sampling interval. Overall, reported ambient fiber levels are low,
approaching the lower detection limit of the sampling equipment. With one
exception, the asbestos fiber levels measured are less than or equal to the
median ambient air urban exposure of 20 ng/m^. These data would also appear
to indicate that asbestos emissions from industrial facilities do not signifi-
cantly increase ambient levels of asbestos fibers.
Emission measurements and subsequent modeling of an asbestos paper plant
by GCA/Technology Division in 1979^5 contradicted the Johns-Manville results.
Samples taken from general vents between paper machines and hydropulper vents
showed typical fiber concentrations of 25 and 90 f/cc, respectively. By com-
bining this fiber concentration data with process aspiration rates, fiber
emission rates were estimated and employed In EPA's PTMTP Point Source Disper-
sion Program. This Gaussian plume model was used to model the dispersion of
airborne asbestos emanating from the facility. Six modeling runs were per-
formed for various stability classes and wind directions. The results of the
dispersion modeling showed that, in general, plant related concentrations
above 0.05 f/cc, as measured by an electron microscope, may be encountered
within 500 meters of the plant, depending on the meteorological conditions
present. This plant-related exposure is more than twice the median urban ex-
posure of 20 ng/m^ and exceeds the State of Connecticut's proposed ambient
standard of 30 ng/m^. These ambient levels, as estimated by the dispersion
model, are close to values actually measured by a low volume sampler near
four industrial users of asbestos in the State of Connecticut (values greater
than 30 ng/m^ were measured).
GCA/Technology Division employed personal sampling pumps with 0.4 nm size
Nuclepore filters of 37 mm diameter housed in an open-faced holder to take
the samples at a rate of 1.5 1/min. The sampling was not done isokinetically,
and therefore, the validity of the data is questionable. Nonetheless, it is
felt that the accuracy of the data is sufficient to provide approximate emis-
sions of asbestos fibers into the ambient air. Table 18 details the location
and corresponding fiber concentration for each sample taken at the asbestos
paper plant.
Suta and Levine^ have estimated the average atmospheric asbestos con-
centration within 5 km of asbestos paper manufacturing plants to be 33 thousand
electron-microscope-visible fibers per cubic meter with an estimated 180 million
fibers being inhaled by the average person annually. This compares to their
estimates of 27.A million electron-microscope-visible fibers being inhaled by
persons exposed to the average ambient urban fiber concentration of 5,000
fibers/m^ and 125 billion fibers being inhaled by workers exposed to the maximum
allowable concentration of 2 million fibers/m^ >5 um.
68
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TABLE 17. AMBIENT ASBESTOS FIBER LEVELS REPORTED BY JOHNS-MANVILLE
FOR SAMPLING DONE IN 1969-197157
Sample location
Ambient asbestos level®
(fibers/cc)
Total
>5y
Lompoc, CA
Employee backyard
0.05
0.02
North Plainfield, NJ
Employee backyard
0.02
0.02
Nashua, NH
Plant yard
0.02
0.02
Plant yard
<0.01
<0.01
Employee backyard
<0.01
<0.01
Employee backyard
<0.01
<0.01
Waukegan, IL
South property line
0.02
<0.01
Somerville, NJ
Employee backyard
0.02
0.01
Scotch Plains, NJ
Employee backyard
—
0.02
Manville, NJ
1,000 ft south east
0.02
<0.01
1,000 ft south east
0.02
<0.01
^est method not reported; data should only be used for relative
fiber concentrations.
69
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TABLE 18. SAMPLING RESULTS OF AN ASBESTOS PAPER PLANT (1979)a»55
Sample Pump Asbestos fiber
Filter duration flow concentration
number Location (min) (1pm) (f/cc)b
c-f>
Below #4 pulper vent (two
batches made)
60
1.5
144
C-3
Below //3 pulper vent (one
batch made)
60
1.5
10
C-2
Below ffl pulper vent (two
batches made)
60
1.5
48
C-5
In exhaust vent, it3 pulper
(one batch made)
55
a
49
C-4
In exhaust vent, ill pulper
(two batches made)
55
a
84
C-l
In exhaust vent #4 pulper
(two hatches made)
50
a
91
Oil
Vent between til and itl
paper machines - wet end
vent
60
1.5
25
C-12
Vent between 01 and 02
paper machines - second
vent from wet end
60
1.5
22
C-8
Topmost catwalk, heat ex-
changer on wet end of it2
paper machine
60
1.5
1.0
C-9
Same as C-8
60
1.5
1.8
C-14
South end of paper machine
building roof, on ridge
between machines
60
1.5
0.31
C-l 3
40 feet west of C-14
60
1.5
0.54
C-15
40 feet east of C-14
60
1.5
0.38
C-16
2 feet west of vacuum pump
65
1.5
0.15
exhaust, wet end of #1
paper machine
0
Samples in vents were clogging due to high moisture content. Pumps
were shut off after approximately 30 minutes of sampling although
the open-face samples were kept in the vents for the remainder of
the sampling period.
^Scanning electron microscope analysis.
70
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Release to Water—
As paper products manufacturing is a wet process, substantial amounts
of asbestos fibers are discharged in the plant process effluent streams.
It has been estimated'1 that the raw water discharge from a typical asbestos
paper manufacturing process contains about 19 pounds of suspended solids per
ton of product produced (9.5 kg/m.t.). Furthermore, Meylan 2 estimates that
approximately 80 percent of paper products suspended solids are asbestos
fibers, since this is the average asbestos content of the paper produced. This
raw wastewater stream is directed to onsite clarifiers for solids removal.
The efficiency of industrial clarifiers with respect to asbestos particles is
not available. Meylan^2 estimates that this efficiency may range from 94 to
96 percent. If the 94 percent clarifier efficiency is used in conjunction with
the other factors, and they in turn are applied to the 1980 paper products
asbestos consumption rate of 90,020 m.t. per year, we can estimate an asbestos
release to water of approximately 39 m.t. per year.
Suta and Levine514 use different factors to arrive at similar waterbome
asbestos emission estimates. They assume that approximately 34 pounds of
asbestos suspended solids are discharged to clarifiers per ton of asbestos
consumed (17.0 kg/m.t.). To this value, they apply a clarifier removal
efficiency of approximately 97 percent. Using these factors and 1980 asbestos
consumptions, we can calculate an asbestos release to public waters of approxi-
mately 45 m.t. per year. While this emission rate is only slightly higher
than that calculated using Meylan1s rationale, the amount of asbestos removed
in the clarifiers and subsequently disposed of on land is more than two times
as great.
To maintain a consistency of approach in this report with regards to
emission estimates for each product category, GCA has utilized the Suta and
Levine estimates. As demonstrated in Figure 5, these translate into an
asbestos water emission of 45 m.t. per year.
Releases to Land—
Solid waste from paper products manufacturing is essentially all in the
form of baghouse catch and clarifier sludge. Rejected papers, scraps, and
trimmings are apparently not wasted in significant amounts, as this waste
paper can usually be returned to the beater and repulped for recycling.52
The quantity of sludge collected in the clarifiers has been estimated using
rationale developed by Suta and Levine54 and upgraded to 1980 asbestos con-
sumption figures. This estimated totals 1486 m.t. of sludge per year. In
general, most of the suspended solids (sludge) collected from clarifying
units or ponds are disposed of in landfills. To this quantity is added the
asbestos captured in baghouses. These baghouses control the principal asbestos
fiber introduction and transfer stations. Their asbestos fiber control effi-
ciency is estimated to be 99.9 percent. The baghouse catch adds an additional
2970 m.t. per year of asbestos which is ultimately landfilled, for a total of
4451.5 m.t. per year. Of this amount, approximately 0.1 percent or 4.5 m.t.
will escape to the atmosphere due to reentrainment of asbestos during land-
filling. This estimate was also derived from Suta and Levine projections,
upgraded to account for 1980 asbestos fiber consumption. The actual degree
or reentrainment will largely depend on the care with which the dry asbestos
fibers captured in the baghouses are properly landfilled and covered.
71
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During Use
Asbestos fibers are encased in all asbestos paper products by some type
of binder. They will be released to the atmosphere only when this binder is
disturbed, as during product installation and removal, or in the course of
natural wear due to the effects of use and age. While no monitoring data exist
to support the concentration estimates of asbestos released during installation
of an asbestos paper product, these quantities are thought to be mimimal.51 as
is the case for most asbestos products, the predominant amount of asbestos fiber
content is wasted to landfills when product replacement is done. The effect
of "wear and tear" on asbestos fiber release varies with the individual paper
product. The two principal asbestos paper product categories, flooring felt
and roofing felt, have a double protection. The asbestos fiber is first en-
capsulated in a strong binder, and then the asbestos paper is covered with
an additional product (vinyl flooring or asphalt roofing) which screens it
from direct wear. Both of these products have extended lifetimes (10 to 25
years), and the annual asbestos release would be minimal. The other paper
products, including pipeline wrap, gaskets, insulation, specialty and com-
mercial papers and beverage and pharmaceutical papers, have a more direct
contact with ambient conditions. In these applications, asbestos fibers can
be either released to the air or leached into the ground due to extreme en-
vironmental exposure. No ambient monitoring data exists to verify this sup-
position; however, Suta and Levine^ have made overall estimates on the amount
of asbestos released to the air due to the use of asbestos paper products.
When upgraded to account for 1980 paper products asbestos consumption, this
estimate totals 9.7 m.t. per year. Neither the rationale nor the calculations
used in this estimate was presented.
During Disposal
Maintenance and replacement of asbestos paper products account for
approximately 72 percent of annual production and annual asbestos use.54
Using 1980 consumption figures, this amounts to approximately 61,200 m.t.
of asbestos. This asbestos is bound in a matrix by a binder and is unlikely
to be released to the environment. In some cases, as in roofing felt, the
used asbestos product may be left in place and covered with its replacement.
In most applications, however, the discarded asbestos is collected and de-
posited in a landfill or sent to an incinerator. Certain paper categories,
including pipeline wrap and muffler paper, may be exposed to extreme con-
ditions. The binder in these papers may breakdown from long-term use,
thereby causing the material to be friable. This possibility has not been
substantiated by ambient monitoring, however. Airborne asbestos release
that can be attributed to the disposal of used paper products is estimated
to total 11.3 m.t. per year, based on 1980 asbestos fiber consumption.
CONCLUSIONS
The asbestos paper products sector is a diversified collection of goods
which share a common production technology. Each product category is unique
in its historical trends, availability of substitutes and projections for
72
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future growth. Collectively, this sector Is In a static growth mode, with
some categories showing modest annual Increases, while most exhibit level
or slightly decreasing asbestos consumption. An examination of each paper
category will serve to review the current situation on a case-by-case
basis.
Flooring Felt
Although asbestos flooring felt is in a high consumption category,
future growth is expected to diminish?? due to a stabilization of the
product mix because the changeover (which has been occurring in the recent
past) from jute backing to the newer asbestos backing is nearly complete.
This means that the asbestos product has now replaced the jute in most
every application. From 1971 through 1975, growth of the asbestos backing
was estimated at 14.8 percent annually, whereas the same source projects that
the annual growth through 1980 will be 5 percent and only 2.9 percent from
1980 to 198S. The market currently backs this up with a small positive
growth rate. In addition, new substitutes to the asbestos product, par-
ticularly foam cushion backings and backless sheet flooring, are providing
increasing competition for the asbestos flooring felt market, indicating
that there may well be yet another transitional growth stage at some time
in the future, with the development of suitable alternatives.
Roofing Felt
Industry sources believe that the asbestos roofing felt market is currently
stable, but a decline is expected in the near future for two major reasons.
First, asbestos roofing is beginning to feel competitive market pressures from
fiberglass roofing and, second, labor unions and the construction industry are
becoming more apprehensive about using asbestos products. Fiberglass has
many of the same technical advantages and characteristics as asbestos and is
less expensive for initial installation. Furthermore, fiberglass requires less
saturation than asbestos and as petroleum and asbestos prices climb the cost
differential between fiberglass and asbestos roofing will shift more and more
in favor of fiberglass. However, asbestos roofing is considered more durable
than fiberglass, possibly making asbestos more cost effective in the long run.
Arthur D. Little?® expected demand for asbestos roofing to decline at an
average rate of 2.8 percent through 1980 and by about 5 percent from 1980 to
1985. Industry sources feel the actual decline will be slightly less.
Beater-Add Gasket
A marginal increase is projected for asbestos gasket substitutes. Other
asbestos paper categories seen more prone to substitution than gaskets. How-
ever, this may be subject to change as substitute products are developed.
Industry contacts^ pointed to the fact that substitutes are often not used
by industries due to their expense, but if concern over the use of asbestos
products grows, this attitude could change. Currently, this paper category
is enjoying perhaps the least competition from substitute products.
73
-------
Pipeline Wrap
Saturated asbestos pipe wraps are presently the preferred corrosion pro-
tection system lor oil and gas pipelines due to their time-tested durability
and relatively low cost. However, the market for pipeline corrosion protec-
tion is competitive and alternatives to asbestos felt are available.
As might be expected, potential growth in demand for asbestos pipe wrap
(or substitutes for it) is a function principally of new pipeline construction
and availability of competitive materials.29 Hew pipeline construction has
historically experienced rapid growth and this is expected to continue. Com-
petitive alternatives to asbestos wrap, which are becoming more available*
will most likely exert some downward pressure on the growth of the asbestos
wrap market.
At present, most industry sources view the asbestos pipeline wrap market
as stable; however, in the near term, a slight downward shift of the market
can be expected, primarily due to the competitive pressures of the relatively
new fiberglass pipe wraps and new epoxy resins and extruded coatings that are
Just becoming commercially available. Coat effectiveness still favors asbestos
pipe wraps; however, with the rapidly rising costs of asbestos fiber and petro-
leum products (asphalt and coal tar), the advantage may shift away from
asbestos.
Millboard
Substitute millboard products have been developed to meet the variety of
temperature, corrosion, and other environmental conditions imposed on the
asbestos product. Thus, asbestos millboard production is not expected to in-
crease significantly in the future. The annual growth rate for asbestos mill-
board and commercial papers is projected to be only 0.9 to 1.0 percent through
1985,29 but it is anticipated that U.S. firms producing millboard will cease
production of the product as acceptable, economical substitutes are de-
veloped. 59 industry is likely to maintain minimal production capacity for
specific applications where alternatives are not available. Because alter-
natives, particularly in heat and flame protection applications, are becoming
available, asbestos millboard production may decline in the future. Sub-
stitutes for millboard gasket applications are not presently available; there-
fore, this market segment Is presently very stable.
Electrical Insulation
Transformer manufacturers are constantly using more substitutes for asbes-
tos electrical insulation papers. Nomex papers are already extensively used
by electrical and transformer manufacturers,7 while Fiberfrax and other re-
placement industrial laminates are already on the market. Therefore, the
market for asbestos electrical paper is declining, although the rate of decline
is not known at present. The market for substitute products such as Nomex
paper has been steadily growing since it came on the market in 1965.^0
74
-------
Commercial Papers
The overall growth rate for asbestos commercial paper is slightLy nega-
tive and is not expected to change, indicating that substitute products will
have an opportunity to establish themselves in this area. Asbestos muffler
paper has already been replaced by ceramic and glass papers in the United
States, apparently due to concern exhibited by automotive muffler and conver-
ter producers about using asbestos-containing materials. As for corrugated
paper, the current outlook indicates that it may not be made in the future.
Substitute products like ceramic paper can replace asbestos commercial paper
in the future if the greater cost of such products is accepted.
Specialty Papers
Saturated asbestos paper is becoming too expensive compared to the readily
available plastic substitutes for cooling tower fill;13 thus the market should
favor replacement of asbestos fill presently in use with substitute products.
However, in specialty applications, such as cooling for gaseous diffusions,
asbestos fill is used rather than other materials because of its superior heat
and chemical resistant characteristics. The use of asbestos-cement sheet as
a cooling tower fill is rapidly decreasing due to its potential for wear under
extreme pH conditions creating a potential health risk. Nonmetal fills are gen-
erally lighter than metal fills and, therefore, have advantages in transport
costs and handling ease. Asbestos paper is considered the best fill material
in terms of chemical and heat resistance, but for most applications, the extra
chemical and heat resistance is not critical. As indicated, plastic fills are
becoming the most popular for general applications.
Many of the products developed to replace the other asbestos specialty
papers seem to be readily available. The only exception is transmission paper
where there are currently no nonasbestos alternatives available, although
research and development is underway in this field. In electrolytic diaphragms,
substitutes exist, but are not equal to asbestos in properties and quality.
Nonasbestos products have already replaced asbestos in many filter papers and
industrial laminates, and comparably priced nonasbestos metal lining paper is
increasing in market share. There remain some deficiencies to correct; research
in such areas as disposal and handling of spent paper generated in electrolytic
chlorine production may also be desirable. Some asbestos specialty papers are
already being produced in lower volumes. With the many alternative products
available, this category appears to have the potential for rapid reductions in
asbestos con simp t ion.
Beverage Filters
Asbestos beverage and pharmaceutical filters are not only produced and
consumed in very small amounts, but also will likely be totally replaced with
available substitutes in the not-too-distant future. However, as this is only
a small segment of the asbestos paper products industry, it is unlikely to
have any great effect. It has been concluded61 that nonasbestos filter
sheets have reached the stage where they can be considered a full substitute
for asbestos filters. Further,*8 the comparative economics may favor the
75
-------
nonasbestos filters since the filtering efficiency of the nonasbestos sheets
in some applications is considered equal to that of asbestos. However, for
haze removal from beverages, asbestos appears superior at present and some
beverage manufacturers still require this quality.19
The major advantage of asbestos use in the past was its high positive
charge which attracts negatively charged ions. In pharmaceuticals, bacteria
must be removed from products, and since most bacteria have negatively charged
ions, only asbestos filters were able to attract such ions. However, newly
developed products can receive such a charge and consequently act similarly.
Overall, the trend for asbestos paper products is in a state of flux.
Almost all categories show a stable or marginal decrease in the amount of
asbestos to be used. Only in those instances, such as gaskets and some
specialty papers, where the specific qualities of asbestos are absolutely
essential, is there a slight increase in asbestos consumption predicted.
This "leveling off" of asbestos use is generally attributed to the availability
of an acceptable, if not completely identical, alternative. Changes in
substitute quality and availability will directly affect asbestos use in the
paper products sector.
76
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REFERENCES
1. Clifton, R. A. Asbestos. 1980 Minerals Yearbokk. U.S. Bureau of
Mines. Washington, D.C., 1981.
2. Meylan, W. M., P. H. Howard, and A. Hanchett. U.S. Asbestos Paper In-
dustry and Substitutes for Asbestos Paper and Asbestos Brake Linings.
U.S. Environmental Protection Agency, Washington, D.C., September 1979.
3. John8-Manville Corporation, Manual for Built-up Roofs, 1978.
4. Carton, R. J. Development Docunent for Effluent Limitation Guidelines,
Building, Construction, and Paper Segment of the Asbestos Manufacturing
Point Source Category. EPA-440/l-74-017-a, U.S. Environmental Protec-
tion Agency, Washington, D.C., February 1974.
5. Telecon. Sales Personnel, Carborundun Corporation, Niagara Falls, N.Y.,
with 0. Ramsay, GCA Corporation, August 1979.
6. Pye, A. M. A Review of Asbestos Substitute Materials In Industrial
Applications. Journal of Hazardous Materials (Netherlands) 137-138.
7. Telecon. Hayman, J. Technical Service Representative, DuPont, Wilmington,
DE, with Syracuse Research Corporation, July 1979.
8. Telecon. Hughes, N., Quin-T Corp., Tllton, N.H., with Syracuse Research
Corporation, July 1979.
9. Telecon. Wllmore, R., National Electrical Manufacturing Association
(NEMA), Washington, D.C., with Syracuse Research Corporation, August
1979.
10. Lewis, B. G. Asbestos in Cooling Tower Waters. Argonne National Lab-
oratory, Argonne, 111., NT1S No. ANL/ES-63, December 1977.
11. Clifton, R. A. Asbestos. Preprint from Bulletin 667, Mineral Facts
and Problems. 1975 ed. U.S. Department of Interior, Bureau of Mines,
1975; and Personal Communication with SRC, 1979.
12. Telecon. Lai, M., Hooker Chemical Company, Niagara Falls, N.Y., with
SRC, August 1979.
13. Telecon. Skold, J., Munters Corporation, Fort Myers, Fla., with SRC,
August 1979.
77
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14. Deutsch, Z. C., C. C. Brumbaugh, and F. H. Rockwell. Alkali and Chlorine.
Kirk-Othmer Encycl. Cheat. Tech. (2nd ed.), _U 681-699, 1963.
15. Dahl, S. A. Chlor-Alkali Cell Features, New Ion-Exchange Membrane.
Chemical Engineering. August 18, 1975. p. 60-61.
16. Telecon. Cannady, 1)., Westlnghouse Corp., Hampton, S.C., with SRC,
August 1979.
17. Cannady, D. Decorative Laminates. Modern Plastics Encyclopedia, 77-78;
pp. 124-125. Published in conjunction with Modern Plastics, Vol. 54.
No. 10A, NcGraw-Hill Publication. October 1977.
18. Held, R. Nonasbestos Filter Sheets. The Brewers Digest, December 1978,
pp. 38-42.
19. Telecon. Varleriote, S., Cellulo Co., Fresno, CA, with SRC (Syracuse
Research Corporation), July 1979.
20. Belcher, Louis, GAR Corporation, letter of Joni Repasch, EPA OTS,
February 7, 1980.
21. Johns-Manville, Fact Sheet for GlasPly Builtup Roofing Systems, 1979.
22. Telecon. Reznic, B. Applications Engineer, Cotromics Corporation,
3379 Shore Parkway, Brooklyn, N.Y., (212) 646-7996, with M. Shah, GCA
Corporation, September 1979.
23. (PWC) Carborundun Corporation. Fiberfrax 110 Paper Product Specifica-
tions. March 1979.
24. Anonymous. Nomex Aramid. Bulletin NX-7, published by DuPont, Wilmington,
Del. November 1977.
25. Carborundum Corporation. Fiberfrax Ceramic Fiber.
26. Masonite Corp. Benelex 402 Physical Properties.
27. Telecon. Lavery, F., Sales Manager, Ertel Engineering Company, Kingston,
N.Y., (212) 226-6023, with M. Shah, GCA Corporation, September 1979.
28. Telecon. Gusmer, J., President, Cellulo Company, Waupaca, Wisconsin,
with M. Shah, GCA Corporation, (715) 258-5526, September 1979.
29. Arthur D. Little, Inc. Characterization of the U.S. Asbestos Paper
Markets. Prepared for the Ministry of Industry and Commerce -
Government of Quebec, Canada, Report C-79231, 1976.
30. Wright, M. D., et al. Asbestos Dust Technological Feasibility Assessment
and Economic Impact Analysis of the Proposed Federal Occupational
Standard: Part I. U.S. Department of Labor, Occupational Safety and
Health Administration, Washington, D.C., September 1978.
78
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31. Gregg, E. T. Development Document for Effluent Limitations Guidelines
and New Source Performance Standards for the Textile, Friction Materials
and Sealing Devices Segment of the Asbestos Manufacturing Point Source
Category. EPA-440/l-74/035a, Group 1, Phase II, U.S. Environmental
Protection Agency* Washington, D.C., December 1974.
32. Chapman, J. H., D. E. Matzzie, and R. G. Hillman. Asbestos Dust -
Technological Feasibility Assessment and Economic Impact Analysis of
the Proposed Federal Occupational Standard, Part III, Technical Appendices,
Asbestos and Health Administration, Washington, D.C., September 1978.
,33 Telecon. Don Wheaton, Cellulo Co., Fresno, CA, (209) 485-2692, with
Anne Duffy, GCA Corporation, GCA/Technology Division, April 17, 1981,
Call No. 27.
34. Telecon. Mr. Hallet, Ertel Engineering, Kingston, N.Y., (212) 226-6023,
with Anne Duffy, GCA Corporation, GCA/Technology Division, April 17, 1981,
Call No. 28.
35. Telecon. Company Representative. Alsop Engineering, Killdale, Conn.,
(203) 628-9661, with Anne Duffy, GCA Corporation, GCA/Technology Division,
April 17, 1981, Call No. 30.
36. Anonymous. World Wide Directory of Products and Operations 1979. Pub-
lished by Johns-Manville Corp., 1979.
37. Telecon. Davies, H., Nicolet Industries, Norristown, Pa., with Syracuse
Research Corporation, July 1979.
38. Syracuse Research Corporation. Communications to GCA/Technology Division.
August-September 1979.
39. Telecon. Pat Thurber. Colonial Fiber Company, Division of Lydall Corp.,
Manchester, Conn., (203) 646-1233, with Anne Duffy, GCA Corporation/
Technology Division. April 14, 1981. Call #9.
40. Telecon. Mrs. Loretta Ferguson. Johns-Manville Corp., Denver, Colo.,
(303) 979-1000, with Anne Duffy, GCA Corporation/Technology Division.
April 13, 1981, Call #2.
41. Telecon. Dot Hebert. Rogers Corp., Rogers, Conn., (203) 774-9605, with
Anne Duffy, GCA Corporation/Technology Division. April 14, 1981. Call
#4. Some lines have been discontinued. They plan to convert to non-
asbestos in the near future.
42. Production verified by Telecon. Company Representative. Celotex Corp.,
Tamp, Fla., (813) 871-4811, with Anne Duffy, GCA Corporation/Technology
Division, April 13, 1981. Call #3.
43. GAF no longer manufactures asbestos-containing products. Telecon. Harvey
Loud's office, GAF Corp., New York, N.Y., (212) 621-5000, with Anne Duffy,
GCA Corporation/Technology Division, April 13, 1981. Call #1.
79
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44. Telecon. Pat Yoder. Nlcolet Inc., Norristown, Pa., (215) 646-4000,
with Anne Duffy, GCA Corporation/Technology Division, April 14, 1981.
Call #6.
45. Telecon. Company Representative, Quin-T Corp., Tilton, N.H.,
(603) 286-4362, with Nancy Krusell, GCA Corporation/Technology Division,
April 23, 1981.
46. Asbestos Magazine. March 1981.
47. Telecon. Morse, E., Brown Co., Berlin, N.H. , with Syracuse Research
Corporation, July 1979.
48. Anonymous. CPSC Moves to Ban Asbestos Paper. Asbestos, 61(11), p. 14,
May 1980.
49. Telecon. Wong, G., Manning, Paper Co., Green Island, N.Y., with Syracuse
Research Corporation, July 1979.
50. Telecon. Johns-Manville, with Lester Y. Pilcher, GCA Corporation,
March 1980.
51. Asbestos: An Information Resource. R. J. Levine, ed. U.S. Department
of Health, Education, and Welfare, Public Health Service, National
Institutes of Health, DHEW Publication No. (NIH) 79-1681, Bethesda, N.Y.,
May 1978.
52. Meylan, W. M., P. H. Howard, S. S. Lande, and A. Hanchett. Chemical
Market Input/Output Analysis of Selected Chemical Substances to Assess
Sources of Environmental Contamination: Task III. Asbestos.
EPA-560/6-78-005, U.S. Environmental Protection Agency, Washington, D.C.,
August 1978.
53. Daly, A. R., A. J. Zupko, and J. L. Hebb. Technological Feasibility
and Economic Impact of OSHA Proposed Revision to the Asbestos Standard/
(Construction Excluded), Asbestos Information Association/North America,
Washington, D.C., 29 march 1976.
54. Suta, B. E., and R. S. Levine. Non-Occupational Asbestos Emissions and
Exposures. In: Asbestos, Volume 1. Properties, Applications, and
Hazards, L. Michaels and S. S. Chissick, eds., John Wiley & Sons, New
York, N.Y., pp. 171-205, 1979.
55. Cogley, D. Modeling Atmospheric Concentrations in the Vicinity of an
Asbestos Paper Plant. Unpublished. GCA/Technology Division, Bedford,
Mass., September 1979.
56. Bruckman, L., and R. A. Rubino. Monitored Asbestos Concentrations in
Connecticut. J. Air Pollution Control Assoc., 28(12) pp. 1221-1226,
December 1978.
80
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57. Johna-Miinville Corporation, Letter from E. M. Fenner to D. R. Cogley,
July 19, 1979.
58. Telecon. Brunner, B., Customer Service Manager, Chicago Gasket Co.,
1277 West North Avenue, Chicago, 111., (312) 486-3060, with M. Shah,
GCA Corporation, September 1979.
59. Gordon, W. A., and W. G. Riddle. Industry Profile and Background Infor-
mation on Asbestos Cement Products, Millboard and Lumber-Related
Products. U.S. Consumer Product Safety Commission CPSC-C-78-0091, Task 2,
Subtask 2.02, February 1979.
60. Telecon. Hardy, B., Technical Service Specialty Dept., DuPont, Wilming-
ton, Del., (302) 999-3622, with M. Shah, GCA Corporation, September 13,
1979.
61. Fiore, J. V., and R. A. Babineau. Filtration - An Old Process with a
New Look. Food Technology, 33(4):67-72, 1979.
81
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SECTION 5
FRICTION MATERIALS
INTRODUCTION
Friction materials are used in clutches for transmitting torque, in brakes
for slowing or stopping motion, and in torque limiters. Besides their well-
known use in autos, trucks, buses, and railroad cars, friction materials are
also found in other applications where motion must be controlled, ranging
from bulldozers and tractors to typewriters, tape recorders, and parking meters.
Automobile brake linings have used asbestos since 1908 when Herbert Frood
demonstrated that a combination of pure woven asbestos spun on brass wire com-
bined with a specially developed bonding agent resulted in a product with ex-
cellent durability and heat resistance. By the first World War, woven asbestos
brake linings were in common use on passenger cars, commercial vehicles, and
military transports. In 1921, a vulcanized combination of ground-up waste, bonded
asbestos, and a rubber-type binder was used to manufacture the first molded brake
block, but molded blocks were not widely accepted until after the second World
War. Disc brake pads were originally developed for aircraft landing wheel brakes
in 1944 and have become more universally used In the intervening years.
Clutch facings followed a similar pattern of introduction. Impregnated
cotton replaced leather in automotive clutch facings in 1905 and was, in turn,
superseded by asbestos. Today, clutch facings of wire covered with asbestos
yarn are widely used and continued progress is being made in die cast and molded
clutch facings.1
In 1980, an estimated 43,700 metric tons of asbestos, about 12 percent of
the United States fiber consumption, was used in the manufacture of friction
materials.2 Five companies dominate the United States friction material
market, but foreign competition is becoming more of a factor.3
Figures for production volumes were not available but a breakdown of the
estimated value of nsbestos-bearlng friction materials produced in 1979 is
given in Table 19. These data were derived by projecting 1972 figures provided
by Meylan1* to 1979 costs. As shown, brake linings are by far the largest com-
ponent (58.9 percent) of the asbestos friction material Industry. Consequently,
this section emphasizes the production processes and emissions associated with
brake linings, placing lesser emphasis on other products in the friction
materials group.
82
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TABLE 19. VALUE OF ASBESTOS FRICTION MATERIAL SHIPMENTS (IN MILLIONS
OF 1981 DOLLARS)®
Final product
Total product
shipments, including
interplant transfers
1981
1972
Percentage
of
total
(1981)
Brake linings
Woven, containing asbestos
yarn, tape or cloth
Molded, including all non-
woven types
Disc brake pads
Clutch facings
Woven, containing asbestos
yarn, tape or cloth
Molded, including all non-
woven types
Other
$ 27.8 $ 10.2 4.9
308.4 113.1 54.0
38.8 14.2 6.8
54.2 19.9 9.5
132.2 48.5 23.1
9.8 3.6 1.7
Total asbestos friction
material $571.2 $209.5 100.0
Projected from Meylan, et al. (1972), p. 61,** using September 1981
Engineering and Mining Journal cost index factors.
83
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PRODUCT DESCRIPTION
Composition
Many raw materials, including some whose exact roles are regarded as
proprietary information, are used in varying quantities in the manufacture of
friction materials. The major or foundation constituent of practically all
friction materials is asbestos fiber, which can range from 15 to 79 percent
of the final product by weight depending on end use. In 1980, chrysotile
grades 3 through 7 accounted for all of the estimated 43,700 metric tons of
asbestos used to produce friction materials.^ Fiber sizes and types may
be mixed or calcined to improve performance.
Asbestos is used because of its thermal stability, relatively high fric-
tion level, and reinforcing properties, but asbestos alone does not offer all
of the desired properties. Therefore, other materials known as property mod-
ifiers and binders are added. Different types and amounts of modifiers are
used to provide desired levels of effectiveness, wear, fade, recovery, and
noise. Binders hold the disparate materials together. The average composi-
tion of a typical automobile brake lining is shown in Table 20. Individual
product mixes vary considerably from these averages. Manufacturers refuse to
release their exact product compositions due to proprietary considerations but
some details are available in patents. Several examples are given in Table 21.
Table 22 lists binders and property modifiers used in automobile brake
linings. Phenolic-type resins are the most commonly used binders because of
their high binding efficiency and ability to withstand pyrolytic breakdown.
Other resin binding systems are based on elastomers, drying oils, or
combinations.
A wide range of materials are used in friction materials as property
modifiers. In general, property modifiers can be divided into two classes,
nonabrasive modifiers and abrasive modifiers. Nonabrasive friction modifiers
can be classified further as being either high friction or low friction mate-
rial. The most common high friction material is friction dust, a cured res-
inous material derived from cured or polymerized cashew shell liquid, a phenolic
compound. When heated with hardening agents such as hexamethylene tetramine
or formaldehyde, it polymerizes becoming sufficiently hard to be granulated.
Other friction dusts are ditferent combinations of cured resins, polymers,
fillers, and cashew resins. Ground rubber is normally used for noise, wear,
and abrasion control in particle sizes smaller to or slightly coarser than
those of the cashew dusts.14
Low friction nonabrasive modifiers like carbon black, graphite, petroleum,
coke flour, or other carbonaceous material may be added to lower the coefficient
of friction and reduce noise. Normally the materials are added as fine powders
or particles although graphite is occasionally used as coarse particles or
pel lets.4
84
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TABLE 20. AVERAGE BRAKE LINING COMPOSITION
(WEIGHT PERCENT)"
* » *••%. mmarn.-wwmt m. i—funraai * aatrgt,.*. %
Material Automobile Truck
Asbestos 55 33
Resins and polymers 28 48
Oxides and pigments 9 16
Metals 3 2
Carbon, graphite, etc. 5 1
Total 100 100
aLunch, quoted by Meylan,1* et al.
TABLE 21. BRAKE LINING COMPOSITIONS FROM PATENT LITERATURE
(WEIGHT PERCENT) **
Lining No. la
Lining No. 3^
Asbestos
55
Asbestos
35
Barite
10
Barite
2.5
Phenolic resin binder
20
Graphite
7
Brass
5
Brass
13
Magnesium carbonate
8
Phenolic resin
7
Limestone
8
Lead oxide
11.5
Organic calcium powder
10
Buna N rubber
8
Naphtha
7
Copper sulfide
12.5
Methyl ethyl ketone
4
Lining No. 2C
Lining No. 4^
Asbestos
60
Asbestos
50
Phenolic resin
15
Tarry residue
12
Nitrile rubber
3
Barite
20
Cashew dusts
12
Phenolic resin
20
Calcium fluoride
7
Graphite
2
Copper iodide
3
8Sakata, et al., 1974 (Hitachi).
^Keller, 1969 (Abex).
£
Toyota Central Research and Development Labs, 1971.
^Mitchell, 1974 (DuPont)
85
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TABLE 22. PROPERTY MODIFIERS IN FRICTION MATERIALS
Binders
Property modifiers
Use function
Phenolic-type resins
Natural rubber
Buna N rubber
Nitrile rubber
Tire scrap
Pitch
Cork
Gilsonite
Elastomers
Drying oils
Graphite Lower
Coke Lower
Coal Lower
Carbon black Lower
Gilsonite Lower
Friction dusts Lower
Rottenstone (SiOz) Remove decompos
Quartz (Si02) Remove decompos
Wollastonite (CaSi03> Remove
Brass Chips Remove
Zinc and compounds Remove
Aluminum Remove
Limestone (CaC03)
Clays
Silicas
Barite (BaSO^)
Lead and compounds
Antimony compounds Not available
Calcium compounds Not available
Copper and compounds Not available
Barium hydroxide Not available
Potassium dichromate Not available
Magnesium carbonate Not available
Iron oxide Not available
Cryolite (NagAlF3) Not available
Fluorspar (CaF2) Not available
Cardolite Not available
Nickel Not available
Sulfur Not available
friction coefficient and noise
friction coefficient and noise
friction coefficient and noise
friction coefficient and noise
friction coefficient and noise
friction coefficient and noise
tion deposits
tion deposits
decomposition deposits
decomposition deposits
decomposition deposits
decomposition deposits
Improve wear resistance
Improve wear resistance
Improve wear resistance
Improve wear resistance
Lubricant to prevent grabbing
Molybdenum sulfide (M0S2) Lubricant
Calcium fluoride Lubricant
-------
Abrasive modifiers improve brake lining wear resistance at minimus cost
but simultaneously increase noise and decrease mating surface compatibility.
In organic materials such as whiting (ground limestone), barite (baritm sulfate),
clays, silicas, and metals or metal oxides may be added to brake linings in
small amounts and fine particle sizes to provide desired characteristics. For
example, brass chips in heavy-duty friction materials break up undesirable sur-
face films while a small amount of zinc chips can assist in recovering normal
performance following a fade. Particle size Is limited to 100 mesh or finer
because large, hard particles groove and wear mating surface.1*
Clearly, a wide range of components may be present in any automobile or
truck brake lining depending on anticipated application and use patterns. When
¦material variations are combined with manufacturing variations, it is clear
that brake linings can vary greatly from company to company, even when intended
applications are identical. Thus, emissions during production and use can vary
greatly from lining to lining.
Uses and Applications
Friction materials are used wherever motion must be controlled. Friction
materials are used in clutches for transmitting torque, in brakes for slowing
or stopping motion, and in torque limlters. Although use in automobile brakes
is the most important application commercially, asbestos friction materials are
used in buses, trucks, railroad cars, military vehicles, and construction equip-
ment as brakes and clutches. Friction materials are also used in farm tractors,
presses, hoists, forklift trucks, machine tools, shuttle cars, mining equipment,
chain saws, drilling equipment, spinning and knitting equipment. X-ray machines,
tape recorders, typewriters, bicycle brakes, snow blowers, washing machines,
and parking meters.
Special Qualities
All products containing friction materials rely on the coefficient of fric-
tion between mating surfaces to transmit or stop motion. Brakes convert kinetic
energy into heat, absorb the heat, and gradually dissipate it into the atmo-
sphere. Disc brakes consist of two parts, the rotor which is connected to the
wheel and the stator on which the friction material is mounted. Clutches transfer
kinetic energy from a rotating crankshaft to the transmission and wheels. Both
brakes and clutches may operate wet or dry. In dry systems, the heat is con-
ducted to the air and surrounding structure while wet systems operate within
•oil or another fluid which absorbs the heat to maintain temperatures below 200°C
(392°F). The special qualities required by friction materials include:
• Possession of the appropriate coefficient of friction for
the desired application
• Ability to withstand the high temperatures generated at
friction interfaces
• Dimensional stability
• Strength
87
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• Durability
• Lack of abrasive characteristics which could lead to scoring
of mated surfaces
Asbestos is used in friction materials because of the properties listed
in Table 23. The most important properties are thermal stability, reinforcing
abilities*, relatively high friction, fiber flexibility, and relatively low cost.
TABLE 23. UNIQUE PROPERTIES OF ASBESTOS APPLICABLE TO FRICTION MATERIALS3'7
Properties
Comments
Fibrous form
Fine fiber diameter
High tensile strength
Temperature resistance
Flexibility contributes to forming characteristics.
Fibers interlace and interlock, enhancing strength.
Flexibility reduces wear at friction interfaces.
Provide strong reinforcing characteristics because
of the large number of fibers per unit weight.
Provides strength and durability to friction
products.
Chrysotile unaffected by T <200°C (400°F). Stable
for short period of time at T around 1000°C. Able
to withstand high temperatures generated at fric-
tion interfaces, up to 400°C (750°F). The temper-
ature of maximum ignition loss is 1000°C (1800°F).
Cost Provides low cost/performance or cost/physical
property ratio.
SUBSTITUTES
Most large manufacturers of friction materials have active research and
testing programs working toward the development of asbestos-free brakes. In-
centives to change from asbestos to some other material are numerous. Some
new nonasbestos products are at the stage of consumer testing and their manufac-
turers are optimistic regarding their future use. Possible alternatives which
have been considered include:
1. Glass Fiber - Overall strength is lower than that of
asbestos, but strong enough for friction material appli-
cations. Unfortunately, at the temperatures reached by
braking operations, glass fiber melts, even in depths
below the operating surface.
2. Steel Wool - Compared to asbestos, the overall strength is
lower and the cost is much higher.8*9
88
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3.
Mineral Wools - Overall strength is very low and brittle to
the extent of limiting mixing processes.
4. Carbon Fiber - The main properties of carbon fibers are good.
A major consideration is cost which is a great deal higher than
asbestos. It is more efficient than asbestos under high service
temperature conditions, but heat flow is uneven and the tensile
and impact strengths are relatively low. Carbon fiber has high
thermal stability and low density making it especially attractive
for aircraft brakes.8*9
5. Sintered Materials or Cermets - These materials are now being
used to manufacture brake linings for railroad cars and air-
planes. Cermets have extremely high thermal stability. The
wear resistance is not good enough for automobile use and the
cost is too high. Both carbon fibers and cermets are stable
to 7008C (12906F). High thermal conductivity can excessively
heat hydraulic brake fluid causing erratic performance. How-
ever, this problem may be avoided by proper design.10
6. Semlmetallic Materials - Semimetallics are stable to temperatures
of 400°C (750°F) and exhibit excellent wear resistance.
7. Potassium Titanate Fibers - The National Aeronautics and Space
Administration (NASA) has investigated new friction materials
and their applications outside the space program. As part of
this effort an improved friction material for lightweight cars
and trucks was developed which utilized potassium tltanite
fibers with the DuPont trade name FYBEX. However, unfavorable
toxicologlcal effects and other market considerations caused
DuPont to withdraw FYBEX from the market.®
8. AramId Fibers - These are being researched for use in high
performance clutch facings in automatic transmissions. They
do not possess the flexural or physical strength of asbestos,
and the fibers are not easily dispersed as they tend to clump
together.3
9. Vermicullte - Delaminated vermicullte is used in friction
materials which are commercially available throughout Europe.
It maintains strength at high temperatures, is compatible
with phenolic resins, require little attention in manufacturing
methods, and may be used with asbestos to help reduce asbestos
content.11
10. Silicon Nitride - This material was used for the brake pads in
prototypes of the Concorde. It has a longer service life than
asbestos and higher thermal conductivity (desirable in this
application) but is more expensive and heavier than composites
eventually adopted.11
89
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Others - Various other fibers have been used in phenolic binders,
such as aluminosilicates (wollastonite). All have drawbacks and
none are yet as good as asbestos, especially for high-temperature
applications such as disc brake pads.11
Borg Warner Corporation and Abex Corporation (among others) have devel-
oped proprietary substitutes for automobile brake friction materials. Some
are in the consumer testing stage, but no additional information is available
at this time. Raybestos-Manhattan has tested a wide range of materials in an
attempt to find a substitute for asbestos. Fibrous glass, mineral wool,
wollastonite, potassium titanate fibers, heat resistant organic mineral fibers
and natural organic fibers such as cotton and sisal have been considered.
Except for wollastonite and the natural organlcs, the fibers are more expen-
sive than asbestos. Unfortunately, the less expensive fibers lack the heat
resistance and fiber strength needed in brakes. Another problem is that m. ny
of the fibers tend to break up in the milling process and would require some
process modification. Although Raybestos stated publicly in May 1979 that
the company would "halt the manufacture of brake linings and other parts that
contain asbestos"12 by using a blend of 10 to 15 components (40 percent fiber,
20 percent resin binder, and 40 percent friction modifiers), discussions with
company representatives revealed that this was not strictly true.13 The com-
pany has developed some nonasbestos substitute products for certain applica-
tions and has committed itself to a search for nonasbestos substitutes, but
the complete removal of asbestos from all friction materials is not expected
in the foreseeable future.
Cermet or sintered metals, a copper or iron matrix of material reinforced
with steel fiber and various ceramic and metallic property modifiers, are used
primarily In heavy-duty applications where high torque capacities and longer
life are desired. In many applications, cermet products outperform asbestos
products. One example is the aircraft brake market where cermet's market share
continues to grow. Currently, 95 percent of all new commercial aircraft use
cermet brakes. The remaining 5 percent are carbon composite.13
Semimetallic or resin bonded metallic brakes are presently used in heavy-
duty automotive applications such as police cars and taxis. While their per-
formance is supposedly superior to asbestos brake linings, semimetallic brake
linings tend to perform erratically at different temperatures, fade, and pro-
duce more noise than asbestos linings. Currently, semlmetallics are 50 to 60
percent more expensive than asbestos linings but with increased production It
is estimated that costs would drop to within 25 percent of asbestos brake
linings.3 Approximately 20 percent of passenger cars using disc brakes are
equipped with semimetallic disc brakes as original equipment and it Is esti-
mated that in 5 to 10 years, most original equipment disc brakes in passenger
cars and light trucks will be semimetallic.1
General Motors has used a hybrid disc brake consisting of one semimetallic
and one organic asbestos lining in some mass produced passenger cars. The
asbestos lining insulates the brake fluid from heat generated by the semimetal-
lic surface during braking, but never actually touches the motor surface. In
effect, the asbestos content of the brakes is reduced. Compared to asbestos-
lined disc brakes, the hybrid brakes have a higher coefficient of friction,
90
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higher heat resistance, and wear longer but are more noisy and more expensive.
While some industry sources feel that hybrid disc brakes will capture the
market because of superior performance, others believe that trends to lower
speed limits and lighter weight cars will reduce the need for high performance
brakes.9
The friction material in disc brakes is formed into an intrinsically
stronger shape than in drum brakes and consequently needs less fibrous rein-
forcement. Asbestos is used In many disc brakes to reduce thermal shrinkage
and withstand thermal shock, but asbestos-free semimetallic disc brakes have
been developed for automotive uses. A typical composition is given in
Table 24.
TABLE 24. COMPOSITION OF AN ASBESTOS-
FREE DISC BRAKE PAD (IN
VOLUME PERCENT)U
Carbon
45
Iron powder
25
Steel fiber
10
Phenolic resin
20
Semimetallic disc brakes, originally designed and produced by Bendix
Corporation and now also manufactured by two other companies, are expected to
increase their market share relative to asbestos disc brakes. In fact, it is
projected that in 5 years nearly all original equipment disc brakes made for
passenger cars and light trucks will be made with semimetallies. American
automobile manufacturers have targeted 1983 as the last model year asbestos
disc brakes will be used.1**
As for drum brake linings, a nonasbestos product for passenger cars is
not available commercially at this time. However, intense research in this
area is underway, with specifics still proprietary at this time. The first
commercially available nonasbestos drum lining may contain some combination
of steel fibers, synthetics, cotton, ceramic, carbon, natural materials,
glass, and mineral fibers. For model year 1980, commercial nonasbestos lining
was not available for drum brakes; however, Bendix Corporation is apparently
very close to marketing this kind of product. American automobile manufacturers
have targeted 1985 as the last model year asbestos drum brakes will be installed
as original equipment.
The use of cermet brake linings may increase once the problem of their
interaction with hydraulic brake fluid can be solved. With all of the current
research into brake lining substitutes, a nonasbestos product for more univer-
sal use should become available in the future.
91
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MANUFACTURING
Primary Manufacture
Plants manufacturing friction products contain a diverse collection of
machinery. Typically included are grinders, mixing vats, mills, molds, ex-
truders, curing ovens, lathes, metal stampers, presses, paper machines, con-
veyors, and drill presses. Chemical operations, such as preparation of spe-
cific resins, may also be performed onsite. The exact mix of machinery at any
given plant depends upon the manufacturing processes in use. Friction mate-
rials can be molded using either a dry mix or a wet mix process, woven like
textiles, or formed like papers.
Overview of Manufacturing Process—
In the first steps of manufacturing friction materials, bags of asbestos
are typically dumped into mixers that blend the formulations in either a wet
or dry state depending on product specifications. A fluffing device may also
be used. Next, the mix is fed through a compression molder (dry) or an ex-
truder (wet), to form strips that are cut and bent into various widths and
lengths. A release compound is added to prevent sticking. Dry-mixed formu-
lations, which include a small amount of solvent, are transferred to pressing
molds where slabs are formed, sometimes after a preheating step. Slabs are
then hot pressed, causing resin in the slabs to flow, binding the mixture upon
curing. The slabs are sawed into specific parts and sent to a curing oven.
Dry Mix Molding Process—
The steps typically employed in manufacturing friction materials using
the dry-mix molding process are shown in Figure 6. Asbestos fibers, metallic
constituents, bonding agents, and other additives are weighed, mixed, then
placed into a metal mold and formed into a uniform sheet using a preforming
press. The mold is removed and the material is heated sufficiently in a cur-
ing press to allow the resin to flow and set. Only partial curing occurs during
this step. The material is then cut to product-sized segments and rough ground.
The resin is then softened by a preheating step after which the proper arc is
formed by steam-heated bending. In the final curing step, the segments are
placed In compression molds (lunnettes) and baked at a pressure of 1,000 to
2,000 psi. This converts the resin to a permanent thermoset bond so that the
desired arc will be retained. Finishing steps, including sanding and grind-
ing to the correct thickness, edge grinding, drilling holes for rivets, in-
specting and branding are required before the brake linings can be packaged.
Wet Mix Molding Process—
Figure 7 shows the major steps in the manufacture of wet-mix molded
brake linings. The term "wet mix" is actually a misnomer since the ingredients
of the molded lining are relatively dry. The term arises from the use of a wet
solvent in the process.
The raw materials are blended in the proper proportions, mixed and then
sent through a hammer mill in order to ensure homogeneity. The mixture is
then forced into the nip of two roll formers where it is compressed or ex-
truded into one continuous strip of friction material. A chopper cuts the
material to the proper length after which an arc former is used to give the
92
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I
RAW ASBESTOS FIBER
MOLD
MOID REMOVED
CURING PRESS
ROUGH GRINDING
STEAM
CONDENSATE
COOLING
WATER
STEAM
CONDENSATE
COOLING
WATER
WATER
BAKING OVEN
FINISHING OPERATIONS
PACKAGING
PERFORMING PRESS(h)
RECEIVING AND STORAGE
DRY MIXER(H)
RADIUS GRINDING(H)
DRILLING
COUNTERBORING(H)
CLAMPING INTO
LUNNETTES
STRIPS CUT
TO LENGTH(H)
BLEND OF ASBESTOS AND (H)
OTHER RAW MATERIALS
SHEET CUT
INTO STRIPS(H)
COOLING
WATER
STEAM PREHEAT
STEAM-HEATED
BENDING
Note: (H) - Indicates hooded
operat Lotis.
Figure 6. Dry-mixed molded brake lining manufacture.15
-------
I
RAW ASBESTOS FIBER
SOLVENT,
SOLVENT
RECOVERY
SOLVENT,
HIGH-SHEAR MlXER(H)
RACKING
HAMMER MILL(H)
chopper(h)
TWO-ROLL MILL(H)
PACKAGING
ARC FORMER
BAKING OVEN
BLENDING OF ASBESTOS
AND OTHER RAW MATERIALS
FINISHING
OPERAT IONS(H)
FORCED AIR
DRYING CHAMBER
RECEIVING
AND
STORAGE
CONSUMER
Nott-: 01) - Indicates hooded
operations.
Figure 7. Wet-mixed molded brake lining manufacture.15
94
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material the desired brake lining shape. The linings are placed in racks,
air dried and baked to remove any remaining solvent before final finishing
operations.
In an alternative process, arc-formed linings are placed in metal molds
and baked in an oven prior to finishing and inspection. Another variation has
automatically measured volumes of the raw material mixture dropped into disc
brake molds where pressure is applied, shaping the contents which are removed
and baked after finishing.
Molded Clutch Facings—
Molded clutch facings are produced in a similar manner, as Figure 8 il-
lustrates, Asbestos fiber, a rubber friction compound and a solvent are com-
bined In a mixer and then conveyed through a two-rolled mill which compresses
the mixture into a continuous strip of material. A punch press is used to cut
the material into doughnut-shaped pieces. Scraps from this process are mixed
and then fed back into the two-roll mill while punched sheets are racked,
placed in drying ovens and then into baking ovens for final curing and solvent
extraction. Oven dried sheets are finished, inspected and packaged. Finish-
ing operations include sanding, edge grinding, drilling and dusting.
Paper Products—
Some friction materials can be classified as paper products based on
their method of manufacture. In particular, discs for automatic automotive
transmissions are punched from rolls of asbestos paper formed on a Fourdrinier
or cylinder machine. The forming process is discussed in detail in Section 4,
Asbestos Paper Products. Since transmission discs are annular, much of the
paper produced becomes scrap. About 70 percent of a roll is wasted in cutting
and must be recycled. In a later step the paper discs are sprayed with a
phenolic resin, heated, and bonded to steel wafers. The product transmission
plates, steel cores with friction material on either side, are then ground,
inspected, and packaged.
Die Cast Clutch Facings—
Larger clutch facings are frequently die cast. Raw materials which in-
clude asbestos and perhaps rubber and metallic oxides impregnated with resin
are mixed, then brought to the work station. A worker measures out the neces-
sary amount and pours it into a mold where it is pressed to the required
density. After drying, the form is gear cut and bonded to a metal backing.
The face is then ground with a pattern designed specifically for the eventual
product application.
Woven Products—
Woven clutch facings are frequently classified as being asbestos friction
products. Figure 9 shows the press used in their manufacture. More detail on
woven products is available in Section 12, Textiles.
Woven clutch facings and brake linings are manufactured from high strength
asbestos fabric that may be reinforced with wire. The fabric is predrled in an
oven or by autoclave before being impregnated with resin in one of several
95
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RAW ASBESTOS FIBER
PUNCH PRESS
SANDING (H)
INSPECTION
RECYCLE (H)
MIXER
BAKING OVEN
DUSTING
BRANDING (H)
PACKAGING
DRYING OVEN
TWO-ROLL MILL
RACKING
HIGH-SHEAR MIXER (H)
EDGE GRINDING (H)
DRILLING
COUNTER BORING (H)
RECf IV INC. AND
STORAGE
BLENDING OF ASBESTOS (H)
AND OTHER RAW MATERIALS
Note: (H) - Indicates CONSUMER
liooded operations.
Figure 8. Molded clutch facing manufacture.15
96
-------
STEAM
CONDENSATE
COOLING
COOLING
WATER
WATER
CONDENSATE^
COOLING ^
STEAM
COOLING
WATER
WATER
BAKING OVEN
PACKING
FORCED-AIR COOLING
FINISHING (H)
PREFORM WINDING
PRECURING PRESS
SLITTING TO TAPES (H)
STACKING
ON METAL PLATES
WIRE-REINFORCED
CLOTH ROLLS
HOT PRESSES
FRICTION COMPOUND
BATH
CONSUMER
Note: (H) - Indicates hooded
operations.
Figure 9. Woven clutch facing manufacture.15
97
-------
techniques. The fabric may be immersed in a resin bath, exposed to the binder
in a pressurized autoclave, mixed with resin before being wound into yarn or
pressed beneath a roll whose surface is covered with resin. Once solvents are
evaporated from the fabric, it is made into brake linings or clutch facings.
Brake linings are made in a manner similar to that described earlier:
woven clutch facings are made differently. Treated fabric is cut into tape
width strips by a slitting machine before being wound around a mandrel to form
a fabric roll. The roll is placed in a steam-heated press, baked in an oven
to cure the resin in the clutch facing, then finished, inspected and packaged
in the by now familiar sequence.
Secondary Manufacture
Some brake pads are sold to secondary manufacturers. The division between
primary and secondary manufacturers, however, is not particularly important since
secondary manufacturers perform a subset of the tasks generally considered the
preserve of primary manufacturers. Secondary manufacturers take brake pads,
rivet or bond them to brake shoes, inspect them, and package them as the final
product. Any defective assembly could discredit their properly built products.
Manufacturing Plants and Production Volumes
The manufacture of friction products is highly labor intensive, with many
processing and handling steps. Because of the labor intensive production pro-
cess, differences between large and small manufacturers are limited to the
variety of products formed and the number of work stations devoted to each.
There are presently a large number of friction material manufacturers but many
of the smaller firms have extremely limited product lines.
Table 25 lists the U.S. manufacturers of asbestos-bearing friction mate-
rials including, if known, their respective friction product sales in 1975 and
the products they manufacture. Both larger diversified companies such as
Raybestos-Manhattan and smaller, single plant companies are included in this
list. The first eight companies listed on this table accounted for 75 to 85
percent of the total estimated sales of asbestos friction products in 1975,
a pattern consistent with the industry's historical trends. From 1954 to
1967, the eight largest companies together accounted for 86 to 91 percent of
the industry's value of shipments.'*
ASBESTOS RELEASE
For friction materials, release of asbestos fibers will be discussed for
four general areas: during manufacture, use, replacement, and disposal.
Under manufacture emissions is included workplace concentrations, for various
areas, human exposure to airborne asbestos, water emissions, and solid waste.
Replacement emissions discuss release as a part of the automotive aftermarket
which includes refacing and rebuilding, repackaging and general repairs.
Disposal emissions are included within the manufacturing emissions sections
(i.e., solid waste, etc.). An input/output figure is shown first to help
detail the path of these emissions.
98
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TABLE 25. U.S. MANUFACTURERS OF ASBESTOS-BEARING FRICTION MATERIALS9,X6-37,5S
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Figure 10 hIiows est lmnt t*s of firoet'HB nnd iIInpoKnl omlshinns for the*
aubi'«Li)u Irictlon niulurlaLs Industry. These figures .ire based on Lev lac 1 ^ ^
1974 estimates projected to 1980 U.S. Bureau of Mines consumption figures.
Potential sources of emissions include blending mixing, cutting, milling,
chopping and finishing operations. Of the 43,700 metric tons of raw asbestos
fiber processed in 1980, approximately 42,525 m.t. are incorporated into the
product and 1111.9 m.t. are sent to disposal as vacuum cleaner and baghouse
dust. An estimated 10.9 metric tons escape through a control device (typically
a baghouse). Levin's^® atmospheric emissions estimates are based on gross
assumptions with a reported uncertainty of at least an order of magnitude.
Meylan's^ estimates of emissions are generally 1 to 3 orders of magnitude
leas. Atmospheric emissions from disposal, based on GCA estimates, are shown
to total 2.2 metric tons per year for the friction materials industry. This
last estimate, which follows Levine's^ 1974 data, also takes into account the
Asbestos NESHAPS regulations adopted in 1975 regarding the disposal of
asbestos-containing waste material.
During Manufacture
Workplace Fiber Concentrations—
Table 26 shows the time-weighted average exposures at different points In
the friction material production process. These figures are based on 12 planes
which consumed approximately 35,000 m.t. of asbestos in 1975 and made up about
60 percent of the friction products segment during that year. Data was ob-
tained by Weston39 in a survey using industry questionnaires and is of question-
able validity as industries may tend to report biased figures. In addition,
the range of data reported is extremely broad, indicating questionable sampling
and counting procedures.
TABLE 26. TIME-WEIGHTED AVERAGE FIBER CONCENTRATIONS OF OPTICAL
MICROSCOPE VISIBLE FIBERS GREATER THAN 5 pm IN FRIC-
TION PRODUCTS MANUFACTURING PLANTS39
Fiber count
Range
Typical
Process step
(fiber/cc)
(fibers/cc)
Receiving and storage
0.25
- 2.5
1.0
Fiber introduction
0.4
- 4.6
2.5
Mixing
0.2
- 8.0
2.3
Forming and rolling
0.5
- 22.0
3.3
Curing
0.5
- 3.5
1.5
Finishing
0.6
- 7.4
2.0
Adjustment and printing
0.7
- 1.0
1.0
Inspection
0.1
- 15.0
2.0
Packaging
1.0
- 2.0
1.5
*Based on plants representing 50 percent of asbestos friction
material production.
100
-------
MANUFACTURING OPERATIONS
SLEW) INC
FINISHING
*2.575 TPY
LEGEND
C ^ inpwvoutput
CD
HANUfACTUHINC
processes
SCRAPS
AND REJECTEO
PAOOVCT
CONTROL EQUIPMENT
ULTIMATE DEPOSITION
SOLID
WATER
AIR
DISPOSAL
EH ISS IONS
2.2 TPT
Figure 10. Input/output estimates for the asbestos friction materials industry in metric tons.
-------
A review of the data collected Indicates that in addition to variations
in sampling and counting procedures there are many reasons for the wide vari-
ations in the range of fiber counts. The largely individual manual techniques
and worker practices introduce considerable deviations, as does the percentage
of asbestos in the product which may range from 30 to 70 percent by weight.
Receiving and storage—Exposures during receiving and storage in asbestos
friction material production are identical to receiving and storage exposures
in all other primary asbestos industry segments. Consequently, the range re-
ported for asbestos paper, 0.25 to 2.5 fibers/cc TWA and the3^ypical value,
1.0 fibers/cc TWA, are equally valid for friction materials.
Fiber introduction—Bags of the raw material may be manually opened and
dumped into hoppers for transport to mixers. Fiber levels during this opera-
tion are higher than thoae in papermaking fiber introduction, ranging from 0.4
to 4.6 fibers/cc TWA for friction materials as opposed to a 0.3 to 2.8 fibers/
cc TWA range for papermaking. Typical fiber levels exhibit a similar differ-
ence, with 2.5 fibers/cc typical of fiber introduction for friction products
rind 1.9 fibers/cc typical for papermaking.89
It is not clear why such a difference should exist, since the processing
step is similar. Perhaps the fact that in some paper applications it is not
necessary to dump the fiber out of a bag contributes to lower typical values
in papermaking. However, this characteristic should not affect the range re-
ported since some paper applications require that the asbestos be removed from
the bag.
Mixing—The combined raw materials may be mixed either dry or wet, depend-
ing on product specifications. The state in which mixing occurs greatly in-
fluences the workplace fiber levels, since fibers in water are unlikely to
become airborne, while dry fibers can easily be dispersed. Fiber levels of
0.2 to 8.0 fibers/cc TWA were reported with 2.5 fibers/cc TWA considered to
be typical.3*
Forming or rolling—The product of the mixing stage is fed to a com-
pression molder or an extruder, again depending on the required product.
Levels of 0.5 to 22.0 fibers/cc TWA were recorded; a level of 3.3 fibers/cc
TWA was considered typical.39 The higher exposure levels are caused by the
manual handling of the dry preform mix, which is conveyed in open carts,
scooped bv hand, weighed, and ooured Into a block mold where it is mechani-
cally pressed Into the shape of the finished product.38
Cur lug—Sumo lomulae require a heating step that causes resins to flow
and bind the mixture. In the curing step fiber levels ranged from 0.5 to 3.5
fibers/cc TWA. A fiber count of 1.5 fibers/cc TWA was typical.39
Finishing—Parts taken out of the curing oven undergo a number of steps
to produce the final product. These machine-assisted manual finishing steps
may include grinding, sawing, drilling, blanking, tapping, and boring. Fiber
levels in finishing were typically 2.0 fibers/cc TWA, although reported values
ranged from 0.6 to 7.4 fibers/cc TWA.39
102
-------
Adjustment and printing—After finishing, the friction products are dusted,
adjusted, and printed. Fiber levels in this operation are consistently close
to 1.0 fibers/cc TWA. The rang<< of exposures during this process In vury
narrow, 0.7 to 1.0 libers/cc TWA."
Inspection—Generally considered to be an examination of the finished prod-
uct, inspection encompasses different activities in different plants. Some
plant inspection stations only examine the finished product; if the product is
defective or needs more comprehensive finishing it is returned to the finishing
area or rejected entirely. Other plants have additional equipment In the
inspection area so that any defect in the product can be rectified immediately.
Consequently, fiber counts recorded in inspection areas vary widely from 0.1
to 15.0 fibers/cc. Usually, the fiber level will be toward the low end of the
range, with 2.0 flbers/cc TWA considered typical.39
Packaging—Even workers involved in packaging the final product are ex-
posed to fibers. The range of reported fiber levels in packaging was 1.0 to
2.0 fibers/cc TWA with 1.5 fibers/cc TWA considered typical.
Emissions to Air—
The maximum allowable exposure over a AO hour week for workers in the
asbestos industries has been set at 2 f/cc.* Workers are exposed to an average
fiber count of 1.9 f/cc,* with fiber counts as high as 22 f/cc* being reported
(see Table 26). The values reported reflect levels recorded in or before 1975
and are probably higher than present day concentrations. With greater worker
awareness and increased employer concern, along with the regulatory activities
of 0SHA, it Is very likely that friction product worker exposure concentrations
are well below the 2 fiber/cc limit. Documentation in the open literature to
substantiate this belief, however, is not available.
With a workplace; fiber count of 1.9 f/cc, workers can be expected to
inhale 119+ billion libers per year.1,0 Estimates of nonoccupational ex-
posure to asbestos have been made using a binormal continuous plume dispersion
model with assumed plant emissions. The affected population was assumed to be
those people living within a 5 km radius of a friction material manufacturing
plant. The atmospheric asbestos concentration around the plant was estimated
to be 23,000 f/n»3+ and the annual amount of asbestos Inhaled was estimated to
be 125 million fibers* per person. This compares to a mean ambient urban
exposure of 5,000 fiber s/m^ with an average annual inhalation of 27.4 million
fibers per person.ka
Release to Water—
Water is not used directly In the production of friction materials except
for those products formed on paper machines from a 2 to 3 percent solids
slurry. Water usage and consequent water pollution associated with this pro-
cess is discussed in Section 4, Asbestos Paper Products. Despite the term
Optical-microacope-visible fibers >5 ym in length.
•f
Electron-microscope-visible fibers.
103
-------
"wet mix" used in the description of one of the manufacturing processes it is
actually dry because no wastewater is generated. Solvents are used to make
the mix of raw materials more pliable; no excess water is used and no floor
drains are present.
Wastewater is generated in some solvent recovery operations and in wet
dust collection equipment used to control dust throughout the plant. Solvent
recovery wastes normally have very low suspended solid levels. A typical sol-
vent recovery operation has been reported to have 0 mg/1 suspended solids in
its waste stream.1,1 Wastes from wet dust collection have significantly higher
solids concentrations.
Wastewaters from wet dust collectors are slurries of dust from plant opera-
tions, and are characterized principally in terms of suspended solids. Clearly,
the concentration will be a function of the amount of dust generated and the
water flow rate which can vary from 1.9 to 37.9 liters per minute per 28.3
standard cubic meters of air per minute. Plant air systems served by wet scrub-
bers range from 283 to 7079 scam, resulting in discharges of 189,250 to
2,838,750 liters per day.1,1 Units are for the most part equipped for partial
recirculation. Sludge, or settled slurry is discharged to a settling lagoon
where it becomes a solid waste problem. In a typical plant using wet collec-
tion, about 1566 kg of asbestos are collected annually. About 95 percent or
1488 kg are removed as sludge by clarification. The sludge Is disposed of by
landfllling while the remaining 78 kg of asbestos are discharged to surface
waters.k
Release to Land—
Most of the solid waste generated in the manufacture of friction material
is produced in grinding. In the past, grinding dust was collected for use as
solid fill in marshlands and low-lying areas. It is now trucked to sanitary
landfills for disposal but as the hazards of asbestos have become better known,
fewer and fewer landfills are willing to accept asbestos-containing materials
for disposal.
Estimates of the percentage of asbestos lost in grinding and drilling range
from 12.7 percent to 30 percent,"12 but even with the high cost of raw mate-
rials, asbestos in these scraps is not recovered for reuse. Once the binders
and resins have set, it is uneconomical to break them down to salvage the fibers.
In most cased baghouses are used to collect grinding and drilling dusts.
It has been estimated that wastes can amount to as much as 12.2 tons/month
for a plant producing 40,000 brake shoes per day.* Based upon a total asbes-
tos consumption of friction materials of metric tons in 1980, 1,112 tons of
asbestos would be lost in product waste. Baghouses would collect about three-
fourths of this total, or about 834 tons, while the remainder, 278 tons, would
be collected by vacuum cleaners and as damaged product.1*
During Uhc
During vehicle operation friction material, whether used as a disc pad,
drum lining or clutch facing, engages with a metal rotor to form a sliding
friction couple which converts the kinetic energy of rotating members into
heat, absorbs heat and dissipates it to the surroundings. Emissions are gener-
ated by wear. Asbestos fibers are pulverized into small particles which are
104
-------
either trapped in the brake or clutch housing, fall to the road or an.- emitted
to the atmosphere. Moat of the anbestos, however, is heated sufficiently to
caiiue chemical convention to olivine or I'orsterito.
A number of articles have discussed asbestos emissions from brake linings.
Table 27 summarized the published data. A detailed discussion of the reported
information is provided in reference 4.
Jacko and DuCharme reported1*2 that approximately 33.6 million kilograms of
asbestos in friction material wear away annually. Based on their experimental
finding that only about 0.2 percent of the debris is not converted to some
other substance, total annual asbestos emissions were estimated to be 71,759
kilograms. Of this amount, 85.6 percent or 61,426 kilograms were estimated to
drop out on to the ground, 11.2 percent or 8,037 kilograms was estimated to be
retained within the brake or clutch housing and only 3.2 percent or 2,296
kilograms was believed to become airborne.
Rohl, et al.*3 performed a similar calculation based on a separate anal-
ysis of friction material wear debris, but otherwise retaining all of Jacko
and DuCharme's assumptions. Their best estimates of the total annual asbestos
emission were that 1,329,039 kilograms of asbestos dropped out, 172,367 kilo-
grams were retained in brake and clutch housings, and 49,896 kilograms become
airborne.
Elevated levels of asbestos were found in a study by Bruckman and Rubino'2
in which airborne asbestos concentrations were monitored at three Connecticut
toll plazas. Asbestos concentrations were found to vary between 3 ng/m3 and
41 ng/m3. A nearby large industrial asbestos user was suspected of influencing
the highest measured concentration. Although no correlation was made between
vehicular traffic and the asbestos concentration it was concluded that the
decomposition of brake linings is a significant source of airborne asbestos
fibers.
During Disposal
Friction materials are usually replaced before they are completely worn
out. Most passenger vehicles reportedly use a set of asbestos-containing brake
linings every three to four years.53 Asbestos-containing friction products
are disposed of in the form of worn brake linings, disc pads( and clutch
facings. These materials may be discarded as scrap pieces separated from any
metal component which can be reused or scrapped along with the machinery they
were a part of such as automobiles.
Because of the means by which they are manufactured, asbestos fibers are
bound within the pieces even though they are worn. During disposal, asbestos
material should not be released from the worn pieces due to the lack of
sufficient energy to dislodge the fibers bound in the friction material
matrix. Ultimately, the nonfriable friction material is either incinerated or
landf11led.
105
-------
TABLE 27. SUMMARY OF PUBLISHED DATA - ASBESTOS EMISSIONS FROM BRAKE LINING USE*2*48
Publication
source
Method used Co collect
¦Isslon or debris saaples
Method used
to determine
asbestos content
of ealssion
aebrt» saaples
Asbestos
particle site
distribution
\sb**tcs content ci
emission or debris
O
&
Lynch. 1%8,J
Hatch, 1970*
Uicklab and Knight,
1970
Bushet al., 1972*
ArwJeracm et •!.» 1973
Jacko and DuCharme,1'1
1973 (contains
jw data as
Jacko «t al., 1973)
Laboratory siaulations utilizing brake-teat ing
ra chines or dynaaooeters. Saaples collected
on 0.8 - pore site membrane filters.
A dust cloud was generated by using coapreased
air Jets to reaove Just from brake lining*
in an auto repair garage. Saaples were
collected by aeaos of a hand pvap located In
center of dust cloud.
Samples vere collected directly from debris
remaining as brake dust and from membrane
filters exposed during brake cleaning
operations utilizing coapressed air.
Filter pore slxe is not given.
Laboratory simulations utilizing a disc brake
asaeably mounted on an inertial dynsteoaeter.
Samples were collected on suitable filter
paper.
laboratory slaulatlons utilising a disc brake
asseably counted on a dynaa»aeter. Air samples
of vear debris collected down wind of disc
brake.
Samples vere generated by operating a standard
Areeriean car under typical driving condition*
in Detroit. Michigan. More abusive conditions,
such as face tests, were also included. Brake
and clutcb assemblies were enclosed by spe-
cially designed collectors. Samples were
collected frost (1) dropouts during use,
(2) dust retained in llnlny, nasanblies, and
(3) airborne saaples collected on aeabrane
filters.
Electron micrographs Not discussed
Not »t .u *d
Hot stated
Neutron activation
Iransaisalon electron
rlcroscnpy
Optical and electron
microscopy
a4" of fibers
fell in 2-5 ~m
length category.
Only 6! were
longer than 5 -t
Not discussed
Not discussed
teat results and
and procedure*
precluded a hize
distribution
estiaate
301 of fibers
were fron
0.25-0.50
in length; 60*
were longer
than 0.5 »in
<1*, exec! under severe-strest
conditions
~r
1.6! and Us»
—44! (this figure is not
accurate; see discussion)
-0.021
0.25Z overall average (an
Independent check done by
BatelJe Labs give a figure
of 0.171->
(continued)
-------
TABLE 27 (continued)
Publication
source
Method used to collect
eaisslon or debris saaples
Method used
to determine
asbestos content
of mission
debris saaples
Asbestos
particle size
distribution
Asbestos content of
emission or debris
Kohl et al.. 1976
Ten saaples of sutoaobile brake drtai dusts were
collected frota aalntenance shops In the New
York area.
X-ray dlffractoaetry
transalaslan electron
¦icroscopy, selected
area electron dif-
fraction, and elec-
tron microprobe
analyses
2-lSS; average of 3-61
SOS of fibers Consistent with, but lowar than,
vsrs shorter quantitative determination sade
than 0.4 us by X-ray dlffractonatrv; no
length percentages are given
, . Alste et al., 1976*
O
>4
Rohl et al., 1977*1
Samples were taken from fresh and worn brake
linings and froa the ataosphere near a freeway.
This ia basically a reprint of the Rohl et al.,
1976 study with the Inclusion of brake wear
test saaples obtained froa Europe and Australia.
Electron "icroscopy
Majority were
<2 ua In saxlaua
linear dimension
Mo percent figure given, however,
conclusion was tbst aajor effect
of braking appears to be in
separating bunches of fibers and
reducing their average length,
but not in altering their crystal
structure
The sean weight percentage rangeJ
froa 1.4X in Australia to 2.5t in
France
-------
Emlaaluns In Automotive Afte rmarket
The automotive aftermarket in which asbestos exposures may occur is
divided into three major sections: refacing or rebuilding of friction
materials, repackaging of friction materials, and general brake repair and
service.39
Refacing and Rebuilding—
The major difference between refacing operations and plants in the primary
friction materials segments is that no raw asbestos fiber is handled in the
smaller rebuilding plants. Therefore, the control problems are not as acute.
Most rebuilt asbestos-bearing parts plants have had local controls for a long
time. Asbestos exposure levels measured at three of these establishments were
reported by NIOSH during the American Industrial Hygiene Conference in New
Orleans in May 1977 and are presented by process step In Table 28.
Repackaging—
Repackaging operations in the automotive aftermarket consist of manually
transferring asbestos friction material products from one container to another
at a location other than the facility where the friction material was produced.
Asbestos exposures for this sector have been reported to range from 0.2 to 0.6
fibers/cc TWA.*
General Repairs—
From the existing data on asbestos exposure levels during brake repair
work, it appears that an establishment using compressed air for blowing resi-
dual dust from brake lining assemblies may exceed the 10.0 fibers/cc ceiling
limit under the current OSHA standard. Data reported by Rohl'*9 on asbestos
emissions during brake lining maintenance Indicated that a peak exposure of
29.8 fibers/cc had been encountered 0.9 to 1.5 meters from the workplace.
These data are presented in Table 29.
108
-------
TABLE 28. ASBESTOS FIBER3 EXPOSURE LEVELS IN REBUILDING BRAKE
AND CLUTCH ASSEMBLIES 5 **
Fibers/cc TWA
Facility Receiving and Bonding and Cutting and Inspection and
cleaning riveting grinding packaging
Mean
Range
Number of
samples
Mean
Range
Number of
samples
1.1
0.4 - 4.8
15
4.0
1.0 - 7.6
5
0.6
0.2 - 1.4
20
2.7
1.1 - 5.8
6
1.1
0.8 - 1.6
6
5.0
1.5 - 9.3
6
0.7
0.8 - 1.1
4
C
Mean 1.3 0.8
Range 1.2-1.3 - 1.5-9.3
Number of 2 6
samples
a
Fibers 5 to 100 vim were counted using phase contrast microscopy
according to the NIOSH method.
TABLE 29. FIBER LEVELSa DURING BRAKE
LINING MAINTENANCE*9
Distance from _ .
workplace Peak exposure
(meters) (fibers/cc)
0.9 to 1.5 6.6 to 29.8
1.5 to 3.05 2.0 to 4.2
3.05 to 6.1 0.4 to 4.8
Background samples 0.1 to 0.8
aFibers 5 to 100 ym were counted using
phase contrast microscopy.
109
-------
CONCLUSION
Between 1978 and 1980 there has been a 41 percent decline in the amount
of asbestos consumed to manufacture friction products. The decline can be
attributed to a slowdown in automobile sales and the increasing use of
asbestos substitutes* Atmospheric release of asbestos fibers during primary
manufacturing, by far the largest source of emissions in this category, is
estimated to have declined co 13.1 tons per year in 1980 from 21.6 tons per
year in 1978. Asbestos containing solid waste is estimated to have declined
from 1,876 tons to 1,112 tons between 1978 and 1980. Process wastewater
discharged from friction products manufacturing plants Is not expected to be
laden with asbestos fibers. Wastewater from wet dust collectors employed to
control fiber release, however, will contain asbestos material. About 95
percent of the asbestos material suspended in the control device wastewater is
removed as sludge by clarification. The sludge is typically disposed of by
landfllllng with the remaining five percent discharged to surface waters. The
decline in asbestos releases that has been estimated between 1978 and 1980 is
expected to continue through 1981, coinciding with the turndown in the economy
and an increased interest in asbestos substitutes.
Beyond 1981, the outlook for the use of asbestos in friction materials is,
at best, mixed. The majority of the industry's products are used in passenger
automobiles and, as such, are influenced by the vagaries of the buying public.
If a lot of new cars are being sold, a lot of new brakes will be required.
Conversely, if fewer new cars are sold, more used cars in the marketplace will
result in more sales of replacement brakes. Further uncertainty is introduced
by the American automobile manufacturers' avowed intentions to eliminate
asbestos from original equipment brakes by the 1985 model year. If a success-
ful substitute is found, asbestos consumption in friction materials will drop
precipitously.
110
-------
1
2
3
4
5
6
7
8
9
10
11
12
REFERENCES
Bradfield, R.E.N. Asbestos: Review of Uses, Health Effects, Measure-
ment and Control. Atkins Research and Development, Epsom Surry,
England. January 1977.
Clifton, R.A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of Mines.
Washington, D.C.
Wright, M.D., et al. Asbestos Dust Technological Feasibility Assessment
and Economic Impact Analysis of the Proposed Federal Occupational
Standard: Part I. U.S. Department of Labor, OSHA. September 1978.
(Draft).
Meylan, W.M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination:
Task III - Asbestos. EPA 560/6-78-005. August 1978.
Bark, L.S., D. Moran, and S.J. Percival. Chemical Changes in Asbestos-
Based Friction Materials During Performance. A Review. Wear. 34:131-139.
1975.
Zussman, J. The Mineralogy of Asbestos. In: Asbestos, Volume 1, Pro-
perties, Applications and Hazards. L. Michaels and S. S. Chissick, eds.
John Wiley and Sons, New York, N.Y. 1979. pp. 45-65.
Hodgson, A.A. Chemistry and Physics of Asbestos. In: Asbestos, Volume
1, Properties, Applications and Hazards. L. Michaels and S. S. Chissick,
eds. John Wiley and Sons, New York, N.Y. 1979. pp. 67-114.
Jacko, M.G. and S.K. Rhee. Brake Linings and Clutch Facings. Encyclo-
pedia of Chemical Technology. Third Edition, Volume 4. John Wiley &
Sons, New York, N.Y. 1979. pp. 202-212.
Telecon. Reginal D. Kelley, Force Control Industries, with Robert
Bouchard, CCA Corporation. March 3, 1980.
Green, A.K., and A.M. Pye. Asbestos Characteristics, Applications and
Alternatives. Fulmer Research Institute, Fulmer Special Report No. 5,
ISSN 0427-7457. 1976.
Pye, A.M. A Review of Asbestos Substitute Materials in Industrial
Applications. Journal of Hazardous Materials (Netherlands).
3:137-138. 1979.
Einhaus, J.R. Age of Asbestos on Vehicle Parts Ending. Automobile
Industries, p. 27-31. May 1979.
Ill
-------
13.
14.
15.
16.
17
18
19
20
21
22
23
24
25
26
27
Telecon. M. G. Jacko, Bendix Materials Center, with Nancy Roy, GCA Corpora-
tion. November 19, 1979.
Telecon. M. G. Jacko, Bendix Materials Center, with Nancy Roy, GCA Corpora-
tion. August 1979.
U.S. Environmental Protection Agency. Control Techniques for Asbestos
Air Pollutants. Publication AP-117. February 1973.
Telecon. Raybestos-Manhattan, Inc. with David Cook, GCA Corporation.
February 28, 1980. Friction products manufactured.
Telecon. Kevin Peppard, Bendix Corporation, with David Cook, GCA Corpora-
tion. February 28, 1980. Friction product manufacturers.
Telecon. H.K. Sleeth, Porter Company, with Robert Bouchard, GCA Corpora-
tion. February 29, 1980. Friction products manufactured.
Telecon. Terry Blaine, Borg-Warner Corporation, Spring Division with
Robert Bouchard, GCA Corporation. March 4, 1980. Friction products
manufactured.
Telecon. Roy Huckabee, Nuturn Company, with Robert Bouchard, GCA Corpora-
tion. February 29, 1980. Friction products manufactured.
Telecon. Earl Fygert, National Friction Products Corporation, with
Robert Bouchard, GCA Corporation. February 29, 1980. Friction products
manufactured.
Telecon. Bill Shine, Auto Specialists Manufacturing Company, with
Robert Bouchard, GCA Corporation. February 29, 1980. Friction products
manufactured.
Telecon. Standco Industrial with Robert Bouchard, GCA Corporation.
February 28, 1980. Friction products manufactured.
Telecon. Jack Payton, Friction Products Company, with Robert Bouchard,
GCA Corporation. February 29, 1980. Friction products manufactured.
Telecon. Andrews, Royal Industries Brake Products, Inc. with Robert
Bouchard, GCA Corporation. February 28, 1980. Friction products
manufactured.
Telecon. Montgomery, Reddaway Manufacturing Company with Robert
Bouchard, GCA Corporation. February 29, 1980. Friction products
manufactured.
Telecon. Molded Industrial Friction Corporation with Robert Bouchard,
GCA Corporation. March 3, 1980. Friction products manufactured.
112
-------
28. Telecon. Wheeling Brake Block Manufacturing Company with Robert
Bouchard, GCA Corporation. February 29, 1980. Friction products
manufactured.
29. Telecon. Brassbestos Manufacturing Corp. with Robert Bouchard, GCA Cor-
l>ariit Ion. Mfirch 3, 1980. Friction products manufactured.
30. Telecon. Paul Biondo, Auto Friction Corp., with Robert Bouchard,
GCA Corporation. March 3, 1980. Friction products manufactured.
31. Telecon. Robert Randolf, Gatke Corporation, with Robert Bouchard,
GCA Corporation. March 3, 1980. Friction products manufactured.
32. Telecon. Lasco Brake Products Company with Robert Bouchard, GCA Corpora-
tion. March 3, 1980. Friction products manufactured.
33. Telecon. Appollageno, MGM Brakes, Inc., with Robert Bouchard, GCA
Corporation. March 3, 1980. Friction products manufactured.
34. Telecon. Carlisle Corporation with Robert Bouchard, GCA Corporation.
March 3, 1980. Friction products manufactured.
35. Telecon. Thiokal Chemical Corporation with Robert Bouchard, GCA Corpora-
tion. March 3, 1980. Friction products manufactured.
36. Telecon. Joseph Minky, P.T. Brake Lining Company, Inc., with Robert
Bouchard, GCA Corporation. March 4, 1980. Friction products
manufactured.
37. Telecon. Mr. Baltz, Baltz Company, Inc. (distributors for Eaton Cor-
poration), with Robert Bouchard, GCA Corporation. March 4, 1980.
Friction products manufactured.
38. Asbestos: An Information Resource, R.J. Levine, ed. DHEW Publication
Number (NIH) 79-1681, U.S. Department of Health, Education and Welfare,
National Cancer Institute, Public Health Service, Bethesda, Maryland.
May 1978.
39. Daly, A.R., A.J. Zupko and J.L, Hebb. Technological Feasibility and
Economic Impact of OSHA. Proposed revision to the Asbestos Standard
(construction excluded). Roy F. Weston, Environmental Consultants for
Asbestos Information Association/ North America, Washington, D.C.,
March 29, 1976.
40. Suta, B.E. and R.S. Levine. Nonoccupational Asbestos Emissions and
Exposures. In: Asbestos, Volume 1, Properties, Applications and
Hazards. L. Michaels and S.S. Chissick, eds., John Wiley & Sons,
New York, N.Y. 1979. pp. 171-205.
113
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41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
Gregg, R.T. Development Document of Effluent Limitations Guidelines
and New Source Performance Standards for the Textile, Friction Materials
and Sealing Devices Segment of the Asbestos Manufacturing Point Source
Category. U.S. EPA Report No. EPA 440/l-74-035a, December 1974.
Jacko, M.G. and R.T. DuCharme. Brake Emission: Emission Measurements
from Brake and Clutch Linings from Selected Mobile Sources. U.S. NTIS
PB-222 372. 1973.
Lynch, J.R. Brake Lining Decomposition Products. J Air Pollution
Control Association. 18(12):824-826. December 1968.
Hatch, D. Possible Alternatives to Asbestos as a Friction Material.
Ann Occup Hyg. 13:25-29. 1970.
Hickish, D.E. and K.L, Knight. Exposure to Asbestos During Brake
Maintenance. Ann Occup Hyg. 13:17-21. 1970.
Bush, H.D. , D.M. Rowson and S.E. Warren. The Application of Neutron
Activation Analysis to the Measurement of the Wear of a Friction
Material. Wear, 20:211-225. 1972.
Anderson, A,E., R.L. Geacer, R.C. McCune, and J.W. Sprys. Asbestos
Emissions From Brake Dynamometer Tests, Paper 730549 presented at
SAE Automotive Engineering Meeting, Detroit, Michigan. 1973.
Jacko, M.G., R.T. DuCharme and J.H. Somers. How Much Asbestos do
Vehicles Emit? Automotive Engineering, 81:38-40. 1973.
Rohl, A.N., et al. Asbestos Exposure During Brake Lining Maintenance
and Repair. Environmental Research. 12:110-128. 1976.
Alste, S., D. Watson and J. Bagg. Airborne Asbestos in the Vicinity
of a Freeway. Atmos Environ. 7:583-589. 1976.
Rohl, A.N. et al. Asbestos Content of Dust Encountered in Brake
Maintenance and Repair. Proc Roy Soc. Med. 70:32-37. 1977.
Bruckman, L. and R.A. Rubino. Monitored Asbestos Concentrations in
Connecticut, J Air Pollution Control Association. 28(12):1221-1226.
December 1978.
Federal Register, Commercial and Industrial Use of Asbestos Fibers;
Advance Notice of Proposed Rulemaking, Wednesday October 17, 1979, Vol. 44,
No. 202. p. 60062.
Unpublished N10SH data presented at American Industrial Hygiene
Conference, New Orleans, Louisiana. May 5, 1977.
Telecon. Bill Ferk, Scan-Pac Manufacturing Comp.my, Mequon, WI (414)
241-3890, with Nancy Krusell, GCA Corporation, GCA Technology Division.
April 22, 1981.
114
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SECTION 6
ASBESTOS-CEMENT PIPE
INTRODUCTION
Asbestos-ccment (A/C) pipe, an admixture of asbestos fibers and portland
cement, was introduced into the U.S. market in 1931.1 This corrosion resis-
tant pipe had been developed for the high pressure, salt water street flushing
system of Genoa, Italy. Worldwide use increased from about 321,800 kilometers in
service in 1950 to about 2,252,600 kilometers in 1970.2
Estimates of A/C pipe in domestic use vary widely. Industry estimates
of A/C pipe use were unavailable.3 The estimates of the amount of pipe in
service range from 160,900*'5 to 321,800 kilometers. A 1978 estimate by
Meylan et al.6 placed the number closer to 611,920 kilometers. The wide varia-
tion in estimates may be due to the type and use of the A/C pipe. The lower
number reflects pipe used for water and sewer transmission lines only. Over
50 percent of all A/C pipe sold in the U.S. is for high pressure water conduits;
next in quantity is nonpressurized sewer pipe, and the remainder includes a
wide range of applications including telephone and electrical wire conduit
and air ducting.
In 1980, according to the U.S. Bureau of Mines,7 A/C pipe consumed some
144,000 metric tons of asbestos, or about 40 percent of total consumption.
This approximation was based on Bureau of Mines data and compares with similar
approximations of 36,080 metric tons for floor tile, 43,700 metric tons for
friction products and 90,020 metric tons for paper products (including
roofing).* Generally speaking, asbestos consumption parallels new construc-
tion but in 1976-1977, the former declined while the latter climbed, possibly
an Indication of "loss of markets because of environmental problems."8 Also
in 1976 A/C pipe imports began to increase dramatically (Figure 11). Geo-
graphically, A/C pipe markets are larger in the faster growing sections of
the country west of the Mississippi rather than in the east where water sys-
tems generally have been in the ground for many years.8
*These consumption figures are for GCA-defined product categories. Other
sources (for example, see Reference 8) claim that A/C pipe is second to
roofing as the largest asbestos user. The apparent discrepancy results
from different product categorization.
115
-------
30
25
20
O
!/>
c
o
73% FROM MEXICO
27% FROM CANADA
1974
1975
1976
1977
1978
1979
YEAR
Figure 11. U.S. A/C pipe imports in millions of pounds of pipe.9
116
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PRODUCT DESCRIPTION
Composition
Pipe Specifications—
Specifications for A/C pipe ranging in internal diameter from 0.1 to 1.07
meters have been set by the American Water Works Association.1 Standard length
is 3.96 meters and random lengths less than 2.13 meters are not recommended.
The pipe is classified on the basis of its design internal pressure, ranging
from 21.1 to 63.3 kg/cm2. The pipe is also chemically classified as follows;
• Type I—no limit on uncombined calcium hydroxide
• Type II—1 percent or less uncombined calcium hydroxide
The pipe's ability to withstand attack (and possible resultant release of
asbestos fibers) from "aggressive" water* depends upon this chemical type.
Only Type II is recommended for moderately aggressive water whereas either
Type I or II can be used for nonaggressive water.* For external corrosion
from soil water, in addition to acidity, soluble sulfate is an important
parameter in determining pipe durability.1
Formulations—
If the pipe material simply sets under specified conditions++ (Type I)
representative formulations are 15 to 25 percent asbestos and 75 to 85 percent
cement; however, if the pipe is "cured" by autoclave (Type II) - the practice
in the U.S. - silica is added so that a representative formulation becomes 15
to 25 percent asbestos, 42 to 53 percent cement, and 34 to 40 percent silica.
Up to 6 percent finely ground solids from crushed damaged pipe may be added
as a filler material. The average asbestos content is 18 to 20 percent.6 In
1980, 83.2 percent of the asbestos used in A/C pipe was chrysotile, grades 4
through 7; 16.7 percent was crocidolite; and 0.1 percent was amosite.7
Uses and Applications
The majority of the A/C pipe produced is used for water mains (pressure
pipe) and sewer lines (nonpressure pipe). The exact historical use break-
down is unavailable as this information is considered confidential and/or
unknown. An indeterminate, smaller amount of A/C pipe is also used as con-
duits for electrical and telephone cables, air diets, and for laterals from
street mains to the user.
Special Qualities
A/C pipe products are strong, resilient, flexible, durable, inert, and
corrosion resistant. Asbestos imparts a flexural strength in pipe which allows
for a certain amount of deflection without failure. The laminar structure of
*Aggressiveness is defined as: pH + log (AH) where A is the total alkalinity
and H the total hardness, both expressed as ppm CaCOg. Highly aggressive
water has a value of pH + log (AH) <10.0; moderately aggressive a value of
«10.0 to 11.9, and nonaggressive a value of 342.0.1
+Tbe serviceability of Type II pipe for aggressive water applications should be
established by the purchaser in conjunction with the manufacturer.
^ Emursed in water for a period of 28 days.
117
-------
the pipe, which results from the basic method of manufacturing, also contri-
butes to greater strength.8 This allows for easy tapping for lateral line or
other connectors without a loss of strength. Because of the nature of the
raw materials (Portland cement and asbestos fibers) used to manufacture A/C
pipe, it resists corrosion and most chemical action, and is not subject to
electrolysis.
The primary purpose of asbestos fibers in A/C pipe is to act as a rein-
forcing .igent. Properties which make asbesLos suitable as a reinforcing
agent are its high fiber strength, resistance to alkali attack, and adhesion i. >
cement. The raw fibers are also readily wetted and thus contribute favorable
and controllable drainage properties to an asbestos cement mix enabling A/C
pipe to be produced by a relatively simple and flexible process similar to
that used in papermaking.10 Asbestos can also withstand the autoclave (heat
and pressure) process in the manufacture of pipe and resists the alkali
attack of Portland cement. The large surface area of asbestos fibers promotes
good adhesion between the cement mixture and the fiber surface.
SUBSTITUTES
Fiber Substitutes
Fiber substitutes for asbestos as a strengthening fiber in cement pipe
are not currently considered cost-competitive. Potential fiber substitutes,
which include glass, metals, graphite and various natural fibers, have not,
to date, proven to be equal to asbestos as a fiber replacement. Although glass
fibers are possibly the best fiber substitute, they are two to four times
more costly than the equivalent asbestos fibers and tend to dissolve in the
highly alkaline cement matrix.11 To circumvent this difficulty, recently
developed alkali-resistant glass fibers are being examined, but they are four
to seven times more costly than equivalent asbestos fibers. Glass is being
substituted for asbestos in some couplings and fittings, maintaining strength
by greater thickness.
Pipe Substitutes
Pipe substitutes include ductile iron pipe, concrete pipe, plastic pipe and
vitrified clay pipe. None of these products alone could substitute for all
asbestos cement pipe uses; however, as a group, they can meet all the technical
requirements placed on asbestos cement pipe.1
Asbestos cement pipe is economically the most suitable for intermediate
range pipe diameters (0.15 to 0.61 meters). However, even in this size range,
it is not always the preferred choice. Ductile iron is more suited for situ-
ations involving shock loads, vibration and ground movement in general.13 In
addition, the number of asbestos cement pipe manufacturing facilitiPS is small
and transportation costs may be substantial.
In the range of small pipe diameters, plastic pipe, vitrified clay pipe
and iron pipe all offer strong competition. For very large pipe sizes,
reinforced concrete pipe is preferred.'*
118
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MANUFACTURING
Primary Manufacture
The manufacturing process for A/C pipe is similar to the wet mechanical
process for making A/C sheet and related products. The basic process is
outlined in Figures 12 and 13 and is used by most manufacturers. As with any
process, minor variations between different plants may exist. The following
description is bastd upon literature descriptions and a site visit to an A/C
pipe plant.114
The process starts with the arrival of the raw asbestos fibers at the
plant. Asbestos is usually transported by truck or railcar. Weight of the
individual bags of fiber varies but 100 lb (or 50 kg) bags are common. Pack-
aging of the fiber varies, but it is usually wrapped in plastic and/or Kraft
paper bags. Fibers may be loose or pressed into "bricks" in the bags. Asbes-
tos shipped as "bricks" is becoming popular because this form could reduce the
potential for air emissions due to ripped bags or spillage.
The bags of fiber may be loaded individually or, as is common in large
single container shipments, placed on pallets to facilitate forklift moving.
Palletized bags of asbestos are often shrink-wrapped with plastic to further
reduce the potential for fiber release. The received fiber is stored in a
warehouse prior to use.
The fibers are transported from the central storage area to the head of
the production line by forklift or manually. The asbestos is opened, weighed,
and added to the dry mixer. Other ingredients including Portland cement and
possibly sand are added. The dry mixer serves to fluff the asbestos fibers
and prepare a uniform mixture.
From the dry-mixer the dry mix is conveyed to the wet-mixer or beater
where water is added to make an A/C slurry consisting of approximately 97
percent water. The slurry flows or is pumped to the pipe-forming machine vats
where it is deposited on one or more rotating, horizontal, cylindrical screens.
Excess water is removed from the slurry layer on the screen. The resulting
layer of asbestos-cement material, 0.5 to 2.5 mm thick, is transferred to
an endless-felt conveyor belt that travels over suction boxes to remove water.
The wet mat is then transferred to a mandrel or accumulator roll which winds
the mat into pipe (or sheet) stock of the desired thickness. Pressure rollers
bond the mat to the layer previously deposited and remove further excess water.6
The pipe is usually cast in 3.05 to 4.6 meter lengths.
The pipe is removed from the mandrel, air cured, and final cured in an
autoclave using saturated steam. The pipe may, as a final step, be lined with
a coating to further increase its corrosion resistance and improve flow char-
acteristics. Vinyl is a commonly used liner.
The finished pipe is sent to stock, which may be in the open. Stock is
often palletized to form uniform loads and facilitate handling. This operation
also reduces breakage.
119
-------
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u> tem%tm
m
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a tuctRo** vmi*
I MlfM'Mll
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ft vchiin i uinum *«m
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4*1 rii itrm ll %iiMi
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Mf causo nwnnMm**H
I'i^ure 12. Manufacture of asbestos-cuinimt pipe.
120
-------
MOLDING
STOCKEN
MANDREL
RECEIVING AND WAREHOUSING
BAG OPENING
WEIGH MIX
WATER
RECYCLED SOLIDS
RECYCLED WATER
* WASTEWATER
STEAM
ELECTROLYTIC LOOSENER AND
PRECURE CONVEYOR
»CONDENSATE
SOLIDS
WATER
RECYCLED
WATER
* WASTEWATER
WET MIX
FORMING
FINISHING
STORAGE
HYDROSTATIC
TESTING
PIPE END
FINISHING
CURING
(AUTOCLAVE)
CLARIFICATION
(SAVE-ALL)
RAW MATERIALS
STORAGE
PROPORTIONING
ORY MIX
CONSUMER
Figure 13. Flow diagram of asbestos-~cement pipe manufacturing
operations by the wet mechanical process.1S
121
-------
Manufacturing Plants
The locations and estimated 1975 sales figures for A/C pipe plants in the
U.S. are given in Table 30. The major plants listed in this table are estimated
to account for more than 95 percent of total A/C pipe production in the U.S.
These plants are primary manufacturers and there is no secondary fabrication
of A/C pipe.
Production Volumes
Recent, reliable production volumes of A/C pipe are considered proprietary
and are unavailable. The total quantity of asbestos consumed by A/C pipe in
1980 was 144,000 metric tons,7 but recent information concerning the asbestos
consumption or pipe production of individual plants is not available.
Projected trends for A/C pipe consumption vary from modest growth (5 to
7 percent for the next 3 to 7 years), through market stability,6 to actual
decline. PVC pipe inroads on the water pipe market are predicted to be prim-
arily at the expense of ductile iron pipe rather than A/C pipe. However, in
the case of sewer pipe, especially in the southern half of the U.S. where
higher temperatures and lower flow rates accelerate acidic deterioration of
A/C pipe, PVC pipe may claim a substantial share of the market, perhaps even
eventually displacing A/C pipe if the latter's cost cannot be lowered.8
ASBESTOS RELEASE
Input/Output
A mass balance for asbestos use within the A/C pipe industry was con-
structed and may be found in Figure 14. The figures were achieved by incor-
porating Levine's16 1974 estimates projected to 1980 U.S. Bureau of Mines7
consumption figures. Of the 144,000 metric tons entering the process as raw
asbestos fiber, approximately 140,346 metric tons are incorporated into the
product and 3,599 metric tons are sent to disposal as vacuum cleaner and
baghouse dust, product scraps, and clarifier sludge. An estimated 14 metric
tons escape through a control device (typically a baghouse). Levine's atmo-
spheric emission estimates are based on gross assumptions with a reported
uncertainty of at least an order of magnitude. Meylan6 reports emissions of
1 to 3 orders of magnitude less. Atmospheric emissions from disposal, based
on GCA estimates, are shown to be 7 metric tons. This estimate is loosely
based on Levine's data, and takes into account new regulations adopted in
1975 regarding the disposal of asbestos.
During Manufacture
Workplace Exposure—
Exposure to asbestos fibers may occur during manufacture. Table 31 shows
some asbestos exposure levels within A/C pipe manufacturing facilities. The
OSHA workplace standard is currently 2 fibers/cc based on an 8-hour time
weighted average (TWA).
122
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TABLE 30. LOCATION AND SALES OF MAJOR A/C PIPE PLANTS
6, a
Company
Plant location
Estimated
1975 sales
Percent of
market** »c
Estimated a.ibestos
consumption^
(thousand metric tons)
Johns-Manvllie
Manville, N.Te,h
S 78,000,000
42\
54
Johns-Manvilie
Waukegan, II.6'*1
15,000,000
8
11
Johns-Manvllie
Denison, TX
14,400,000
7
76
10
Johns-Manvilie
Green Cove Springs, FL*5
5,700,000
3l
4
Johns-Manville
Long Beach, CA
29,000,000
V
20
Johns-Manville
Stockton, CA
-
-
-
Certain-Teed
Santa Clara, CA
A,600,000
2)
3
Certain-Teed
Hillsboro, TX
8,700,000
*
6
Certain-Teed
Ambler, PA
7,200,000
M
19
5
Certain-Teed
St. Louis, HO
10,400,000
6)
7
Certain-Teed
Riverside, CA
2,200,000
i
2
Capco Corporation
Ragland, AL
4 ,300,000
2 )
3
(Cement Asbestos
Products Co.)
Capco Corporation
Flintkote Company
Van Buren, AR
Ravenna, 0H^
8,700,000
$188,200,000
139'
Augmented by GCA telephone contact.
^To the nearest whole number.
Excluding Stockton plant.
^Excluding Stockton plant but based on a total consumption which presumably includes this plant.
g
Plant also manufacturers other asbestos products.
^Closed in 1976.
g
U.S. Bureau of Mines estimates,
^ot producing pipe at this time.
-------
MANUFACTURING OPERATIONS
DRY
MIXING
(AC
OPENING
PIPE
FORMATION
lW.jW TPY
SAGHOUSE
EMISSIONS
Hi TPY
LEGEND
C iNPUT/ouTPinr
| 1 MANUFACTURING
1 PROCESSES
WATER
EMISSIONS
LAND
DISPOSAL
EMISSIONS
DISPOSAL
EMISSIONS
7 TPY
CONTROL EQUIPMENT
21 TPY
}li TPY
3.599 TPY
u ULTIHATE DEPOSITION
SOL 10
— — • WATER
AIR
Figure 14- Input/Output of asbestos disposal and emissions for the asbestos cement pipe industry,
(metric tons).
-------
TABLE 31. ASBESTOS-CLMENT PIPE MANUFACTURE - ASBESTOS
EXPOSURE LEVELS17
Process-related work areas
Asbestos exposure
levels (fibers/cc)
Fiber receiving and storage
Fiber introduction i
Dry mix - wet mix I
Pipe formation
Air/cure/autoclaving
Pipe finishing
Sawing
Finishing lathes
Coupling cutoff machinery
Fitting and specialties
Dril1ing
Rework saw and crushing
Quality control inspection
Floor sweeping
0.2 - 2.5 TWA
0.1 - 4.8 TWA
0.4 - 3.0 TWA
0.1 - 1.4 TWA
0.2 - 0.3 TWA
a
0.1 - 1.9
TWA
0
1
o
TWA
0.2 - 2.3
TWA
1.5 - 2.1
TWA
<0.1 - 0.5
TWA
2.0 - 2.9
TWA
<0.1 - 0.2
TWA
<0.1 - 0.3
TWA
TWA - 8-hour, Time-Weighted Average.
"'it is not clear whether the fibers counted are free fibers
or whether asbestos fibers attached to or partially im-
bedded in cement particles are also counted.
125
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Workplace exposures may take place at virtually every step of the produc-
tion process, but the potential is greatly reduced as the process proceeds.
Initially, the fibers are dry and could easily become airborne. Once the fibers
have been wetted the potential for exposure decreases. The final product should
have little or no potential for fiber release since the fibers are in a cement
matrix.
Exposure at fiber receiving docks and storage areas would arise if broken
bags of fiber are present. Careful handling will prevent breakage. Repairing
rips immediately will remove the fiber release threat. In addition, the
packaging of the fibers as bricks will reduce the fiber release if a rip in
the packaging does occur.
Bag opening, prior to introduction Into the dry mixer may present the
potential for the highest level of worker exposure. This operation is largely
done manually. Exposure risk is greatly reduced if the bags are opened in
enclosed "glove boxes" which are also aspirated. The exclusive use of mechan-
ical opening devices is hampered by the lack of standardized packaging.
Dry mixing creates large amounts of dust but this dust is typically
controlled with air pollution devices like cyclones and baghouses. Once the
mixture is wetted the potential for exposure is greatly reduced. However,
this wet mixture is very messy. Inevitably there is spillage which forms on
machines and may be picked up by workers on their clothes and shoes. Proper
precautions must be taken to reduce exposure from this occurrence.
Housekeeping may have a fiber release associated with it. Cleanup is
preferably performed either with a vacuum or by washing. These methods reduce
the dust which may be created by sweeping. All wastes should be carefully
packaged to prevent fiber release during disposal.
In the finishing area pipe is machined, cut or worked, and these operations
have the potential to create air emissions. Emissions may be minimized by the
use of wet saws and drills or by performing the work under well aspirated hoods
and enclosures (which vent through some type of air pollution control device).
Proper housekeeping procedures should be followed to ensure safe cleanup.
Emissions to Air—
Actual measurements of asbestos fiber concentration in the vicinity of an
asbestos cement manufacturer are very limited. However, Suta and Levine
estimated concentrations near asbestos industrial facilities using mathemati-
cally derived dispersion curves of assumed plant emissions. In the case of
asbestos cement, it was estimated that a population within 5 km of a manufac-
turing plant would be exposed to a median asbestos concentration of 27.0 and
7.2 ng/m3 for urban and rural facilities, respectively. Comparing this data
with the median U.S. atmospheric fiber concentration (20 ng/m3),1 it appears
that asbestos cement manufacturing contributes little to nonoccupational
exposure. Actual ambient monitoring in the vicinity of an asbestos cement
facility is necessary to confirm Suta and Levine's estimates.
126
-------
Release to Water—
Raw wastewater discharge from A/C pipe manufacturing plants typically
rontulna about 2.86 kilograms of suspended solids per metric ton of product.15
TIu'hl' solids Include organic materials such as grease, tar, oils, fats, non-
asbestos fibers, and sawdust as well as inorganic materials such as sand, silt,
clay, and cement in addition to asbestos. The amount of asbestos in the waste
stream is relatively low compared to the cement, silica, and clay raw materials.
Using Levine's estimates, scaled to 1980 consumption figures, it is estimated
that 34 metric tons of asbestos is released to the water from A/C pipe
production.
In the United States, approaches to the treatment of wastewaters from
A/C product facilities vary widely from plant to plant, ranging from no
treatment at all to 100 percent water recycling in some of the larger plants.
Most asbestos plants do have some form of sedimentation treatment for their
water, either a clarifier or a sedimentation pond. The settled sludge is
usually hauled away to a landfill, while the clarifier water is recycled or
discharged to surface waters or sewers. The overall efficiency of this treat-
ment process is estimated to be about 94 to 96.7 percent.15
Release to Land—
On the basis of an examination of the waste pile of one asbestos products
plant, Harwood and Ase19 found that about 5 to 10 percent of the A/C product
material is dumped as scrap of which about 10 percent is fine dust from bag-
houses, and 90 percent is coarse scrap from trimmings, breakage, and rejected
product. They concluded that asbestos-manufacturing plant waste piles pose a
potential emission hazard to nearby populations; however, because of variations
in climate, moisture, and operating procedures, they found it impossible to
quantify such emissions. The troublesome material appears to be the baghouse
fines. Possible solutions to the problem are: (1) pelletizing the dust,
(2) encapsulating it in cement or some other solid matrix, and (3) reprocessing
the material. In the last case, baghouse fibers are too short to add strength
to the cement matrix. Several plants2 mix baghouse fines with cement and then
dispose of them in landfills, which are commonly located on company grounds.
Harwood and Oestreich20 report measurements for their study made downwind
from the dump of an A/C pipe plant (Table 32), but, Inasmuch as they fail to
report upwind values or the dump's location (so that a guess can be made of
background levels), their numbers are not very useful for estimates for this
report. The authors also discuss water, foam sprays, chemical fixation, vege-
tative stabilization, and waste commingling as dust control measures at dump sites.
During Use
Installation Exposure—
One of the major advantages of A/C pipe is the ease of installation and
the quality of joints and fittings. There is relatively little in situ saw-
ing, cutting, drilling, or machining of A/C pipe necessary during installation.
The onsite fabrication that is required, however, may lead to high instan-
taneous (15-minute) fiber concentrations. One industry study21 reported peak
127
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fiber counts of up to 64 f/cc when an abrasive disc is used to cut A/C sewer
pipe. However, this and similar cutting and drilling operations occupy only
1.1 percent of total field installation time,21 and the 8-hour time weighted
asbestos concentration for these operations is still below the 2 f/cc occu-
pational limit. Thus, while there may be transitory worker exposure, there is
little likelihood of significant asbestos fiber release into the environment,
especially since the fibers are immobilized in the cement matrix. A/C pipe,
it should be noted, is not a consumer product. Installation is almost always
by professional workers, who should be familiar with installation procedures.
However, in the case of the enlargement or modification of existing water
pipeline systems, Millete, et al. z cite evidence that residents may have been
exposed to transitory increased asbestos levels in drinking water as a result
of improperly performed pipe tapping work. Available tapping devices flush
cutting debris away, thereby avoiding contamination. The American Water Works
Association has published1 recommended work practices for shipping, handling,
and installation of A/C pipe including both dry and wet tapping.
TABLE 32. REPRESENTATIVE FIBER COUNT VALUES OBTAINED AT THREE
ASBESTOS WASTE DUMPS (FROM HARWOOD AND OESTREICH)2 0
Dump
site
Sampler
Optical microscope
data—fibers
1.5-30 yin length
(fibers/m3)
Electron microscope
data—fibers
0.05-1.5 nm length
(fibers/m^)
Location
(meters)
Elevation
(meters)
Asbestos
cement
pipe
plant
710
downwind
2
1.7 x 106
6.2 x 106
7
1.9 x 1014
6.7 x 106
General
asbestos
products
plant3
336
downwind
2
2.0 x 102
1.5 x 108
7
2.5 x 102
2.7 x 108
Asbestos
ore
mill
224
downwind
2
9.3 x 105
5.9 x 108
7
7.3 x 105
aIncluding A/C pipe.
User Exposure—
The principal avenue of asbestos exposure for users of asbestos concrete
pipe is the potable water which is transported through the pipe. Responding
to concern about the possible contamination of drinking water by A/C pipe
conduits, an American Water Works Association committee carefully reviewed
the problem in I97A.23'ZI* Their findings were based primarily on work by the
Johns-Manville Research Center which examined two municipal A/C pipe systems
over a 1-year period and found that on the average the asbestos content of the
128
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water flowing out was only 4 x 103 to 70 x 103 fibers/I greater than the water
flowing in. Hallenbeck, et al.25 examined 15 A/C pipes located in northeastern
Illinois and found no significant release of chrysotile from the pipes. In a
detailed study which took water aggressiveness into consideration, Buelow,
et al.26 found little or no increase in asbestos fiber levels in nonaggressive
water transported through A/C pipe but significant increases in the case of
aggressive water. Reviewing these studies* Meylan, et al.6 conclude that
"use of asbestos-cement pipe for water transport does not seem to contribute
any large amounts of asbestos into the general environment."
Very recently a study of 365 urban water suppliers has been compiled.22
The findings are summarized in Table 33. This review concludes:
"The majority of persons receiving water from asbestos-cement pipe
distribution systems are not exposed to significant numbers of
fibers from the pipe. Many residents using asbestos-cement pipe
may be exposed to intermittent amounts of asbestos fibers in their
water if pipe tapping work is done Improperly. In areas of very
aggressive water (estimated to be 16 percent of the U.S. water
utilities) consumers using asbestos-cement mains may be exposed to
high concentrations of fibers, over 10 million fibers/A."
TABLE 33. DISTRIBUTION OF REPORTED ASBESTOS
CONCENTRATIONS IN DRINKING WATER
FROM 365 CITIES, 43 STATES, PUERTO
RICO, AND THE DISTRICT OF COLUMBIA22
Asbestos concentration
Number of
Percentage
(106 fibers/1)
cities
of samples
Below detectable limits
110
30.1
Nol statistically significant
90
24.6
Less than 1
90
24.6
1 to 10
34
9.3
Greater than 10
41
11.2
Total
365
99.8
In only one community, Blshopville, S.C., did the maximum fiber level,
547 x 10® f/1), believed to be attributable to release from corrosion of A/C
pipe by aggressive water, exceed the maximum levels found in anthropogenically
uncontaminated natural waters (130 x 106 fibers/1 for San Francisco—fibers
from the natural erosion of serpentine rock). Unfortunately, information as
to the representativeness of the samples and the reproducibility of these
maximum values l'ound was not included. No unequivocal evidence is given that
proves asbestos fiber release from A/C pipe increases fiber levels outside
the range encompassed by uncontaminated natural waters. On the other hand,
there is no question as to the fact that highly aggressive water can corrode
129
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A/C pipe and that asbestos fibers must be released as a consequence. In the
case of sewer systems, pipe deterioration might also be generated by the dump-
ing of highly aggressive chemicals into sewer pipes. A/C pipe may also be
corroded from the outside by certain soil conditions. This corrosion of the
pipewall should not contaminate the water flowing within and, inasmuch as
migration of asbestos fibers in soils is ordinarily exceedingly slow,27 it
would not be apt to create any hydrospheric or atmospheric contamination
problem.
Finally, asbestos fibers released to the water from A/C pipe may poten-
tially become airborne. Meylan, et al.6 studied the possibility of this air
emission when the water is atomized in certain types of commercial and re-
sidential humidifiers. They made a rough estimate that the asbestos level
in the air of a house might be raised by as much as 6 x 10s fibers/m3 with
humidifier use. No ambient air sampling has yet been conducted to substantiate
this estimate.
If It can be established that fiber release from A/C pipe does in fact
represent a hazard to the public health, a number of corrective alternatives
are available including:
1. Do not use A/C pipe to carry highly aggressive waters.
2. Pretreat the water to reduce aggressiveness.
3. Filter the water after passage through the A/C pipe.
4. Coat the inside of the pipe with a protective material designed
to prevent pipe corrosion and reduce fiber release.
5. Substitute other pipe materials, provided, of course, they do
not represent a greater health hazard than A/C pipe.
During Disposal
Because of its relatively recent introduction (about 50 years ago) and
very long service life, there is a paucity of information concerning the
abandonment and/or disposal of A/C water pipe supply systems. Except under
very aggressive water conditions, practically speaking, once in the ground,
A/C pipe lasts forever. Engineering standards recommend that urban lines be
replaced every 75 years.28 However, this is often not the case due primarily
to the lack of monies and the inconvenience of digging up streets. The water
line replacement cycle in New York City is 300 years and in Jersey City 500
years.28 In high population density urban areas, A/C pipe when replaced,
might be removed, crushed, and trucked to a landfill. In lower density areas,
the old pipe might be left in the ground and new pipe laid down beside it.
In the former case, there should be minimal asbestos fiber mobilization from
the old pipe and in the latter instance, none.
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CONCLUSION
Asbestos-cement pipe has many qualities which make it suitable for use
under a variety of conditions. However, only modest growth is expected in the
near future. One reason is the abundance of satisfactory product substitutes
such as plastic pipe (PVC), ductile iron pipe, vitrified clay and cement pipe.
These pipes may have equal or superior qualities and enjoy a price advantage,
particularly as transportation costs rise, as there are few A/C pipe plants
and many of the other pipes are locally produced. The demand for all pipe
will plateau as new construction decreases. With replacement schedules lagging
years behind due to financial considerations, A/C pipe cannot reasonably be
expected to have continuous high growth.
The potential for human exposure to asbestos from the manufacture and use
of A/C pipe exists. Workers in A/C pipe plants may be exposed to asbestos
fibers in the air in excess of OSHA workplace standards, especially in fiber
receiving and storage and dry mixing areas (up to 4.8 fiber/cc TWA). Imper-
missible levels also may occur as the result of cutting, drilling, and machin-
ing operations. These same operations during pipe installation may also expose
workers for short periods of time to significant fiber levels (up to 64 fiber/
cc TWA). In areas where the water is highly aggressive, there may be a release
of asbestos fibers from A/C pipe into water systems. However, appropriate
abatement of any excessive fiber levels appears to be feasible.
Existing sampling data are inadequate to draw accurate conclusions on
the levels of asbestos in the general environment attributable to A/C pipe.
More accurate data are needed on the quantities of asbestos released to the
environment due to the production and subsequent use of A/C pipe.6 Sampling
must be conducted to ascertain fugitive emissions, storm run-off levels and
possible transport on work clothing. Despite the Millette, et al.22 report,
data is generalLy lacking on fiber release from water systems and wastewater
pipes. This is perhaps the greatest data need, as waterborne asbestos poten-
tially affects the greatest number of people. Specifically, with respect to
potable water, reproducible average asbestos concentrations are needed as a
function of A/C pipe length, suspended solids content, temperature and water
aggressiveness. Such data is needed on both inlet and outlet water streams
to quantify the specific source of the asbestos fibers.
131
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REFERENCES
1. American Water Works Association. AWWA Standard for Asbestos-Cement
Transmission Pipe, 18 in. through 42 in. for Water and Other Liquids.
AWWA C402-77. January 30, 1977.
2. Olson, H. L. Asbestos in Potable Water Supplies. J. American Water
Works Association. 66. 515-518. 1977.
3. Letter from Ed Mussler, GCA Corporation to Joe Jackson of Asbestos Cement
Pipe Producers Association. January 30, 1980. Notebook 3. Call 3.
4. Survey of Water Main Pipe in U.S. Utilities over 2500 Population.
American City. Morgan-Grampian Pub. Co. Pittsfield, MA. 1975. p. 52
5. Survey of Sewer Main Pipe in U.S. Utilities over 2500 Population.
American City. Morgan-Grampian Pub. Co. Pittsfield, MA. August 1975.
p. 33
6. Meylan, W. M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination:
Task III—Asbestos. EPA 560/6-78-005. August 1978.
7. Clifton, R. A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of Mines.
Washington, D.C.
8. Wright, M. D., et al. Asbestos Dust Technological Feasibility Assessment
and Economic Impact Analysis of the Proposed Federal Occupational Standard:
Part I. U.S. Department of Labor. 0SHA. September 1978. (Draft)
9. Asbestos Magazine. January 1980. p. 4.
10. Michaels, L. and Chissick, S. S., eds. Asbestos: Volume 1, Properties,
Applications, and Hazards. John Wiley and Sons. New York, NY. 1979.
11. Farahar, R. M. Glass Reinforced Concrete. Publication of Unknown Origin.
Received from Cem-FIL Corp., Nashville, TN, in response to phone call
from Ed Mussler, GCA Corporation. GCA No. 7-03-007-0035. 6 p.
12. Preuti, Russell. American Concrete Pipe Association, 703/821-1990.
Personal communication with Ed Mussler, GCA Corporation. February 11,
1980. Notebook 3. Call 17.
13. American Pipe Manual, 15 ed. American Cast Iron Company.
Birmingham, Ala. 1979.
132
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14. LaShoto, P. W. GCA/Technology Division Trip Report on Visit to Johns-
Manville, Manville, N.J. October 22, 1979.
15. Carton, R. J. Development Document for Effluent Limitation Guidelines
and New Source Performance Standards for Building, Construction, and
Paper Segments of the Asbestos Manufacturing Point Source Category.
U.S. Environmental Protection Agency. U.S. National Technical Informa-
tion Service. PB-230. February 1974.
16. Levine, R., ed. Asbestos: An Information Resource. May 1978.
17. Chapman, J. H., et al. Asbestos Dust Technological Feasibility Assess-
ment and Economic Impact Analysis of the Proposed Federal Occupational
Standard: Part III. U.S. Department of Labor, OSHA. September 1978.
(Draft).
18. Suta, B. E., and R. J. Levine. Nonoccupational Asbestos Emissions and
Exposures. Asbestos, Properties, Applications and Hazards. Volume 1.
John Wiley and Sons, New York, N.Y. 1979.
19. Harwood, C. F., and P. K. Ase. Field Testing of Emission Controls for
Asbestos Manufacturing Waste Piles. Industrial Environmental Research
Laboratory, Office Research and Development, U.S. Environmental Protec-
tion Agency. Cincinnati, Ohio. 1977.
20. Harwood, C. F., and D. K. Ostreich. Asbestos Emissions from Baghouse
Controlled Sources. 1975.
21. Recommended Standard for Occupational Asbestos Exposure in Construction
and Other Non-fixed Work Operations. The Asbestos Information Asso-
ciation of North American and the Association of Asbestos Cement Pipe
Producers, Washington, D.C. February 7, 1980.
22. Millette, J. R., et ai. Exposure to Asbestos from Drinking Water in the
United States. Health Effects Research Laboratory Office of Research and
Development, U.S. Environmental Protection Agency. Cincinnati, Ohio.
August 1979.
23. Kuschner, K., et al. Does the Use of Asbestos-Cement Pipe in Potable
Water Systems Constitute a Health Hazard? J. Amer. Water Works Assoc.
66, 1-22. 1974.
24. Safe Drinking Water Committee. Drinking Water and Health. National
Academy of Science. Washington, D.C. 1977.
25. Hallenbeck, W., et al. Asbestos in Potable Water. University of Illinois
Water Resources Center. Report No. 178. January 1979.
26. Buelow, R. W., et al. Field Investigation of the Performance of Asbestos-
Cement Pipe Under Various Water Quality Conditions. Prepub. copy. Water
Supply Research Division, Municipal Environmental Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati, Ohio. 1977.
133
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27. Fuller, W. H. Movement of Selected Metals, Asbestos and Cyanide in Soil,
Applications to Waste Disposal Problems, Municipal Environmental Research
Laboratory, Office of Research and Development. U.S. Environmental Pro-
tection Agency. Cincinnati, Ohio. April 1977. EPA-600/2-77-020.
28. Epstein, A. Knight Ridder Service. Water and the Big Old City: Trouble
Ahead. Boston Globe, p. 1. October 9, 1979.
29. Craun, G. E., et al. Exposure to Asbestos Fibers in Water Distribution
System. Paper presented at Ninth American Water Works Association
Conference, Anaheim, Calif. May 1977.
134
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SECTION 7
ASBESTOS-CEMENT SHEET
INTRODUCTION
Asbestos-cement (A/C) products represent the largest single use category
of asbestos in the United States, accounting for approximately 42 percent of
total 1980 asbestos consumption.! Although A/C pipe is the largest component
of this product category, A/C sheet accounted for an estimated 7,900 metric
tons of asbestos use in 1980 or 2 percent of total U.S. market consumption.
A/C sheet has been employed since the late 19th century, when an Austrian
discovered a process for reinforcing cement using asbestos fibers. The first
A/C plants in the U.S. were constructed around 1900. Many A/C applications
first developed at that time are still in use today.
A/C sheet is currently used in many construction applications including
roofing and siding for both industrial and residential buildings. As such,
asbestos use in this industrial segment is highly dependent on changes in the
construction industry. This is demonstrated by the wide variation in asbestos
consumption for A/C sheet over the 1969 to 1980 time frame. During that time
asbestos use varied from a low of 7,900 metric tons in 1980 to a high of
86,000 metric tons in 1974.
Several distinct products are produced within the A/C sheet industry.
They include flat and corrugated sheet and siding and roofing shingles. The
relative production mix of these products is demonstrated by Table 34. This
table relates product distribution by the value of product shipments for
1967, 1972, and 1977.
PRODUCT DESCRIPTION
Composition
A/C products may contain from 10 to 70 percent asbestos, although these
are extreme ranges only found in specialty items. A/C sheet products typically
contain 30 to 40 percent asbestos, with chrysotile grades 6 and 7 the forms
most commonly employed.* Additional asbestos forms, including crocidolite
and amosite may be incorporated to enhance reinforcement, dispersion of fiber
and drainage properties of the A/C mix.^ Table 35 presents a breakdown of 1980
A/C sheet asbestos consumption by fiber type and grade.
135
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TABLE 34. SHIPMENT VALUES OF ASBESTOS-CEMENT SHEETS, INCLUDING A/C
ROOFING PRODUCTS 3'*
Total product shipments,
including interplant
transfers
(millions of dollars)
SIC product
code Product 1967 1972 1977
32929 41 Flat sheet and wallboard 15.2 20.7 25.3
32929 51 Corrugated sheets 3.5 5a 5^
32929 77 Asbestos cement shingles and 24.0 20.8 18.7
clapboard
Estimate made by authors of Reference 4.
^GCA assumes shipment value remains unchanged.
TABLE 35. A/C SHEET ASBESTOS CONSUMPTION IN 1980
(METRIC TONS)1
Chrysotile
Grade 5 100
Grade 6 4,300
Grade 7 3,500
Total asbestos 7,900
136
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Portland cement, the A/C sheet binder, is used in quantities ranging
from 25 to 70 percent. Consistent cement quality is very important as any
variations in the chemical content or fineness of the grind can affect produc-
tion techniques and final product strength.6 The remaining raw material,
from 5 to 35 percent of the total product composition, is finely ground
silica and any necessary dyes or pigments. Some A/C plants have onsite facil-
ities for grinding silica as part of their operations. Finely ground solids
from damaged A/C sheet trimmings may also be recycled in some plants for
filler material. A maximum of 6 percent of such filler material can be used
in some products before affecting the strength of the material.
The asbestos fibers in A/C products interweave to act as a reinforcing
medium in imparting increased tensile strength to the cement. As a result,
there is a 70 to 80 percent decrease in the weight of the product to attain
a given structural strength, which could not be accomplished without the
addition of a fibrous material such as asbestos to the cement. It is
important that the asbestos be embedded in the product in a completely fiber-
ized or willowed form. Willowing is frequently carried out prior to the
addition of cement and silica. However, in some cases this fiber opening
may be accomplished while the wet mixture is agitated by a pulp beater or
hollander.
Uses and Applications
A/C sheet is widely used in construction applications, including roofing
and siding both for industrial and residential buildings. It is also used in
the manufacture of such items as heaters, boilers, vaults and safes, electrical
pquipmenr mounting panels, and welding shields.
The flat sheet has a variety of construction uses. Different types of
this sheet are made, with densities varying according to the ultimate function
desired. Ordinary or hif»h density sheets mav be used for external cladding
applications and special low density panels containing a larger proportion of
ashestos fibers are designed for use as infill panels for curtain wall systems,
fire-resistant partitions, ducting, fume hoods, and doors.7
Currently, one of the larger areas of use for flat sheet is as a sub-
strate for curtain walls. In this application, the building contractor
applies an epoxy-type finish to the sheet before attaching it to the building
exterior. Another widely used product is laboratory furniture. Here solid
sheets make very strong and chemically resistant bench-tops. A/C sheet is
also used in fire-protective equipment including wood stove installations.
Corrugated sheet is used primarily in industrial applications including
roofing, siding, and warehouse construction. Warehouses for phosphate ferti-
lizers or other corrosive materials are particularly likely candidates for
A/C corrugated sheets since metal materials would rust and corrode in these
environments.
137
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Special Qualities
The most desirable qualities of asbestos-cement products are their dura-
bility, corrosion resistance, and noncombustibility. Asbestos increases the
strength of the cement product thereby reducing weight. The strength of A/C
in compression is far higher than in tension; as a result several types of
corrugated sheet products have been designed to exploit this property. These
products are extensively employed for roofing and vertical cladding of fac-
tories, industrial buildings, and domestic garages.5 In addition, the mechani-
cal properties of A/C sheet may be further improved by cementing thin sheets
of glass-reinforced plastic on each side of the A/C product.7
Asbestos fibers in A/C sheet products reinforce the cement, protect from
fire, absorb heat from friction, insulate from heat, cold, and sound, insulate
from condensation, and protects from corrosion.5 For fire protection purposes,
A/C sheet has successfully passed appropriate tests to be classified as
noncombustible. The slow rate of heat conduction through A/C materials even
helps retard the spread of fire through structures of which they are a part.
A/C products are therefore versatile, protective, and extremely useful.
SUBSTITUTES
The main competitors to A/C sheet products are:
•
galvanized steel
•
aluminum sheet
•
masonry
•
precast concrete
•
plastics
•
wood
•
asphalt
In building construction, the rot and chemical resistance of A/C sheet
makes it superior to metal since metal corrodes and is subject to rust. How-
ever, metal is cheaper and estimates indicate that in 1979, 15 percent of
the nonresidential building market will use metal wall panels, and perhaps
as much as 40 percent within 10 years.8 These panels of preinsulated steel
are ready to install as walls and are thought to maximize energy efficiency.
Precast concrete is not only more expensive than asbestos, but also in-
volves more costly erection procedures, although this gap is narrowing. For
fume hood use, welded stainless steel is available, but costs more than A/C
sheet. Albarene stone, which mav be a replacement for lab bench tops, is
also more expensive. Impregnated plywood may also be used for lab tops, but
onlv for nonrigid work; to date, A/C sheet is the most cost-effective product
for this use.
138
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Cladding panels are frequently manufactured from glass-reinforced thermo-
setting plastic (GRP). However, these materials do not possess the fire resis-
tance of asbestos cement, and if combustion occurs, toxic fumes may be created.
Thermoplastics, often using acrylic, have also been used for cladding, expecially
1n cases which call for their properties of high transparency. Caution must
be taken in this application, however, as several recent fires, notably in
England, have occurred in buildings using these panels. In such occurrences,
the buildings have been completely lost due to the spread of surface flames
on the panels.9
PVC may also be used in asbestos-cement type roofing applications. The
corrugated, sometimes wire-reinforced form of PVC is applicable to conditions
warranting light transmission, A UV stabilized, f1ame-retardant grade of PVC
is used for this purpose. Metals such as aluminum are also widely used in this
application.10
As has been the case with many other substitutes for asbestos products,
most plastics are more expensive than A/C products, although certain thermo-
plastics may be cost-competitive in specific applications.
Replacement of asbestos fibers in A/C products by an alternative fiber
or filler is currently under investigation by major manufacturers. Potential
alternatives in this case include fiberglass, carbon fibers, and various
natural, synthetic, and mineral fibers.
Perhaps the most promising use of a substitute fiber currently under
investigation is the development of glass-reinforced cement. The common
E-glass fiber, conventionally used in glass-reinforced plastics, cannot be
used for this purpose as the severe alkaline conditions produced during the
setting of Portland cement degrade these glass fibers, with the resultant
composite material losing its favorable mechanical properties. However,
experimentation within the last 10 years has produced a high-zirconia, alkali-
resistant glass fiber, first introduced where the development took place, in
England. The fiber is presently marketed by Pilkington Brothers, Ltd., of
St. Helens, England under the trade name "Cera-FIL."9 It has been found to be
considerably more impact resistant than A/C sheets of comparable strength.
In addition, the "green" boards have wet strength, allowing them to be molded.
Large bore pressure pipes can also be produced from this material. The final
product performs adequately in preventing fire penetration, yet several draw-
backs still remain, including higher price, poor drainage characteristics, and
lack of time-tested durability.
A/C sheet is generally more expensive than corrugated steel, competitive
with aluminum sheets, and less expensive than conventional concrete blocks
and built-up roofing. One of the main selling advantages of A/C sheet,
especially for industrial use, is its resistance to rot, corrosion, and mildew,
along with its fire resistance. ** However, reports indicate that there is
virtually no application in which A/C sheet could not be replaced by a substi-
tute product that is currently on the market, although the cost may be some-
what higher in the use of the alternative product.
139
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MANUFACTURING
Primary Manufacture
A/C sheet and shingles may be made by either a dry, a wet, or a wet
mechanical process. The product is formed, basically, by making a dilute
water slurry of mixed raw ingredients, and then brought to the desired size,
thickness or shape by accumulating the solid materials on a roll while
removing most of the carriage water.6
Dry Process—
In the dry process (Figure 15), plastic bags containing asbestos are
slit and dumped in a mixer. After the necessary additions of cement, silica
and additives, this dry mixture is uniformly distributed onto a flat conveyor
belt, sprayed with water, and then compressed by steel rolls to the thickness
required for the desired product. The raw material make up is a batch
operation with production rates depending on sheet thickness. Fiber intro-
duction occurs 2 to 6 hours per shift.11 This process is especially suited
to the manufacture of shingles and other sheet products.6 As the formed
sheet continuously moves, rotary cutters are used to form the size of sheet
desired or to cut the sheet into shingles. Finally the product is removed
from the conveyor while still in this form and steam cured in an autoclave.
Cut-off saws using diamond or carborundum wheels are then used to trim the
cured sheet to standard size.11 Corrugated sheets may be produced without
the final sanding step that the flat sheets need. The water used to clean the
forming equipment (which is the major source of process water) is normally
collected for clarification and then either recirculated or discarded. Settled
solid material from the clarification can be recycled with any unusable excess
going to landfills.4
Wet Process—
The wet process for making A/C sheets is shown in Figure 16. Here, asbes-
tos fibers are blended with cement and additives as in the dry process, but are
then mixed with water. This slurry mix is in turn introduced into a mold cham-
ber where it is compressed into a dense sheet, forcing out any extra water.6
This material is allowed to harden for 24 to 48 hours. Then air or steam (or
both) is used to cure the final product. The large, thick monolithic sheets
used for such purposes as laboratory bench tops are manufactured by this pro-
cess. Grinding operations used to finish the sheet surfaces often produce
large quantities of dust which may get discharged into the process wastewaters.
As in the dry process, the water from the forming step is clarified and re-
cycled, with the same sludge and wastewater disposal requirements.
One plant visited uses a process similar to this wet process.12 Asbestos
In shipped l«v t ra I n or truck to the plant and stored until use. The plastic-
wrapped asbestos bags are then moved to a mixer where they are hand slit
under a vacuum hood, and dumped into a drv mix of concrete, silica, and, if
color Is necessary, pigment. From this stage, a closed operation mixes this
material, water is added, and the material is pressed in forms to force out
excess water. These sheets, are then air-dried for 3 to 4 days, and depending
140
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WATER
* WASTEWATER
SOLIDS
STEAM
* CONDENSATE
ROLLING
CUTTING
CURING
FINISHING
STORAGE
RAW MATERIALS
STORAGE
PROPORTIONING
DRY MIX
CONSUMER
Figure 15. Asbestos-cement sheet manufacturing operations,
dry process.6
1A1
-------
WATER
#• WASTEWATER
STEAM
^ CONDENSATE
SOLI 0S
PRESS
WET MIX
STORAGE
CURING
HARDENING
FINISHING
RAW MATERIALS
STORAGE
PROPORTIONING
DRY MIX
CONSUMER
Figure 16. Asbestos-cement sheet manufacturing operations,
wet process . 6
142
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upon use, steam cured. The steam-curing process is faster than air curing.
The product 1s subsequentLy sanded by machine (with vacuum hood) to assure
appropriate thicknesses, and machine cut to size. Customer specifications may
be met at this stage for some products; others have secondary or even tertiary
steps where they are cut to even more specific sizes (for example, as in
adapting a sheet to use as a sink hole).
Wot Mechanical Process--
There is a third process used, called a wet mechanical process, for both
A/C sheet and A/C pipe production. This process, shown in Figure 17, is
similar in principle to some papermaking processes. Willowed asbestos is
thoroughly blended with silica, cement, and filler solids in a dry mixer.
These raw materials are then transferred to a wet mixer (or beater). A slurry of
about 97 percent water is formed by adding underflow solids and water from
the savea11 (material being recycled from previous operations). After more
mixing, this slurry is pumped to cylinder vats for deposition onto one or
more horizontal screen cylinders. Water is removed from the underside of
the slurry layer through fine wire mesh screening around the circumferential
surface of each cylinder.6
A layer of A/C material from 0.5 to 2.5 mm thick is produced by the
above process. This is then transferred to an endless felt conveyor so that
a single mat can be built up. Additional water within this matted material
1s removed by a vacuum box prior to transfer of the material to a mandrel or
accumulator roll. This roll winds the mat into a sheet of the desired thick-
ness for the specific product being made. Pressure rollers are used to bond
this mat to stock already deposited on the roll or mandrel and additionally,
to remove excess water. The built-up layer of A/C sheet on the accumulator
roll Is then periodically cut and peeled away. The resultant sheet is suffi-
ciently tough to be handled freely but can nonetheless be molded and shaped.
Afterward, the sheet is passed through a pair of press rollers to shape its
surface and then, depending upon the application, cut into sheet sizes or
shingles. Corrugated sheets may be produced by this method, or flat sheets
can be made bv placing the material on a flat surface for curing. The
asbestos-containing water from this slurry is recycled to the ongoing process,
so that very little asbestos is thought to be lost from the operation.
Methods such as cylinder showers are used by manufacturers to ensure
satisfactory operation of this process sequence. Both the cylinder screen
and the felt conveyor are kept clf^an by this method in which water is sprayed
on the screen surface each time the mat is removed by the felt.6 Cement or
fiber particles caught in the holes of the screen are washed out to prevent
"blinding." Acetic or hydrochloric acid is also used upon occasion to remove
cement deposits from the cylinders, mandrels, and accumulator rolls. This may
take plare while the machine is in operation. Cylinder screens are also easily
removed for separate washing. Felt washing showers are used to wash fibers out
of the felt after the mat of fiber product has been picked up by the mandrel
or accumulation rolls. This row of high-pressure nozzles, aided by a "whipper"
can control fiber buildup in the felt, which in turn could prevent vacuum
boxes from removing the excess water from the mat, an indespensible part of
the manufacturing process.
143
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RAW MATERIALS
STORAGE
PROPORTIONING
ORY MIX
RECYCLED SOLIDS
WATER
RECYCLED WATER
~ WASTEWATER
* SLUDGE
STEAM
CONDENSATE
SOLIDS
WET MIX
FORMING
F IN ISHING
STORAGE
CUTTING
CLARIFICATION
(SAVE-ALL)
CURING
AIR/AUTOCLAVE
CONSUMER
Figure 17. Asbestos-cement sheet manufacturing operations,
wet mechanical process.6
144
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Secondary Manufacture
Tliere is some secondary manufacture of A/C sh«et products consisting
mainly of central fabricating shops which cut and shape the material to
specific sizes. This may involve sawing, trimming, drilling, or grinding
and may be done as part of field fabrications also. Flat asbestos sheets
used on homes, barns, <>r other inexpensive construction are usually installed
with fasteners or nails and require little drilling. With A/C products that
do require field fabrication, knives or saws may be used, as well as drills;
however, EPA has found that dust-collection devices are usually installed on
such equipment, so major emissions of asbestos particles to the air do not
occur.13 The amount of dust generated by central fabrication shops working
on A/C building products is estimated at about 90 kg/wk (200 lb/wk).1* This
corresponds to 4717 kg/yr (10,400 lb/yr) going to landfills or dumps. About
18 percent or less than 1 ton of this is thought to be asbestos.
Many A/C sheets come out of the original manufacturing sites ready for
use. However, as described above, others require additional work before being
ready for sale to consumers. These may go from the manufacturer to a
distributor to, say, a furniture manufacturer, and finally to a company buying
laboratory furniture, before the company at the end of the line receives the
products. The intermediary steps may involve cutting or drilling but the
final purchase of the product is in ready-to-use form.
Manufacturing Plants
Table 36 gives the locations of the five major manufacturers of A/C sheet,
in the next section, Asbestos Release, both the pollution control processes
seen at one plant visited and possible control measures used by the other
manufacturers listed will be discussed. This includes emissions to air, land,
and water, and all pollutant control and health protection measures taken.
TABLE 36. MAJOR MANUFACTURERS OF ASBESTOS-CEMENT SHEET
6 • 1 ¦» » 1 5
Manufacturer
Location
A/C products
Johns-Manville
International Building
Products, Inc.c
Supradur Mfg.
Nicolet Inc.
A/C sheet (flat)^
A/C sheet (flat)
New Orleans, LA A/C sheet (corrugated)
Waukegan, IL
Nashua, NH
Wind Gap, PA
Ambler, PA
A/C sheet (flat and corrugated)
A/C shingles (roofing and siding)
A/C sheet (flat)
Products other than those mentioned may also be manufactured at these sites.
A/C sheet produced at this plant may undergo job site fabrication in-house
to a greater extent than that product originating from Nashua.
"Operation used to be owned by Gold Bond Building Products, a Division of
National Gypsum. (Asbestos Magazine, March 1981, p. 32).
145
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Production Volume
Production volumes are not known, although it is known that 7,900 metric
tons (8,690 short tons) of asbestos was used in 1980 for the production of all
types of A/C sheet products.1 Chrysotile asbestos was the predominant fiber
used, along with a small amount of amosite.1
ASBESTOS RELEASE
Input-Output
Figure 18 shows estimated process disposal and emissions for asbestos
cement manufacturing based on Levine's16 1974 estimates projected to 1980 U.S.
Bureau of Mines1 consumption figures. Of the 7,900 metric tons entering the
process a3 raw asbestos fiber, approximately 7,699 metric tons are incor-
porated into the product and 198 metric tons are sent to disposal as product
scrap, clarifier sludge, and vacuum cleaner and baghouse dust. An estimated
0.8 metric tons escape through a control device (typically a baghouse) and
1.8 metric tons are discharged to water. Levine's emission estimates are
based on gross assumptions with a reported uncertainty of at least an order
of magnitude. Meylan** reports emissions of 1 to 3 orders of magnitude less.
Atmospheric emissions from disposal are shown to be 0.4 metric tons. This
last estimate, which follows Levine's16 1974 data, also takes into account the
Asbestos NESHAPs regulation adopted in 1975 regarding the disposal of asbestos-
containing waste material.
During Manufacture
Workplace Exposure—
As shown in Table 37, exposure to airborne asbestos fibers during A/C
sheet manufacturing varies greatly within and between processing steps. A
typical exposure for most operations is 2.0 fibers/cc TWA.16 Table 37 also
presents the lowered fiber counts that may be possible if best available
technology (BAT) steps are taken (hoods, ventilation, proper bag handling,
etc.). The model site visited had initiated such controls. It is also in-
teresting to note here that the TWA fiber counts at the fiber introduction
and dry mix steps for the A/C sheet process are higher than for the same
process for A/C pipe, as fiber is introduced more directly for A/C sheet.11
The fiber counts (0.3 to 8.7 f/cc) at this stage represent the highest in the
manufacturing steps for A/C sheet. The highest typical fiber count (3.0 f/cc),
however, occurs during sheet sanding. Although control equipment has proven
effective here, it is difficult to control fiber loss from the large surface
areas of the sheet during sanding, and loose fibers remaining on the sheet
tend to become airborne as the material is handled.11
Emissions to Air—
Asbestos release to the atmosphere may come both from baghouse emissions
and disposal emissions. Actual measurements of the asbestos fiber concentra-
tion in the vicinity of an asbestos cement sheet manufacturer are very limited.
However, Suta and Levine16 estimated concentrations near asbestos industrial
146
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MANUFACTURING OPERATIONS
RECEIVING
AND
STORAGE
CURING
CONSUMER
VACUUMED
OUST
LEGEND
CLARIFIER
BAGHOUSE
INPUT/OUTPUT
.MANUFACTURING
PROCESSES
BAGHOUSE
EMISSIONS
c.8 tpy
CONTROL EQUIPMENT
ULTIMATE DEPOSITION
SLUDGE ^
LAND
DlSPOSAL
WATER
EMISSIONS
EMISSIONS
DISPOSAL
EMISSIONS
0. <4 TPY
TPY
Figure 18. Input/output of asbestos in the asbestos cement industry (metric tons).
-------
TABLE 37. MEASURED TIME-WEIGHTED AVERAGE FIBER COUNTS DURING
THE MANUFACTURE OF ASBESTOS-CEMENT SH£ETa*b11
Process step
Fiber count with
existing control
technology
Typical Range
Fibers/cc Fibers/cc
Fiber count with
best available
technology0
Fibers/cc
1
Receiving & storage
1.0
0.25-2.5
0.5 or 1.0
2
Fiber introduction
2.3
0.3-8.7
1.0
3
Dry mix
2.5
1.1-8.4
1.5
4
Wet mix
1.25
_
0.9
5
Sheet formation
2.0
1.6-3.5
1.25
6
Dry/cure
1.9
1.3-2.5
1.25
7
Cut/trim
2.5
0.6-6.7
1.0
H
Sand
3.0
0.9-8.0
2.0
9
Finishing & fabrication
1.8
0.9-3.6
1.0
Optical-microscope-visible fibers, 5 yni long or longer.
Data Base: Data collected from plants consuming 89 percent of the
asbestos used for A/C aheet production.
"Projected fiber counts are estimates of average exposure after
implementing BAT. Variations of these values are expected de-
pending upon individual installations.
148
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facilities using mathematically derived dispersion curves of assumed plant
emissions. In the case of asbestos cement, it wa3 estimated that a population
within 5 km of a manufacturing plant would be exposed to a median atmospheric
asbestos concentration of 27.0 and 7.2 ng/m3 for urban and rural facilities,
respectively. Comparing this data with the median U.S. atmospheric asbestos
fiber concentration (20 ng/m3), it appears that asbestos cement manufacturing
contributes little to nonoccupational exposure. However, actual ambient moni-
toring in the vicinity of an asbestos cement sheet facility is necessary to
confirm Suta and Levine's estimates.
Release to Water—
Water usage in A/C sheet plants ranges from 280 to 2,040 cubic meters per
day.6 This varies not only from plant to plant, but within a particular plant,
depending upon cement type and other variables needed to make the product the
oorrect consistency. A minimal effluent volume from a plant was found to be
7.5 cubic meters per metric ton (1,800 gal/ton) of production. Using Levine's16
1974 estimates of release to water scaled to 1980 asbestos consumption figures
as reported by the U.S. Bureau of Mines,1 it is estimated that annual asbestos
release to water for the entire asbestos cement sheet industry is 1.8 metric
tons.
A/C plants recycle most of the water they use, which serves as a recovery
method for all usable solids contained in their wastewater. After leaving the
machine vat, this water (which is 80 to 90 percent of all the water used in
the A/C process) passes through a save-all where solids settle to the bottom,
later to be pumped to the wet mixer to become part of the slurry therein.6
If the save-all is efficient, much of the water it clarifies can be used for
such purposes as showers, dilution, etc. Any overflow from the save-all can
be discharged from the plant or treated and returned to the plant to be used
as its quality justifies. Uses for such water may include water needed for
vacuum seals, wet saws, cooling, hvdrotesting, or plant start-up. If the
treated water cannot serve in these uses, fresh water must be used in its
place. The quality and temperature of save-all overflow water is rarely
acceptable without additional clarification.6
At least one A/C sheet plant is known to completely recirculate the water
it uses. Benefits of such a system include reduced water cost, reduced sewer
service charges, minimal asbestos loss, and in addition, a reportedly stronger
product. The ma)or problem encountered in complete water recycling at a plant
Is scaling.6 As spray nozzles build up with mineral deposits, they require
occasional unplugging. Water lines are regularly scored with a pneumatically
driven cleaner, with the introduction of fine sand to the pumps to help elimi-
nate deposits. While this system works in a study plant, it is not known if
the same measures would work in plants producing sheet products that have more
stringent quality specifications. However, current progress indicates that
complete water recirculation systems such as this are realistic future goals.
For example, one plant studied used a completely closed loop circulation
system for all the water used. In an enclosed setting tank, beneath the
plant, the water is continuously cleaned and reused. The filtered solids are
pelletized and placed in a landfill. As the asbestos fibers are hound In
cement, wrapping is not even necessary before thev are disposed of in this
manner.
149
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Release to Land—
Estimates indicate that 5 to 10 percent of all A/C products (A/C sheet,
A/C pipe, etc.) are dumped as scrap.6 Of this, 10 percent is thought to be
fine dust from baghouse collections and 90 percent is coarse scrap from trim-
mings and breakage from products that fail quality assurance tests.b Bag-
house emissions are generally pelletized at the plant to transform free fibers
into tightly bound balls of cement. Since the asbestos shipped to a landfill
la encapsulated in cement, emissions to air or water is minimal.
Most worn out asbestos cement sheet is probably disposed of in landfills.
As in the case of manufacturing wastes, the worn out material is encapsulated
in the cement matrix, resulting in minimal release to water or air.
Quantities of solids associated with treatment and control of wastewater
from A/C product manufacture are of significant volume, especially when com-
pared to the small volume coming from paper millboard, roofing, and floor
tile manufacturing. However, even though losses to solid wastes may be great,
the loss of asbestos fibers themselves is thought to be minimal (1 percent or
less).6 The fiber content of the waste solids is low, which is why they have
no salvage or recovery value.
During Use
Loss of asbestos fibers during installation and laying of A/C sheet
materials is not considered to be significant, as the asbestos fibers are
encased by asphalt or cement. Field fabrication of A/C sheet can release
some dust during fitting, cutting, drilling, or grinding operations; but it
has been found that emission control devices, such as bags to collect dust,
are usually used in the field when such operations take place, and further,
that cutting and fitting processes are more often carried out by central
fabricating shops (secondary producers). If there are no adequate control
measures, exposure within such shops could be high. As before, the scrap
materials from cutting operations end up in dumps and landfills.1* The
amount of dust generated by central fabrication operations for all A/C
building products is estimated to be 90 kg/wk (200 lb/wk), or 4,717 kg/wk
(10,400 lb/yr).4 If the asbestos content of this dust is 18 percent, slightly
less than 1 ton/yr is generated by such shops. A/C sheets are primarily
installed in industrial buildings, warehouses, and to a more limited degree,
residential applications. Flat asbestos sheets used in homes, barns or other
more expensive construction, are usually installed with fasteners or nails,
requiring only minimal drilling, if any. If adjusted in the field, these are
usually cut with knives or saws.
The probable asbestos dust concentrations at the actual construction site
where A/C sheet (and/or pipe) is being used, range from less than 2 fibers/cc
to as high as 20 fibers/cc.16 Concentrations from both machine drilling and
machine sawing (using effective exhaust ventilation in the field, as mentioned
above) fall towards the lower end, indicating emissions of less than 2 fibers/cc
of probable asbestos fiber. Concentrations from hand sawing range from 2 to 4
fibers/cc and machine sawing (without controls) with a jigsaw from 2 to 10
fibers/cc, rising to 10 to 20 fibers/cc using a circular saw, the highest level
for the A/C sheet category. For comparison, the asbestos dust concentrations
150
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from use of a circular saw on insulation board (also without effective
ventiLation) range from 20 flbers/cc upwards, and spraying of asbestos,
extensively uaed in past applications, is thought to expose over 100 fibers/
cc.1G
Considering that an estimated 1.13 x 106 Mt of A/C sheet is in place,
estimates indicate that 1,130 Mt/yr of asbestos fibers may be released.16
This figure excludes roofing uses, which would perhaps double the estimate.
Weathering and wear rates are expected to be low, roughly 0.1 percent per
year of the installed tonnage mentioned above. No free asbestos fibers are
expected to be emitted from A/C sheet products that are not exposed to weather
or corrosive materials; asbestos released, if any, would be bound in the
cement matrix. A/C sheets used in the construction of warehouses and bulk
storage for corrosive materials and fertilizers may release asbestos fibers
jf the cement contained in the binder material disintegrates due to the
corrosive atmosphere. However, asbestos is used in this product specifically
for this reason—it provides resistance from corrosion. Figures for such
asbestos tonnage Installed in corrosive atmospheres are not currently
available.
High concentrations (up to 543 million fibers per liter) of waterbome
asbestos have been reported for drinking water collected in cisterns receiving
runoff from asbestos-tile type roofing materials.17 Insignificant waterbome
asbestos concentrations, however, were found in cisterns receiving water from
the more typical asphalt-asbestos roofing shingles. Seemingly, the asphalt
binds the fibers well enough to prevent significant fiber release.17
During Disposal
A/C sheets are thought to have a life expectancy of about 15 to 25 years
before being replaced by new materials. However, life expectancy varies with
product. Laboratory table tops last until the building of which they are a
part is torn down, as do the textured A/C sheets used in architectural con-
struction. Flat sheet pieces have a more practical lifetime, wearing out
as the products they are part of (arc shields, welding tables) require re-
pi a cement. A/C roofing shingles are thought to last 20 to 25 years.
If 75 percent of all annual production really is used for replacement
purposes, 187,000 tons of A/C sheet products are replaced each year (this
number includes roofing applications but does not consider weathering effects)
representing about 34,000 tons of asbestos. Most worn out sheet is probably
dumped in landfills.
CONCLUSION
The growth in the market for A/C sheet products in the U.S. has lagged
behind that of the construction industry in general in recent years. ** Although
the present market for corrugated sheet is stable and projected to remain so,
the flat sheet market has declined, with future decreases predicted. Growth
in this area is only a few percent per year. Competitive pressures from alter-
native products, along with increasing concern about asbestos fiber exposure
151
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from both contractors and homeowners have contributed to the slight market
decreases. For construction purposes, A/C sheet is now more often used only
when its specific properties are needed.
Currently, there is a growing Interest in substitutes for A/C sheet.
Representatives of companies either manufacturing substitute cement sheet
or planning to make asbestos-free cement sheet products report an increased
interest from other parties using or requiring A/C sheet products.19-21
Alternatives include the manufacture of flat glass-reinforced concrete sheets
that can be produced at competitive prices.20 Cement/wood board could also
be formed into textured siding and roofing shingles that, if produced, could
compete effectively with A/C roofing and siding shingles.22 Aluminum vinyl
siding is reportedly forcing A/C siding from the residential market except
where special fire protection is required or where slate-like appearance is
desired.2 3
No material that can adequately match A/C sheet's qualities as a lab
table is available, though other products are currently used. (Slate is one
of the materials used here but it is inordinately expensive.) At this time
no single material could replace ebonized asbestos sheet in all electrical
applications, but Benelex®, a laminated hardboard product manufactured by
Masonite Corporation, Laurel, Mississippi, has been shown to be a usable
substitute for some.2^
Asbestos-cement sheet still stands as a versatile, all-purpose material
that is relied upon for its excellent durability, heat resistance, work-
ability, and relatively low cost. This unique combination of qualities has
until now given it an unrivaled niche in various markets in the United States.
While no single product matches A/C sheet's qualities exactly (companies
such as Johns Manville claim that all nonasbestos sheets degrade more rapidly
than asbestos), there are products that can be identified as suitable sub-
stitutes for A/C sheet for most applications. With new replacements, some
recognition of the performance requirements of the end use has to be clarified
with the user; such requirements have often been neglected in favor of the
ease of A/C in that the decision has been made in the past. However, with
properly defined requirements, many of these substitute products can adequately
fulfill uses delegated to asbestos in the past, even though this may require
a certain amount of testing and design work to come up with the right thickness
and formulation to make the alternative product work. Most substitutes are
currently more expensive than A/C but the differential is shrinking.
152
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REFERENCES
1. Clifton, R. A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of
Mines, Washington, D.C.
2. U.S. Bureau of Mines. Mineral Commodity Profiles: Asbestos. July 1979.
3. U.S. Bureau of the Census, 1977 Census of Manufacturers.
4. Meylau, W. M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination.
Task III - Asbestos. EPA 560/6-78-005. August 1978.
5. Bradfield, R. F. N. Asbestos: Review of Uses, Health Effects, Measure-
ment and Control. Atkins Research and Development, Epsom Surrey,
England. January 1977.
6. Carton, R. J. Development Document for Effluent Limitation Guidelines
and New Source Performance Standards for Building, Construction, and
Paper Segments of the Asbestos Manufacturing Point Source Category.
U.S. Environmental Protection Agency. EPA-440/l-74-017a. February 1974.
7. DeKany, J. P. Economic Impact Assessment for the Proposed Revisions to
the Occupational Exposure Standards for Asbestos Dust. OSHA, 1979.
8. Pre-lnsulated Panels Maximize Energy Efficiency, Electr. Comf. Cond.
News, Vol. 6, No. 1, p. 19-20. Jan. 1979.
9. Fabbrocino, V., and E. R. Ermolli. Hybrid Composites in an A/C and
Glass-Reinforced Plastic, Ingegnere, Italy, Vol. 51, No. 10, p. 417-27.
October 1976.
10. Pye, A. M. A Review of Asbestos Substitute Materials in Industrial
Applications, Journal of Hazardous Materials, Vol. 3, p. 125-147.
1979.
11. 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.
12. Roy, N. Final Trip Report to Johns-Manville Corporation, A/C Plant in
Nashua, N.H. GCA/Technology Division, Bedford, MA. October 23, 1979.
153
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13. U.S. Environmental Protection Agency, 1974. Background Information on
National Emission Standards for Hazardous Air Pollutants: Proposed
Amendments. Research Triangle Park, N.C.
14. W. E. Davis and Assoc. (Leawood, KS). National Inventory of Sources and
Emissions: Asbestos - 1968. U.S. Environmental Protection Agency.
Office of Air and Water Programs OAQPS, Research Triangle Park, N.C.
APTD-70, February 1970.
15. Telecon. E. Fenner. J/M Corporation, Denver, CO with N. Roy, GCA/
Technology Division. October 24, 1979.
16. Levine, R., (ed.). Asbestos: An Information Resource. DHEW Publication
Number (NIH) 79-1681, U.S. Department of Health, Education and Welfare,
National Cancer Institute, Public Health Service, Bethesda, Maryland,
May 1978.
17. U.S. Environmental Protection Agency. Exposure to Asbestos from Drinking
Water in the U.S. EPA-600/1-79-028. August 1979.
18. Suta, B. E, and R. J. Levine. Non-Occupational Asbestos Emissions and
Exposures. Asbestos, Properties, Applications and Hazards. Volume 1.
John Wiley and Sons, New York, N.Y. 1979.
19. Telecon. J. Jones, Assistant General Manaber, CEM-FIL Corp., Nashville,
Tennessee, with S. Duletsky, GCA/Technology Division, January 31, 1980.
20. Telecon. W. H. Lewis, GRC Products, Inc., Schertz, Texas, with
S. Duletsky, GCA/Technology Division, February 11, 1980.
21. Telecon. J. Bostian, Asbestos Fabricators, Inc., Charlotte, North
Carolina, with S. Duletsky, GCA/Technology Division, March 7, 1980.
22. international Housing Corporation. Notebook Containing Information
About Cement/Wood Board. Sacramento, California. 1979.
23. Masonite Corporation. Siding: 1980. Form 902180. Towanda, Pennsyl-
vania. 20 pages.
24. Krusell, N., and D. Cogley. Asbestos Substitute Performance Analysis.
Prepared by GCA/Technology Division, Bedford, Mass., for Office of
Pesticides and Toxic Substances, U.S. Environmental Protection Agency,
Washington, D.C. May 1981. EPA Contract No. 68-02-3168.
154
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SECTION 8
FLOORING PRODUCTS
INTRODUCTION
The fourth largest industrial use of asbestos fiber is the manufacture
of floor tile. Approximately 10 percent of all asbestos consumed in the United
States in 1980 was used in the manufacture of floor tile. This industry
produces two major product lines utilizing asbestos. The vast majority of
asbestos (up to 95 percent) is used in the production of vinyl-asbestos floor
tile while the remainder is used to produce asphalt floor tiles.1 Both types
of tile have been used extensively in commercial and industrial applications
as well as in homes and offices. Asbestos tile utilizes the shortest chrysotile
asbestos fibers (grades 5 through 7) to impart strength, dimensional stability
and resistance to cold. In addition, the asbestos fibers perform an important
function in giving the polymer sheets "wet-strength" during the manufacturing
process.1 The production of both vinyl-asbestos and asphalt tile is similar,
involving batch blending of ingredients in Banbury mixers followed by contin-
uous tile sheet forming using mills and calenders. The production processes
differ basically in that higher temperatures are needed to flux and process
vinyl copolymer.2
PRODUCT DESCRIPTION
Composition
Only the chrysotile form of asbestos is used in tile production, with
1980 usage amounting to approximately 36,080 metric tons.3 A typical for-
mulation of vinyl-asbestos floor tile1* indicates the composition shown in
Table 38.
While specific ingredient formulas vary with manufacturer and the type
of tile, the asbestos content of the tile ranges from 8 to 30 percent by
weight,5 or up to 0.64 kilograms of asbestos per square meter of tile.6 Al-
though exact percentages are not available, most manufacturers have indicated
an asbestos content in the lower end of this range while one manufacturer has
indicated the asbestos content to be significantly less than 8 percent.7
Actual tile formulations demonstrate a range of weight percentages of
these individual constituents. PVC resin serves as the binder and makes up
from 15 to 25 percent of the tile. Chemical stabilizers usually vary little
155
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from 1 percent of the total formulation. Limestone and other fillers repre-
sent AO to 70 percent of the weight, while pigment content usually averages
about 5 percent, but may vary widely depending upon the materials required
to produce the desired color.8
TABLE 38. FORMULATION FOR A VINYL-ASBESTOS FLOOR TILE9
Material Percent by weight
Vinyl chloride-vinyl acetate copolymer 15
Extender resin 2
Phthalate esters (plasticizer) 5
Extender plasticizer 1
Epoxidized soybean oil 1
Stabilizer 1
Asbestos short 7R fibers 28
Limestone filler 43
Pigment 4
The tile is typically produced in 9 x 9 inch or 12 x 12 inch sizes,
with thicknesses varying from 1/32 to 3/32 inches. A large volume of vinyl-
asbestos tile is embossed and simultaneously valley printed with a wide and
attractive array of designs, to enhance its appearance.9
Uses and Applications
Asbestos flooring is used for protective and decorative covering of floors
in industrial, commercial, and residential applications. In the early 1970's
asbestos flooring comprised approximately 20 percent of the total flooring
market. The use of asbestos in flooring has since decreased due to an increase
in popularity of other types of flooring.1 However, it still commands a high
percentage share of the resilient floor covering market.
Vinyl-asbestos floor tiles and sheet vinyl flooring may be installed on
concrete, prepared wood floors or over old tile floors. Chief competitors
include ceramic tile, brick, stone, wood, terrazo, and carpet.
Special Qualities
Asbestos is used in flooring products because of its structural properties,
which aid not only in creating an efficient covering but also in the manu-
facture of the tile and sheet products themselves. Asbestos fibers provide
durability, resilience, flexibility, dimensional stability, moisture resis-
tance, chemical and fire resistance, and indentation strength. In the manu-
facturing process, asbestos contributes to the mill tack, or adherence to
the roll mills in production; it also provides heat resistance necessary for
156
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i-rocesaing as one continuous sheet and dimensional stability to prevent ex-
pansion or shrinkage during production.
SUBSTITUTES
Substitutes for asbestos fibers are currently being researched for pos-
sible use in the production of vinyl and asphalt tile. Potential substitutes
Include glass fiber, sintered metal, steel wool, mineral wool, carbon fibers
and cellulose fibers. All of these products lack the overall structural and
thermal qualities of asbestos at comparable prices. The Monsanto Company
has developed Santoweb®, a natural cellulose fiber substitute for asbestos in
floor tile.10 Cost is considered to be the major barrier to use of Santoweb.
The Armstrong Cork Company offers an asbestos-free vinyl floor tile.11
in which the limestone content is increased to replace the asbestos. The
limestone alone is not sufficient to maintain all of the tile's desired
qualities, such as durability. It is also necessary to increase the plastic
binder content to meet these goals. These tiles meet the certification re-
quirements for fire resistance, durability, dimensional stability and resil-
ience as specified by several government agencies. The tile costs about 25
to 50 percent more than its asbestos counterpart. For this reason it is
better suited to the residential replacement market, as opposed to large
commercial installations. Coated types of vinyl flooring (plastisol-coated
felts) are another relatively new type of flooring which is beginning to
capture a portion of the vinyl-asbestos market. Non-asbestos flooring is
specified for some resilient flooring installations and non-asbestos products
now comprise between 5 and 10 percent of the resilient flooring market.12
MANUFACTURING
Primary Manufacture
Asbestos floor tile is manufactured by a process represented schematically
In Figure 19. While each individual manufacturer employs a proprietary prod-
uction line process geared to his specific product, the general flow of raw
and finished materials in the industry is similar.
Asbestos fibers arrive by truck and railroad at most facilities in 50,
70, and 100-pound polyethylene plastic bags which are stacked on wooden
pallets. Forklift trucks transport the pallets to a storage area where they
are stacked up to four pallets high. Bags are inspected upon delivery and
tears are immediately taped. Often the entire pallet is shrink-wrapped with
an additional plastic wrapping. Asbestos is sometimes shipped in pressure-
packed bags in which the asbestos is pressed into a hard consolidated mass.
Asbestos can also be pressed into small pellets and can then be shipped
either in bulk quantities or bagged. One flooring company receives 75 per-
cent of its asbestos in bagged, pelletized form.*1* Fibers in pelletized form
157
1
-------
RAW ASBESTOS FIBER
WATER
COOL
COOLING
BROKEN
FRAME
STRAP
WASTEWATER
WATER
FRAME
STRAP
COOLING WATER
COOLING
WASTEWATER
WATER
CHIP MOTTLER
BUFFER
OIL MOTTLER
RADIANT HEATER
PACKAGING
VIBRATOR
PUNCH PRESS
CALENDER ROLLS(H
SCRAP(H
BREAKER
HIGH SHEAR(H)
MIXER
COOLING CHAMBER
COOLING CHAMBER
RECEIVING
ANO
STORAGE
BLENDING OF ASBESTOS(H)
FIBER S OTHER RAW MATERIALS
CONSUMER
NOTE; (H) indicates hooded operations.
Figure 19. Floor tile manufacturing operation.13
158
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and in pressure-packed bags are less likely to leak and those which do leak
are less likely to become airborne.13
Pneumatic corveying systems are used to transport pelletized asbestos
from railway cars and trailers to intermediate or primary storage bins.
From storage, the pallets are transported to the fiber introduction area.
Here, when possible, an entire bag of asbestos fiber is added unopened, to a
batch mix. The plastic bag is incorporated into the product. Plant personnel
at one facility indicated that approximately 55 percent of batch mixes utilize
entire bags while the remaining mixes require that a bag be manually opened
and the asbestos libers weighed to predetermined mix requirements.1k Automatic
bag openers are available, but are in most cases not practical in the flooring
industry due to the relatively small batches used. However, automatic bag
openers would reduce worker exposure by increasing the physical distance be-
tween workers and asbestos.
Ingredients for tile production, including raw asbestos fiber, pigment,
and fillers are weighed and mixed dry in a Banbury mixer (high shear mixer).
The mixer works the dry materials into an agglomerated plastic mass. As the
material is sheared in the Banbury, the asbestos, fillers, and pigments are
dispersed throughout the vinyl mass. Liquid constituents, if required, are
then added and thoroughly blended into the batch. While the mechanical
working of the material itself generates heat, more heat may be added, if
required, to raise the batch temperature to 300°F (150°C) and flux the polymer
resin. The warm plastic mass is then fed to a mill where it is joined with
recycled scrap and undergoes final mixing. From thi9 point on, the process
is continuous. The mill consists of a series of hot rollers (calender rolls)
that squeeze the mass of raw tile material down to a desired thickness.
During the milling operation, surface decoration in the form of small colored
chips of tile (mottle) may be sprinkled onto the surface of the raw tile
sheet and pressed in to become a part of the sheet. Some tile has a surface
decoration embossed and fused into the tile surface during the rolling oper-
ation. After milling, the tile passes through calenders until it reaches the
required final thickness and is ready for cooling. Tile cooling is accom-
plished in many ways and a given tile plant may use one or several methods.
Direct water contact in which the tile is immersed in, or sprayed by water is
one method. Indirect water cooling utilizing water-filled rollers is another.
Some plants pass the tile through a refrigeration unit to cool the tile sur-
face. After cooling, the tile is waxed, stamped into squares, inspected, and
packaged. Trimmings and rejected tile squares are chopped up and reused.1
Asbestos in the floor tile is thought to be completely encapsulated when it is
shipped. Only mechanical action, such as additional cutting and shaping by
wholesalers, retailers, and installers will liberate the individual asbestos
fibers from the floor tile after it is shipped.
Sheet vinyl flooring (flooring carrier, flooring felt) is an asbestos
paper product which forms the underlayer of sheet vinyl flooring. The backing
is produced on a paper machine, following production techniques outlined in
Section A of this report. During manufacture, the asbestos fibers are coated
with latex and are reported to be fully encapsulated when the sheet backing
159
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is readied for use in the manufacture of sheet vinyl flooring. The major
steps in the manufacture oL sheet vinyl flooring are coating, printing, fusion,
trimming and packaging. The flooring may be manufactured in the same plant
as the sheet backing or in a separate facility.
Production of sheet vinyl flooring begins with a coating operation. Here
the sheet backing is coated with a latex and/or plastisol coating. These
coats are applied by reverse roll coaters or blade coaters. Once the coatings
are applied, the sheet is passed through an oven where these layers are dried
and jelled. The coated sheet is then transported to a printing operation
where one or more engraved cylinders transfer designs to the coated sheet.
In some cases, there will be several printing stations which separately apply
one color or aspect of the design patterns. The printed sheet then goes to a
fusion step where the sheet is coated with another layer of material called
the "wearlayer." The wearlayer is a homogeneous polymer application that
provides an impervious surface for the finished product. The coated and
printed sheet is next fed through an oven where the backing itself, the layers
of latex and plastisol and the wearlayer are fused into a single product.
After fusion, these layers remain distinct but are no longer chemically or
mechanically separable. The vinyl sheet is then cooled, cut to size, packed
and shipped.
Manufacturing Plants
The major asbestos floor tile manufacturers and their plant locations
are presented in Table 39. Actual plant-by-plant asbestos use was unavailable
as manufacturers regard this information as confidential. The asbestos con-
tent of the finished floor tile is also kept confidential, precluding the
establishment of "typical" asbestos use and emission rates. As the manufac-
turers sell floor tile directly to retailers, lumber yards, etc., there are
no secondary fabricators in this industry.
TABLE 39. MAJOR U.S. MANUFACTURERS OF ASBESTOS
FLOORING1 »15
Plane location
Manufacturer
Vinyl asbestos tile
Sheet backing
American Blltrlte, Inc. Trenton* New Jersey
Amtlco Flooring Division
Norwood* Massachusetts
Armstrong Cork Co.
South Gate, California Pulton, Nttr York
Kankakee, Illinois
Jackson, Mississippi
Lancaster. Pennsylvania
Congoleum Corporation
Resilient Flooring
Division
Cedarhuret, Maryland
CAP Corporation
Consmer Products Group
Long Beach, California Whitehall. Pennsylvania
Valla Gate, New York
Kentlie Floors
Brooklyn* New York
Chicago, Illinois
Mannlngton Hllla, Inc. Salea, New Jersey
Uvalde Rock Asphalt
Azrock Floor Products
Division
Houston, Texas
160
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Production Volumes
The principal forma of resilient flooring used include vinyl-asbeatos,
asphalt-asbestos and solid vinyl. In 1975 asbestos flooring accounted for
approximately 91 percent of the resilient floor covering market.1* Of this
total, 38 percent was floor tile and 53 percent was sheet flooring. Only 9
percent of the resilient floor covering market was held by nonasbestos-
containing products. The manufacture of linoleum, another type of resilient
flooring, was discontinued in 1974 due to competition with vinyl floorings.12
Asbestos flooring competes principally with carpeting and solid vinyl flooring.
This figure has decreased primarily due to the growing popularity of carpeting,
especially the use of tufted carpets in both residential and commercial
buildings. From 1971 to 1980 the use of asbestos in flooring decreased by
about 48 percent with asbestos use in flooring decreasing from 173,000 metric
tons to 90,020 metric tons. The market share of all forms of vinyl flooring
is now believed to be well established and is not expected to change signifi-
cantly in the foreseeable future.12 Carpeting is expected to fulfill any
increased demand for flooring.
Tile is typically replaced before it completely wears out for reasons
of style and decoration. A large percentage of production, estimated to be
from 40 to 60 percent,1 is therefore intended as flooring replacement.
ASBESTOS RELEASE
Atmospheric emission of asbestos fiber and asbestos-bearing scrap from
the production of asbestos tile can be in the form of air, water, and solid
waste discharges. These discharges are not completely independent as fibers
collected in a control device limiting air emissions must be handled as a
solid waste, and some solid waste is ultimately disposed of through incin-
eration which may re-release the asbestos to the air. While few data are
available on individual plant emissions, estimates have been made on total
industry discharges and these will be discussed. In addition, those process
points within a facility where the asbestos may be released to the atmosphere
will be examined and available data, such as worker exposure levels, will be
presented. Asbestos emissions due to product end use will be included when
available.
Input/Output
Figure 20 shows estimates of process and disposal emissions for the as-
bestos floor tile manufacturing industry. These figures are based on
Levine's16 1974 estimates projected to 1980 U.S. Bureau of Mines3 consump-
tion figures.* Of the 36,080 metric tons of raw fiber entering the process,
approximately 35,135 m.t. are incorporated into the product and 945 m.t.
GCA emission and cumulative exposure estimates are computed on the assumption
that vinyl-asbestos floor tile constitutes 40 percent of the asbestos usage
for asbestos-containing flooring products with the remaining 60 percent going
to manufacture of sheet vinyl-flooring and flooring felt. These latter
products are discussed in Section 4, Paper Products.
161
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KAMUFACmiHC OPtMTIONS
to
*kei*iks
(UU
MiESTOS
FIIEI
STORAGE
34,080 re*
BAGH0U5E
USEND
RAGHOUSE ! CATCH
j * tp*
LAKO
DISPOSAL
DISPOSAL
ehTssiohs
2 TPY
VACUUMS
CM.CWCR
SCMP
ROLLS
•RUMtl
CMSWtCk
JS.1J5 w
935 TPy
fi TPY
Inpvt/outout
j | - iMxufuctvriny op«r«tlom
- control cquipntflt
- ulti»lte deposition
- tolids
- Mt«r
- »lf
Figure 20, Process and disposal emissions (in metric tons) vinyl-asbestos floor tile industry.
-------
are sent to disposal as vacuum cleaner and baghouse dust. An estimated 4
metric tons escape through a control device (typically a baghouse). Levine's16
atmospheric emissions estimates are based on gross assumptions with a re-
ported uncertainty of at least an order of magnitude. Meylan's1 estimates of
emissions are generally 1 to 3 orders of magnitude lower. Atmospheric emis-
sions from disposal, based on GCA estimates* are shown to total 2 metric tons
per year for the floor tile industry. This estimation is loosely based on
Levine's 1974 data and takes into account new regulations adopted in 1975
regarding the disposal of asbestos.
During Manufacture
Workplace Exposure—
Airborne asbestos emissions from floor tile production are of the greatest
concern as these will consist primarily of the raw asbestos fibers. Asbestos
process air emissions were estimated to be 3.6 metric tons for 1980, or 0.01
percent of all asbestos processed by the floor tile industry.16 Inasmuch as
the asbestos fibers are encapsulated once they are mixed with polymer in the
Banbury mixes, the major potential emission points for fiber release pre-
cede this mixing operation. These air emission points include fiber receiving
and storage, fiber introduction, blending and mixing. The relative severity
of emission levels in these areas, as well as in the entire production process,
is shown by a comparison of available fiber count data presented in Table 40.
TABLE 40. TIME-WEIGHTED AVERAGE FIBER COUNTS - FLOOR TILE17
Fiber count (with existing control technology)3
Process step Typical (fibers/cc) Range (fibers/cc)
Receiving and storage
1.0
<0.1 - 2.5
Fiber introduction
1.5
<0.1 - 4.3
Blending
1.75
<0.1 - 4.3
Banbury mixer
1.5
0.8 - 4.3
Milling
0.75
-
Calendering
0.75
-
Embossing
0.75
-
Cutting
0.75
-
Inspection
0.75
-
Packing
0.5
-
Scrap and rework
0.5
-
0
Optical microscope visible fibers >5 pm.
163
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The maximum permissible asbestos concentration in industry is now 2
fibers* per cubic centimeter which are greater than 5 vim in length. Workers
exposed to this concentration over a 40-hour week would inhale an estimated
2.5 billion fibers each year.18 Assuming each worker is exposed to the
average fiber count of all process steps cited in Table 40 (~1 f/cc),* then
each inhales approximately 1.25 billion fibers each year.
Emissions to Air—
Due to the limited data on atmospheric concentrations of asbestos near
manufacturing plants, an accurate assessment of nonoccupational exposure
cannot be made. However, exposure has been estimated using a binomial con-
tinuous plume dispersion model with assumed plant emissions. The affected
area is assumed to be bounded by a 5-km radius around the manufacturing
plants. The asbestos concentration within this area is estimated to be
21,000 f/m3 and the average person can be expected to inhale 115 million
fibers per year compared to 220 billion fibers for asbestos workers. As a
point of reference, the median ambient asbestos concentration for urban
areas is 5,000 f/m3.18
Receiving and storage has only an average fiber count, yet has a high
potential for ambient fiber release since there are no control devices other
than exhaust fans in this area. Asbestos is pelletized, shipped in plastic
bags and/or shrink wrapped in plastic to decrease possible emissions in this
area. In spite of these measures, the potential for accidental spills exists
and a dropped bag or pallet can result in airborne fiber release. Accidents
are most likely to occur when asbestos is being transported into and out of the
storage area. Airborne emissions in the storage area are particularly dan-
gerous since ventilation to an air pollution device is not practical. Strict
packaging requirements would serve to minimize this potential problem area.
A cyclone-type collector is used to remove pelletized asbestos from the air
stream. Worker contact using this system is significantly less than when
asbestos is transported by bag. Transport of the pellets causes some release
of fibers and is a potential source of atmospheric asbestos emissions. Ex-
haust from the conveying system is therefore filtered through a baghouse
before discharge.
Typically, plants are equipped with vacuum cleaners, respirators and
bags to aid in cleaning up spillage. Once the vacuum cleaner bags are
filled, they are labeled, securely tied and transported to a dumpster for ul-
timate disposal. Individual plant emissions from this area are impossible
to estimate as the amount of asbestos stored, the rate of accidental spillage,
the size of the storage area, and the number of air changes in this area are
all variables that change from plant to plant. Fiber counts in this area
have been found to range from 0.25 to 2.5 fibers/cc with a typical value of
1.0. By receiving asbestos in pressure-packed bags or in pelletized form on
shrink wrapped pallets, repairing damaged containers, immediately cleaning
spills and floor accumulations and vacuuming the floor at least once per
shift the fiber count can be kept at or below 0.3 f/cc.12
•k
Optical-microscope-visible fibers >5 vim.
164
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All fiber Introduction takes place beneath hooded enclosures. These
enclosures are vented to a baghouse for capture of the asbestos fibers that
are released in the batch mixing operation. The size of the enclosure and
the surface velocity maintained at the mixing face have been established to
minimize worker exposure to the asbestos fibers. The vast majority of as-
bestos released from mixing is emitted to the local mixing area which is
controlled by baghouse. Some is released directly to the atmosphere through
area rooftop ventilation ducts* however, due to the diversity of mixing rates,
mixing station configurations, and area ventilation rates, no estimates could
be made on these uncontrolled rooftop asbestos releases.
Filler, pigment, and copolymer are added to the asbestos in a blending
station. The addition of these dry ingredients increases localized dust
levels; therefore, this step also takes place under a hooded enclosure. This
enclosure is also vented to a baghouse for control of the asbestos fibers as
well as fugitive filler, polymer, etc. Analysis of the baghouse catch at one
tile manufacturing plant indicated that only 2 percent of the collected
particulate was asbestos.11* This estimate, however, is substantially lower
than other published data1 on the amount of asbestos captured in baghousea.
Therefore it should not be considered typical of industry baghouse composition.
Due to the semienclosed nature of the dry blending station, this area reported
the highest typical fiber level, as demonstrated in Table 40.
Once all ingredients have been weighed and added to the batch mixture,
the materials are transported by conveyor to a Banbury mixer where final
mixing takes place. Typically, openings are provider cn both sides of the
Banbury inlets as well as deep in the inlet throat to control emissions
generated by this mechanical transfer operation. These openings are operated
at a negative pressure and are vented to the common collection baghouses.
The asbestos is encapsulated in the plastic tile mass in the Banbury mixer,
and from here on all processes demonstrate relatively small workplace fiber
counts, and concurrent small potential atmospheric releases of asbestos
through rooftop ventilation ducts.
Release to Water—
As indicated in Figure 20, there are negligible amounts of waterborne
asbestos emissions attributable to the production of asbestos floor tile.
Water is used regularly in the manufacturing process only for cooling of the
tile after it has passed through the calenders. By this time, the asbestos
fibers have been encapsulated and will not be carried off in the waste water
stream. While the cooling water may contain dirt, oil, grease, wax, ink,
glue and other contaminants that must be treated before discharged to a
receiving water," asbestos fibers are not an environmental threat to this
waste stream. Waste water production varies for different plants from 79 to
1703 liters per 1000 pieces of tile produced.5 The lesser amounts are pro-
duced by plants using a closed system with noncontact cooling. Cooling
towers are used to dissipate heat and only periodic wasting of water is needed
to prevent scaling. When direct contact cooling is used, larger amounts of
water are needed since recycle is impossible due to a build-up of contaminants.
Water used to wash the floors of receiving and storage areas may be contaminated
by asbestos fibers. However, if these areas are thoroughly vacuumed on a
regular basis, the total quality of asbestos released to receiving waters
wiJ1 be minimal.
165
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Releabc to Lund—
In terras of absolute tonnage, solid waste containing asbestos represents
the greatest asbestos-related environmental problem, as this form of asbestos
pollution accounts for greater than 99 percent of all manufacturing-related
asbestos discharge and 99.99 percent of all end-use asbestos waste. It has
been estimated1 that 0.2 percent of production volume or approximately 72 tons
of asbestos fiber are annually collected in floor tile manufacturing baghouses.
This fiber is mixed with other tile constituents and cannot be easily ex-
tracted and recycled and is thus landfilled. Typically, baghouse waste solids
are wrapped in plastic bags or containers, labeled to alert the disposal con-
tractor of the hazardous nature of the contents, and shipped to a landfill
where they are deposited in a separate hazardous section and covered with
soil. Exposed to the mixing and transport actions of the wind, this asbestos
fiber presents a problem. Once covered with soil, however, the environmental
impact decreases substantially, as little evidence exists that the asbestos
will leach into ground waters. Asbestos fibers collected in baghouse filters
represent approximately 7.7 percent of all landfilled asbestos waste for the
entire flooring industry.
During Use
Asbestos flooring has a service life varying from 10 to 30 years, depend-
ing upon the severity of usage. Normal traffic and cleaning result in a slow
breakdown of the vinyl matrix and thus may allow a gradual release of asbestos
fiber. The major release the tile is cut to size and when old tile is removed
and disposed to landfills.1 When old asbestos flooring is removed, sanding
may be required to remove residual material. In a test simulating working
conditions during sanding, the airborne asbestos concentration was found to be
1.2 to 1.3 f/cc and the potential for greater air emissions is thought to exist
during actual working conditions.19 While atmospheric emissions from this
operation would total less than 175 ms per hour, worker exposure could exceed
OSHA regulations. A second reference has estimated the potential increase in
the average asbestos concentration in the air above an asbestos tile floor due
to use and cleaning to be from 0.008 to 0.08 fibers/cc. In order to estimate
this fiber concentration it was first assumed that each square meter of floor
tile contains 0.64 kg of asbestos, that the average service life is 20 years,
that approximately 10 percent of the flooring is worn away during the service
life by use and cleaning and that about 1 percent of the "wom-away" flooring
becomes airborne. Stated in another form, on average, 0.003 grams of asbestos
may be released to the atmosphere each year for every square foot of installed tile.
To minimize air emissions a floor can be wetted prior to sanding operations.19
Waterborne asbestos emissions from the cleaning of floor tile can be es-
timated using these same assumptions. This permits a comparison of air and
water emissions from the same activity. This calculation demonstrates that
up to 0.3 grams of asbestos are discharged to receiving waters each year for
every square foot of installed tile. This is 100 times the air emission esti-
mate and it indicates that this type of emission, while not producing high
localized emissions, may be a broad-based source of asbestos in receiving
waters and deserves follow-up investigation.
166
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During Disposal
Additional solid waste is disposed to the land in the form of manufactur-
ing waste, or used floor tile. The asbestos contained in this waste is bound
in a solid, plastic-like matrix. Unless these wastes are crushed or inciner-
ated, there should be insignificant levels of free-fiber asbestos released to
the atmosphere. Approximately 10 percent of floor tile solid waste is inciner-
ated.1 Since chrysotile asbestos (the form used in floor tile) decomposes
into a different mineral form at b80"C,1' the release of free asbestos fibers
into the atmosphere is dependent upon the temperature at which the solid waste
is incinerated. If one assumes that all incineration systems (municipal and
private) currently operating are carefully controlled to minimize particulate
emissions and that temperatures of 760° to 980°C are required for this proper
combustion, then the incineration of floor tile waste results In minimal am-
bient asbestos release. Estimated asbestos air emissions of metric tons from
tile manufacturing waste disposal as presented in Figure 20 appear to substan-
tiate these assumptions.5
CONCLUSION
According to Bureau of Mines statistics,3 the amount of asbestos used in
flooring products has decreased by approximately 48 percent from 1971 to 1980.
This decrease was considered to be a short-term phenomenon attributable to
the popularity of newer products such as carpeting, and solid vinyl flooring.
Contingency forecasts for the year 2000 made by the Bureau of Mines indicate
that the use of asbestos by the flooring industry should increase by the year
2000 to 170,000 metric tons. This forecast is based on 20-year historical
trends and assumes that the lower cost of asbestos flooring as compared to its
competitors will give it an increasingly larger share of the flooring market.
Flooring industry asbestos use is projected to increase from 25 percent of
total U.S. asbestos demand (1980) to 28 percent of asbestos consumption by the
year 2000.20 This projection assumes that manufacturers will not adjust flooring
formulas to minimize asbestos use and that asbestos flooring imports will not
displace domestic production. It further assumes that no equally low cost
substitute will be found for asbestos and that cost considerations will be the
main factor in determining the increased use of asbestos flooring. Santoweb, a
natural cellulose fiber, has been recently developed by Monsanto as a direct
replacement for asbestos in vinyl flooring. Vinyl flooring using Santoweb is
reported to have all of the desirable qualities of asbestos-vinyl at a 10 per-
cent higher cost.12 Higher cost is reported to be the main factor limiting
Santoweb use. Direct replacements for fiber-reinforced vinyl tile are also
being considered. Since replacement ol floor tile is often made for decorating
reasons and not because the tile Itself has worn out, the newer, coated types
of vinyl flooring (plastisol-coated felts) may actually garner a larger por-
tion of the flooring market in the future than has been predicted, and this
may serve to lessen the actual growth of asbestos use in the flooring industry.
The use of advanced technology in the manufacture of asbestos floor tile
would reduce the amount of asbestos released to the atmosphere by the plants due
to the increased asbestos fiber consumption predicted for the year 2000. Improved
packaging techniques, the use of pressure-packed and pelletlzed asbestos, and
167
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the use of pneumatic conveyors would not only reduce worker exposure in the
industry, but also decrease ambient emissions that result from accidental
spills, breaks, etc. These ideas are currently in use at some newer plants,
and can be expected to be installed in the new facilities that would be re-
quired to meet the increased production that is forecasted.
The flow of asbestos fibers through floor tile manufacturing facilities
is well documented. Within the plants, processes that handle raw asbestos
fiber are hooded and vented to baghouse collectors. Once the tile formula-
tions have been mixed, the asbestos fibers are encapsulated and do not present
an environmental hazard. While stricter packaging standards may be required
to minimize the effects of accidental spills, by and large, the industry is
controlling asbestos emissions reasonably well.
168
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1
2
3
4
5
6
7
8
9
10
11
12
REFERENCES
Meylan, W. M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environm;ntal Contamination:
Task III - Asbestos. EPA-560/6-78-005. August 1978.
Bikales, N. M. Executive editor. Encyclopedia of Polymer Science and
Technology, Plastics, Resins, Rubbers, Fibers. Volume 7. John Wiley
and Sons, Publishers, N.Y. 1967.
Clifton, R. A. Asbestos. 1980 Minerals yearbook. U.S. Bureau of Mines,
Washington, D.C.
Wright, M. D. , et a.l. Asbestos Dust Technological Feasibility Assessment
and Economic Impact Analysis of the Proposed Federal Occupational Standard:
Part I. U.S. Department of Labor, OSHA. September 1978. (Draft)
Sittig, M. Pollution Control in the Asbestos-Cement, Class, and Allied
Mineral Indusi ries. 1975.
Daly, A. R., et al. Technological Feasibility and Economic Impact of
OSHA Proposed Revision of the Asbestos Standard (Construction Excluded).
Asbestos Information Association/North America. March 26, 1976.
Telecon. Jooit, F. Armstrong World Industries, with Patinskas, John,
GCA. October 2, 1980.
Carton, R. J. Development Document for Effluent Limitation Guidelines
and New Sourc • Performance Standards for Building, Construction, and
Paper Segments of the Asbestos Manufacturing Point Source Category.
U.S. Environmental Protection Agency. U.S. National Technical Information
Service. PB-,'30. February 1974.
Department of Health, Education, and Welfare. Criteria of a Recommended
Standard: Occupational Exposure to Asbestos. Public Health Service.
HSM 72-10267. 1972.
Telecon. Paul Graham, Monsanto Company, St. Louis, MO, with David R.
Cogley, GCA Corporation/Technology Division. March 1980.
Telecon. Robert Luders, Sales Administration, Armstrong Cork Co., with
Ron Bell, GCA Corporation. February 28, 1980. Notebook 1, Call 18.
GAF Corporation. Document No. OTS-61005, 1980.
169
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13. U.S. Environmental Protection Agency. Control Techniques for Asbestos
Air Pollutants. February 1973.
14. Mclnnes, R. G. Trip Report on visit to Kentile Floor Company, Brooklyn,
N.Y. October 23, 1979.
15. Comments on the Advance Notice of Proposed Rulemaking on the Commercial
and Industrial Use of Asbestos Fibers. The Resilient Floor Covering
Institute. Washington, D.C. February 18, 1980.
16. Levine, R., ed. Asbestos: An Information Resource. May 1978.
17. 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.
18. Suta, B. E., and R. J. Levine. Non-Occupational Asbestos Emissions and
Exposures. Asbestos, Properties, Applications and Hazards. Volume 1.
John Wiley and Sons, New York, N.Y. 1979.
19. Murphy, R. L. et al. Floor Tile Installation as a Source of Asbestos
Exposure. American Review of Respiratory Disease, Vol. 104. 1971.
20. Clifton, R. Asbestos, A Chapter from Mineral Facts and Problems, 1980
edition. U.S. Department of the Interior. 1980.
170
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SECTION 9
GASKETS AND PACKING
INTRODUCTION
Asbestos fiber used in the production of gaskets and packing was estimated
to be 12,300 metric tons in 1980.1 This represented 3.4 percent of U.S. asbestos
consumption and ranked this category fifth in industrial asbestos use. Based
on sales data, roughly 66 percent of asbestos consumption in this category is
used for gasket production, while the remainder is used to produce packing.
Asbestos is widely used for gaskets and packing because of its resilience,
strength, chemical Inertness, and heat resistance. Asbestos gaskets and
packing have found use in both static and dynamic applications in a variety of
industrial, commercial, and residential uses as well as In motor vehicles. For
gasket manufacture, the asbestos is typically bonded under heat and pressure
with materials such as nitrile rubber or chloroprene for resistance to oil
and solvents. A wide variety of materials may be used In this compounding
process to produce a gasket with the correct temperature, pressure, and resis-
tance qualities required. Packing generally incorporates a lubricant and is
typically made by braiding asbestos yarns that are Impregnated with a grease
base lubricant. Most of the asbestos used for gaskets and packings is
chrysotlle, although a small percentage is crocldollte asbestos used in certain
high temperature applications.
The gaskets and packing industrial segment somewhat overlaps the other
asbestos categories. Gaskets may be made from compressed sheet or from
beater-add gasket paper. However, only compressed sheet manufacture will be
discussed in this section as beater-add gaskets have previously been dis-
cussed in Section 4 on asbestos paper manufacture. Similarly, packing is made
from impregnated millboard and yam, and the twisting and braiding of asbestos
fibers into yarn is also covered In the asbestos textile description in
Section 12.
PRODUCT DESCRIPTION
Composition
Specific gasket and packing ingredient formulas vary with manufacturer
and grade of product. Compressed sheet for gaskets is made from a plastic
mixture of fiber, an elastomeric binder and a solvent. The proportion of
fiber and binder in the gasket varies with the temperature at which it will
be used. Commercial grade gasket sheet contains 75 to 80 percent asbestos
and is used for temperatures of 204°C. Temperatures of 483°C or more require
gasket sheet of 99 to 100 percent asbestos. Both white (chrysotile) and blue
(crocldollte) asbestos are used up to about 483°C. Above this temperature.
171
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the chrysotile becomes unstable and use of crocidolite predominates.2 A
breakdown of asbestos consumption in gaskets and packings is shown in Table 41,
TABLE 41. ASBESTOS USED IN GASKETS AND PACKINGS1 (1980)
Asbestos type Amount (metric tons)
Chrysotile
Grade 3 800
Grade 4 2,300
Grade 5 6,200
Grade 6 100
Grade 7 2,800
Total chrysotile 12,200
Crocidolite 100
Total 12,300
——¦ ¦ ¦' —P—I—i— ¦ -
Packing is made from a dry asbestos yarn that is coated with lubricant.
Asbestos content in packing varies considerably - up to 100 percent for some
applications such as sealing furnace doors3. The impregnated yarns are
braided into continuous lengths of packing and a second impregnation may
follow. A variation of braided packing is made by extruding a mixture of
asbestos fiber, binder, and lubricants, and then braiding lubricated asbestos
yarns over the extrusion. The amount and type of lubricant and binder used
in these processes varies considerably and no "typical" formulation can be
given. Polymers used in the production of gaskets packing include phenolic
resins, furan resins, asphaltic materials, fluorocarbon polymers and rubbers.
Some typical elastomeric binders used in the packing and gasket industry
include:5'6
•
silicone based rubber
•
neoprene,
•
Buna-N rubber,
•
natural rubber,
•
nitrile rubber,
•
Teflon'*,
•
glue-glycerine,
•
styrene-butadiene,
•
nitrile Buna-N, and
•
Hypalon®.
Tables 42 and 43 list the comparative properties of some elastomers.
172
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TABI.E 42. COMPARATIVE PROPERTIES OF ELASTOMERS7
Elastomer-ASTM designation
Property
NR
SBR
CR
IIR
NBR
BR
sn.
CSM
R
Tensile strength
F
0
r,
F
C
F
p
G
—
Elongntlnn
F.
G
c.
C
F
F
—
—
—
Resilience
E
G
<:
P
F
E
G
G
—
Abrnsion resistance
G
E
c
F
C
E
P
E
G
Oil resistance
P
P
r.
P
E
P
F
F
P
Heat resistance
P
F
E
«
G
F
E
E
G
Low-tempernture
service
r.
G
F
C
P
E
E
G
G
Aging-veal liering
resistance
F
P
E
c
F
G
E
E
C
Cas impermeability
F
F
G
E
E
G
P
—
—
Flame resintance
P
P
E
P
P
—
F
G
—
Resistance to
n1coboI
G
F
F
E
E
F
—
—
—
Electrical resistivity
E
G
F
E
F
G
E
F
G
Dielectric strength
c,
F
F
E
F
—
E
—
G
Key: E - Excellent
G - Good
F - Fair
P - Poor
TABLE 43. ELASTOMER CLASSIFICATIONS7
ASTM Common ASTM Common
D-1418 Chemical name name D-1418 Chemical name name
BR
Polybutadiene
Cis-4
NBR
Acrylonitrile
CR
Chloroprene
Neoprene
butadiene
Nitrile Buena K
CSM
Chlorosul fonati'1
NR
Natural
polyethlene
Hypalon
polyisoprene
Natural rubber
TIR
Iaobutylene
SBR
Styrene-
isoprene
Butyl
butadiene
Buena S GRS
1R
Synthet it-
Synthetic
SIL
Polysiloxane
Silicone
poly I si'prene
natural
173
-------
Some of the more common lubricants used in packing manufacture are:3
•
petroleum based oils and waxes,
•
high grade animal fats and waxes
•
Teflon®,
•
mineral oil,
•
natural rubber,
•
Buna-S rubber,
•
vegetable oil,
•
glycerine, and
•
graphite.
For some applications, a lubricant may not be necessary.
Uses and Applications
Asbestos gaskets are used for static applications to obtain tight non-
leaking connections for piping and other joints, such as the covers and
openings on all types of industrial and commercial equipment. For dynamic
applications, packing is used as a form of bearing for revolving or moving
parts in stationary supporting members that also prevents leakage of the con-
tained fluid along the bearing surface. The packing, usually in the form of
rings of the material, is held by pressure against the moving part. Lubri-
cation required at the interface is provided by external or impregnated lubri-
cants. Some dry asbestos packing is used to seal furnace doors, rotary kilns
and high-temperature refractory equipment.
It has been estimated that 25 percent of gasket materials have less
than a 1-year life, 60 percent is used for maintenance and long-time
replacement and 15 percent is intended for new installations. For packing
materials, 10 percent of installed material wears immediately, and 90
percent has an annual life of 1 year or less.
Special Qualities
Asbestos has been successfully used in both gasket and packing applications
because of its unique combination of qualities. It is not only heat resistant,
resilient, and strong, but it is also relatively chemically inert which is
important for many chemical applications. Both gaskets and packings are nor-
mally composed not only of asbestos but also of some form of elastomeric
binder and, in the case of some packings, a lubricant. The asbestos imparts
strength, heat resistance, and chemical inertness to the gasket while the
binder holds the fibers together.
174
-------
Assuming the gasket is properly designed for its operating temperatures
and pressures, the service life of asbestos gaskets is influenced essentially
by two factors: (a) the reaction of the fluid being contained with the binder
and (b) scheduled and nonscheduled maintenance of the device being sealed.
Although asbestos is essentially chemically inert, the binder used with the
asbestos fibers can be affected by the fluid being contained causing the
product to fail due to binder properties rather than to the asbestos itself.
Selection of the gasket with the most inert binder for the particular appli-
cation is extremely important. Maintenance, whether scheduled or nonscheduled,
prematurely ends the service life of the gasket by requiring replacement of
the gasket, which is damaged when the seal is broken.
The service life of asbestos packings is determined primarily by wear
due to friction. Therefore, a lubricant is generally included in the binder.
In the case of pumps, the pump packing must leak to perform properly. Pump
packings serve to control leakage, not to prevent it. This slight leakage along
the shaft provides proper lubrication to the packing. Pump packings have a
lubricant which acts as a primary sealant for startup and break-in phases,
during which time the lubricant reduces friction. However, once the pump is
on line, external lubrication must be supplied to the packing to keep it
running properly and ensure the longest life possible. If not, the lubricant
in the packing will bleed out due to heat generation causing the packing to
fail.
A valve is packed differently than a pump. In contrast to a pump pack-
ing which must leak, a valve packing must not leak. Pressure and temperature
on a valve stem packing is normally much higher than on a pump packing.
To eliminate the possibility of the lubricant bleeding out of the valve
packing, a minor amount of impregnation is put into the packing. Valve stem
packings must provide a dense structure that will not permit movement of the
fluid through the body of the packing itself, thus acting more like a gasket.
SUBSTITUTES
Many different gasket and packing substitute materials are presently in
use. One manufacture* lists over 160 asbestos-free materials from which
gaskets and packings are fabricated. The particular material most suitable
for a specific application is dependent on the application.
Two types of substitute products exist for asbestos gaskets and packings:
(a) fiber-for-fiber replacements, and (b) a completely different substitute
material. The fiber-for-fiber replacements include: silica, carbon, Kevlar*,
ceramic and Teflon® fibers. Two substitute materials specifically developed
as gasket materials are Gylon® and Nu-Board.
In general, compressed asbestos sheet gasketing can be replaced with sub-
stitute materials at this time with little added expense to the customer unless
the application is over 260cC. Graphite and sheet metal gaskets can replace
asbestos over 260°C but their cost will constitute a major expenditure for
plant maintenance.
175
-------
For a fiber-for-flber replacement, the cost of packings and gaskets is
proportional to the cost of fibers as the manufacturing processes are identi-
cal. Teflon fiber is approximately 7-10 times the cost of asbestos. Graphite
(carbon) fibers cost approximately twice as much as asbestos and ceramic fiber
prices vary greatly, from approximately 9-32 times that of asbestos.9 Gylon®
ranges from 4-7 times the cost of compressed asbestos sheet, and Kevlar® 29 is
also in this range of 5.5 to 6 times the cost of asbestos.10*11 Nu-Board costs
consistently less than asbestos sheet at approximately one-half to three-quarters
that of asbestos.12
Of note here is that in many cases, the cost of the gasket or packing is
insignificant compared to the cost of its installation.13 Consequently, it is
often more cost effective to install a higher quality, higher cost material
rather than the lower cost, lower quality material. Lost production while
equipment is down due to gasket and packing replacement must also be included
in the cost of the replacement.
Specific to packings, it appears that substitute materials are both
economically and physically viable alternatives to asbestos in every appli-
cation. Since substitute materials result in less abrasion on rotating
shafts, improved heat dissipation and superior life characteristics, lower
operating and maintenance costs are experienced. As a result, the newer
synthetic packings are cost competitive with asbestos packings.
MANUFACTURING
Primary Manufacture
There are several methods of gasket production currently in use. A
typical process layout is presented schematically in Figure 21.
Raw ingredients including asbestos fiber, elastomeric binder and a sol-
vent are preweighed and added to a mixer. In some cases, the compressed raw
asbestos is dumped into a fluffer for fiber opening before the mix step. The
mixture is then blended on a batch basis until a dispersed agglomerated mass
is obtained. Mixing may be a dry or wet operation, according to the product
requirements, and multiple production lines may be employed. The mixture feeds
a sheeting machine consisting of two steel, horizontal revolving cylinders
placed at a preadjusted clearance. The smaller cylinder or roll presses the
mixture onto the larger roll, which is heated to drive off the solvent and
compact the sheet. The large roll typically is 1.02 meters in diameter by
3.3 meters in length and produces a sheet 3.05 meters square. This calendered
gasket sheet is then cut to size and packaged. This sheet may be stamped into
products on site, or as is more common, sold to secondary manufacturers for
further processing or to distributors for the maintenance market. The sec-
ondary manufacturers, such as gasket cutters, generally form gaskets from
sheets by die cutting while the maintenance user cuts the sheet manually. Im-
pregnated sheet scrap cannot be recycled and must be discarded.
Asbestos-based packing is manufactured by a variety of processes. These
are represented schematically in Figure 22. The most common process is to
impregnate dry yarn with lubricant, thereby coating the fibers. The impreg-
176
-------
SHEET FORMATION
CUTTING AND STAMPING
MIXING
FIBER INTRODUCTION
PACKAGING
Figure 21. Asbestos gasket process operations.
Source: CCA/Technology Division
177
-------
J H»KE&NA*'li
;yt*-nc
t t - *3*W1N§
'It*
•TfMODwCt rON
C*s.f WOiBi*€
03
Figure 22, Asbestos packing process flow diagram.
Source: GCA/Technology Division
-------
nated yarns are Chen braided into a continuous length of packing which is then
calendered to a specific size and cross-sectional shape. It may then be coiled,
boxed, and sold to the maintenance trade or be pressed into required shapes.
The formed product may then be coated with graphite or other materials. Fiber
or yam may also be used as reinforcement to elastomers such as rubber and
molded to desired cross-sectional shapes. A second type of packing production
involves extruding a mixture of fiber, binder, and lubricants, and then braid-
ing lubricated asbestos yarns over the extrusion. With either process, the
final step in production is packing and shipment. Prime gasket sheets and
packing are fabricated by a limited number of manufacturers. Most final cutting
and forming operations are done by a large number of secondary fabricators.
Asbestos-bearing waste is produced by both primary and secondary fabricators.
Secondary Manufacture
Although primary products such as compressed sheet and impregnated yarn
are made by the primary manufacturers, much of the material is packaged
and resold by a large number of specially companies. These secondary manu-
facturers typically rework the gasket sheets and packing yarn into desired
shapes and may sheath them in metal, plastic, or cloth or reinforce them
with wire insertions. Due to the wide variety of gasket and packing sizes,
shapes, sheathing materials and asbestos compositions available, no distinct
all inclusive product list can be made. Similarly, the number of companies
involved in secondary fabrication is impossible to estimate, although one
1975 estimate suggested that more than 200 such operations exist.*
Manufacturing Plants
Primary gasket and packing manufacturers and their plant locations are
presented in Table 44. Actual annual asbestos consumption of each plant was
unavailable. The following five manufacturers are currently marketing or
developing asbestos substitute gasket and packing products:
• Garlock Inc.27
• Greene, Tweed and Company28
• F.D. Farnham Company29
• Boise Cascade, Specialty Paperboard Division30
• Janos Industrial Insulation Corp.31
Production Volumes—
In 1980, approximately 12,300 metric tons (MT), or 13,530 short tons of
asbestos were used in thu United States to produce gaskets and packings.1
Of this amount, 12,200 metric tons was chrysotile and the remaining amount
was crocidolite.
*A listing of 200 gasketu and packing manufacturing companies may be found
in the 1980 Thomas Register.
179
-------
TABLE 44. U.S. ASBESTOS GASKET AND PACKING MANUFACTURERS2 '1,4»15 »17-26
Name3 Location
Amatex Corporation*5
Norristown, PA
Anchor Packing
Manheim, PA
Armstrong Cork Co.17
Fulton, NY
Braiding and Packing Works of America
Brooklyn, NY
A. W. Chesterton
Everett, MA
Crane Packing
Morton Grove, IL
Detroit Gasket & Mfg. Co.18
Detroit, MI
F. D. Farnum
Necedah, WI
Felt Products Mfg. Co.
Skokie, IL
Fitzgerald Gasket19
Torrington, CT
GAF20
Erie, PA
Garlock, Inc.
Charlotte, NC
Greene, Tweed and Company
North Wales, PA
Hollingsworth and Vose21
East Walpole, MA
Janak, Inc.22
Weatherford, TX
Johns Manville
Manville, NJ
Waukeegan, IL
Lamont Metal Gasket Co. Inc.23
Houston, TX
New Orleans, LA
McCord Corporation
Wyandotte, MI
Nicolet Industries
Ambler, PA
Parker Seal Gaskets21*
North Brunswick, NJ
Raybestos-Manhattan, Inc.
Stratford, CT
Richardson Corp., Hercules Division
Alden, NY
Sacomo Packing Co.
San Francisco, CA
Sacomo - Sierra25
Carson City, NV
SEPCO
Birmingham, PA
Standco Rubber Gaskets26
Houston, TX
aMost of these companies were originally noted in the references
listed, then verified by telephone contact by GCA personnel;
locations for a few were verified by the 1980 Thomas Register.
^Manufacture asbestos-containing material that eventually goes
into gaskets and packings.16
180
-------
ASBESTOS RELEASE
Input/Output
Figure 23 shows estimated process disposal and emissions for the gaskets
and packing manufacturing industry based on Levine's32 1974 estimates projected
to 1980 U.S. Bureau of Mines1 consumption figures. Of the 12,305.7 metric tons
entering the process as raw asbestos fiber, approximately 11,992 metric tons
are incorporated into the product and 307 metric tons are sent to disposal as
vacuum cleaner and baghouse dust and product scrap. An estimated 6.1 tons
escape through a control device (typically a baghouse). Levine's estimates
are based on gross assumptions with a reported uncertainty of at least an or-
der of magnitude. Meylan2 reports emissions of 1 to 3 orders of magnitude
less. Atmospheric emissions from disposal, based on GCA estimates, are shown
to be approximately 0.6 metric tons. This estimate is loosely based on Levine's92
data, and takes into account the amended asbestos NESHAPS regulations adopted
in 1975 regarding the disposal of asbestos.
During Manufacture
Workplace Exposure--
The Initial airborne emissions from the mixing process are discussed in
Emissions to Air. Once the raw asbestos fiber is mixed with binders and
solvents it is encased and presents less of an environmental problem.
The main potential fiber release areas are those that precede this mixing
operation. As with other industrial categories, raw asbestos fiber is re-
ceived at the major fabricating facilities in 23 to 45.5-kilogran bags, stacked
on pallets. The ba,;s are transported to storage areas by fork-lift truck to
await further processing. Accidental spills in this area can cause potentially
large, though intermittent, ambient fiber releases. The bags of fiber are
next transported to the fiber introduction area where the bags are opened
manually and the contents dumped into mixing tanks. These stations are hooded
and vented to baghouse collection systems to comply with OSHA worker exposure
limits. The mouth of the mixing tanks is also equipped with enclosures vented
to baghouses to prevent large workplace releases of raw asbestos fiber. Data
on emissions at different stages of the manufacturing process are presented in
Table 45.
TABLE 45. EXISTING FIBER3 COUNTS33
TWA rang*
Operation (flbers/cc)
Receiving and storage** 0.5-2.5
Fiber Introduction 0.5-2.5
Xixlng O.OU-l.O
Braiding and twisting
Sheet formation
Cutting
Packaging
*Flb«ri greater than 5 ua cnaylxed
by optical alcroacopy.
bFlbt:i count data wa* taken at
alallar operation* In other
Industrial categories.
181
-------
MANUFACTURING OPERATIONS
RAW
ASBESTOS
FlBERS
CONSUMER
VACUUMED
DUST
LEGEND
BAGHOUSE
EMISSIONS
6.1 TPY
c ^ INPUT/OUTPUT
~MANUFACTURING
PROCESSES
BAGHOUSE
CATCH
CONTROL EQUIPMENT
LANO
DISPOSAL
ULTIMATE DEPOSITION
AIR
EMISSIONS
DISPOSAL
EMISSIONS
0.6 TP*
SOLID
WATER
PACKING
RECEIVING
AND
STORAGE
MIXING
TWISTING
AMD
BRAIDING
FIBER
INTRODUCTION
307 TP* 6.7 TPY
Figure 23. Disposal and emissions of asbestos from the packing and gaskets industry
(metric tons).
-------
As the asbestos fibers are thought to be bound in the finished gasket
sheet and braided packing, only minimal fiber emissions would be expected in
secondary fabrication and product consumption, and none were reported.
There have been no actual measurements of the asbestos fiber concentra-
tion in the vncinitv of a Basket and packing mmuilacturor. HowoVcr, Suta and
Levine31* estimated concentrations uear asbestos industrial facilities using
mathematically derived dispersion curves of assumed plant emissions. In the
case of gaskets and packings, it was estimated that a population within 5 km
of a manufacturing plant would be exposed to median atmospheric asbestos
concentrations of 24.0 and 4.4 ng/m3 for urban and rural facilities respec-
tively. Comparing this data with the median U.S. atmospheric asbestos fiber
concentration (20 ng/m3), it appears that gaskets and packing facilities con-
tribute little to nonoccupational exposure. However, actual ambient moni-
toring in the vicinity of a gaskets and packing facility is necessary to con-
firm Suta and Levlne's estimates.
Emissions to Air—
There are two major sources of airborne asbestos emissions from gasket
and packing production. The first is emissions that are not captured by
process controlling baghouses. While baghouses are highly efficient collec-
tors for controlling asbestos fibers (99.99 + percent), Levine32 nonetheless
estimated emissions from these devices to be 6.1 metric tons per year.
Meylan's2 estimate is substantially lower; less than one-third of 1 ton.
This discrepancy can be attributed to differing estimates of the number of
baghouse controlled process air streams. The second source is emissions
from solvent recovery operations typically installed at each facility. These
total 0.09 to 0.18 kg/mt of finished product35 or 10 to 20 m.t. per year.
These solvent recovery emissions may be discharged to wastewater streams if
the individual facility uses a wet dust collection system. Additional,
nonpoint sources of asbestos fiber emissions include roof-top vents in the
warehouse, and fiber introduction and mixing areas of the plants.
Release to Water
Water Is not used in the direct manufacture of gaskets and packing.
Sheet gasket production may involve cooling and solvent recovery operations
that generate wastewater streams; however, such plants are not common.
Asbestos fiber release to receiving waters is therefore negligible. The in-
frequent washing of warehouse floors containing residual asbestos from acci-
dental spills is a potential source of waterborne asbestos although the annual
amount of fiber released would be minimal.
Release to Land
As with the other industrial categories, the vast majority of asbestos
discharged to the environment from the production and consumption of gaskets
and packing is in the form of solid waste. As indicated in Figure 23, 98.0
percent of all asbestos disposed or emitted from this product group is solid
183
-------
waste. This waste Is in the form of asbestos fibers collected in baghouse
control devices and scrap from production and consumption in which the as-
bestos is contained in a binder matrix. Meylan2 has estimated the amount
of asbestos fiber annually collected in gasket and packing plant baghouses
to be 35 tons. Based on 1980 consumption data, an estimated 13.8 tons of
baghouse waste was generated. This material represents 4.5 percent of all
solid waste generated by the production of gaskets and packings. Waste
collected by the baghouses presents the greatest environmental hazard as it is
in fiber form, and could be discharged to the atmosphere if not properly
handled and landfilled.
The remainder of the manufacturing solid waste is scrap generated from
stamping of individual gasket and packing pieces. Since the scrap cannot be
reused or recycled once plastic binder has been added to the asbestos, primary
and more often secondary manufacturers dispose of it to landfills, incinerators,
etc. Similar bound asbestos is disposed of by product users. Various sources
estimate that between 63 and 80 percent of all asbestos gaskets and packing
produced in a given year are released to the environment In the form of used
product waste by gasket and packing consumers.2 *32 While the asbestos contained
in this waste is generally encased, its ultimate disposal has not been fully
documented, as there are thousands of users of these products.
During Use
The consumer use of gasket and packing material will generate water-
borne asbestos. This asbestos is primarily released when packing material
wears and enters process water systems. The specific release points have not
been widely investigated and the 25-ton emission estimate by Levine32 is an
order of magnitude estimate. As gasket material, asbestos is fully bound in
a binder matrix, no water discharge is expected from the consumption and final
disposal of this product.
During Disposal
The Release to Land section above has already discussed most of the
potential environmental concerns associated with the disposal of asbestos-
containing gasket and packing waste. Meylan2 estimated that between 0.5
to 1.0 percent of gasket and packing production is discarded as waste material.
This material, excluding control device waste, would primarily consist of
trimmings and cutting. Because most of the gaskets and packing material is
Impregnated with some organic binder, this material cannot be recycled. This
condition is actually beneficial with respect to disposal because the asbestos
fibers are bound within the product matrix and are not likely to be released
to the environment during disposal. As indicated previously, 25 percent of
gaskets and 90 percent of packing material do not have a useful life span
beyond one year.
184
-------
CONCLUSION
Fiber release from asbestos gasket and packing manufacturing facilities
results from emissions that are not captured by process controlling baghouses
and from solvent recovery operations. It has been estimated that baghouse
emissions to the atmosphere amount to only 0.005 percent of all asbestos used
by the industry,2 while emissions from solvent recovery operations amount to
10 to 20 m.t. per year or 0.03 to 0.06 percent of Industry asbestos consump-
tion. Emissions from solvent recovery may be discharged to wastewater
streams if companies utilize wet dust control systems.
One of the greatest environmental hazards associated with the gasket and
packing industry is the potential for asbestos fiber collected in baghouses
to be discharged to the atmosphere if not properly handled and landfilled.
Wetting methods and bagging procedures by designated personnel using good work
practices are essential in eliminating dust emissions resulting from waste
handling. Fiber releases from scrap waste is thought to be insignificant
since the asbestos is bound in a binder.
Based on the Bureau of Mines statistics; which are approximations, the
amount of asbestos consumed by the gaskets and packings industry has declined
60 percent between 1978 and 1980. This decline may be attributed to a turn-
down in the economy and an increase in the availability and use of asbestos
substitutes. Currently, in packing materials, synthetic fibers are the
preferred choice over asbestos in almost every application. Likewise, in
gasket applications under 260°C, there are a variety of substitutes which can
replace asbestos with little added expense to the user. However, in gasket
applications over 260°C, asbestos appears to have advantages (principally
lower costs) over substitute materials. Graphite and metal gaskets can
replace asbestos over 260°C but their costs are somewhat prohibitive. There
may be many substitute fibers available that have yet to be tried because of
the historically low cost and availability of asbestos.
185
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REFERENCES
1. Clifton, R. A. Asbestos. 1980 Minerals Yearbook, U.S. Bureau of Mines.
Washington, D.C.
2. Meylan, W. M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination:
Task III - Asbestos. EPA-560/6-78-005. August 1978.
3. Johns-Manville Corporation. Sealing Components, Comprehensive Guide
to Mechanical Packings, Ropes & Tapes. PK-401. Ken-Caryl Ranch,
Denver, Colorado. April 1978. 65 pages.
4. Bikales, N. M. Executive editor. Encyclopedia of Polymer Science and
Technology, Plastics, Resins, Rubbers, Fibers. Volume 7. John Wiley
and Sons, N.Y. 1967.
5. Johns-Manville Corporation. Sealing Components, All You Need To Know
About Gasket Materials. PK-132. Ken-Caryl Ranch, Denver, Colorado.
November 1979. 17 pages.
6. Armstrong, Industry Products Division Accobest®, Accopac®, Armstrong
Gasket Material Specifications. IP-926-175x. Lancaster, Pennsylvania,
5 pages.
7. The Chemical Rubber Co., Handbook of Tables for Applied Engineering
Science. Cleveland, Ohio. March 1970. Page 122.
8. Excelsior, Inc., Advertising List of Raw Materials Publication Number
49758. p.l. Rockford, Illinois.
9. Armco. Hitco Materials Division. Hitco Aerospace Materials. LHT-MD-3278
3M TC 9-78. Gardena, California. September 1978. 5 pages.
10. Colt Industries, Garlock Inc. Mechanical Packing Division, Industrial
Packing. Gylon. GSK-292. Palmyra, New York. January 1980.
11. Chiostergi, R., Marketing Manaber, E. E. DuPont de Nemours & Co. Inc.,
Wilmington, Delaware, (302) 999-3951, Personal Communication with
Mr. Henderson, GCA/Technology Division, February 1, 1980. Notebook
No. 07, Phone call No. 20.
12. Telecon. Connolly, T. Janos Industrial Insulation Corp., Moonachie,
N.J. with T. Curtin, GCA/Technology Division. February 27, 19o0.
Notebook No. 6, Phone call No. 42.
186
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13
14
15
16
17
18
19
20
21
22
23
24
25
Swanson, R. C., Sales Representative, Colt Industries. Garlock Inc.
Mechanical Packing Division, Charlotte, N.C. Meeting with Mr. T. Curtin,
GCA Corporation, February 21, 1980.
Wright, M. D., et al. Asbestos Dust Technological Feasibility Assessment
and Economic Analysis of the Proposed Federal Occupational Standard:
Part I. U.S. Department of Labor, OSHA. September 1978 (Draft).
Arthur D. Little of Canada and Sores, Inc. Characterization of the
U.S. Asbestos Paper Markets. Report to the Government Du Quebec,
Minstere De L1Industrie Et Du Commerce. May 1976.
Telecon. Tony Rokos, Amatex, with Anne Duffy, GCA Corporation, GCA/
Technology Division, May 4, 1981, Call No. 36.
Telecon. Mr. Ambursal, Armstrong Cork Co., Lancaster, PA, (717) 397-0611,
with Anne Duffy, GCA Corporation, GCA/Technology Division, April 16, 1981,
Call No. 20.
Telecon. Sales Representative, Detroit Gasket and Mfg. Co., Detroit, MI,
(313) 968-1200, with Anne Duffy, GCA Corporation, GCA/Technology Division,
April 16, 981, Call No. 21.
Telecon. Company Representative. Fitzgerald Gasket, Torrington, CT,
(203) 482-9366, with Anne Duffy, GCA Corporation, GCA/Technology Division,
May 4, 1981, Call No. 37.
Telecon. Harvey Loud's Office, GAF Corp., New York, NY, (212) 621-5000,
with Anne Duffy, GCA Corporation, GCA/Technology Division, April 13, 1981,
Call No. 1.
Telecon. Mr. McDoughall, Hollingsworth and Vose, East Walpole, MA,
(617) 668-0295, with Anne Duffy, GCA Corporation, GCA/Technology Division,
April 16, 1981, Call No. 22.
Telecon. Company Representative. Janak Inc., Weatherford, TX
(817) 549-8771, with Anne Duffy, GCA Corporation, GCA/Technology Division,
May, 4, 1981, Call No. 38.
Telecon. Raymond Croucheck, Lamont Metal Gasket Co. Inc., Houston, TX,
(713) 222-0287, wtih Anne Duffy, GCA Corporation, GCA/Technology Division,
May 4, 1981, Call No. 39.
Telecon. Company Representative. Parker Seal Gaskets, North Brunswick, NJ,
(201) 247-6800, with Anne Duffy, GCA Corporation, GCA/Technology Division,
May 4, 1981, Call No. 40.
Telecon. Company Representative, Sacomo-Sierra, Carson City, NV,
(702) 882-7560, with Anne Duffy, GCA Corporation, GCA/Technology Division,
April 17, 1981, Call No. 23.
187
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26. Telecom Company Representative. Standco Rubber Gaskets, Houston, TX,
(713) 944-3160, with Anne Duffy, GCA Corporation, GCA/Technology Division,
May 4, 1981, Call No. 42.
27. Swanson, R. C», Sales Representative, Colt Industries, Garlock Inc.
Mechanical Packing Division, Charlotte, N.C. Meeting with T. Curtin,
GCA Corporation, February 21, 1980.
28. Koehler, S., Product Manager, Greene, Tweed & Co., North Wales
Pennsylvania, (215) 256-9521, Personal Communication with T. Curtin,
GCA/Technology Division, February 22, 1980. Notebook No. 06, Phone call
No. 40.
29. Pafsarella, M., Laboratory Director, F. D. Farnham Co., Necadah, Wisconsin,
(608) 565-2241. Personal Communication with Mr. Curtin, GCA/Technology
Division, February 11, 1980, Notebook No. 06, Phone call No. 022.
30. Call, M. Product Development Manager, Boise Cascade Specialty Paperboard
Division, Beaver Falls, New York, (315) 346-6111. Personal Communication
with Mr. Curtin, GCA/Technology Division.
31. Letter and attachments from Connolly, T. J., Janos Industrial Insulation
Corp., to T. Curtin, GCA/Technolgoy Division, February 21, 1980,
information on asbestos substitutes.
32. Levine, R., ed. Asbestos: An Information Resource. May 1978.
33. 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.
34. Suta, B. E., Levine, R. J. Non-Occupational Asbestos Emissions and
Exposures. Asbestos, Properties, Applications and Hazards. Volume 1.
John Wiley and Sons, New York, N.Y. 1979.
35. Gregg, R. T. Development Document of the Effluent Limitations Guidelines
and New Source Performance Standards for the Textile, Friction Materials
and Sealing Devices Segment of the Asbestos Manufacturing Point Source
Category. U.S. National Technical Information Service. PB-240-860.
December 1974.
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SECTION 10
SEALANTS
INTRODUCTION
Various types of paints and protective coatings containing asbestos fibers
are considered under the category "sealants." Asbestos is used as a filler
and reinforcement agent for asphalt and tar bases to improve strength and cor-
rosion resistance as well as serving to add other important qualities to the
products, such as fire resistance or sound deadening attributes. Products
considered in this category are many and varied, ranging from sealants used in
waterproofing concrete foundations and various other structures such as mobile
homes, to chimney stack paints. Many different products are or have been pro-
duced including automobile undercoatings, wood block and concrete floor mas-
tics, tennis court coverings, spackling and drywall joint compounds, texture
paints, and protective coatings for underground pipelines. The basic batch or
semicontinuous process used in manufacturing is shared across the board for
these products, with raw material input being the variable in determining the
end product desired.
Information gathered for this report was derived from a combination of
efforts, including an extensive literature search, on-site plant visits, and
telephone contact, both with industry and other representatives.
PRODUCT DESCRIPTION
Composition
Asbestos roofing products use finest grade 7 chrysotile asbestos 99 per-
cent of the time. Coatings and paints also use chrysotile asbestos, with over
95 percent consisting of grade 7. Table 46 shows the distribution of asbestos
by type and grade. About 90 percent of the milled asbestos is imported from
Queb ec.2
Bituminous coatings considered here contain 10 to 12 percent asbestos,
with 50 percent of their composition being volatile petroleum solvents.2 The
remainder consists of other ingredients, such as rust proofing chemicals, pig-
ments, heat reflecting metallic paints, and miscellaneous fillers. Additional
insulation materials, such as cork, emulsifiers, and resins may also be used.
These solvents are added to reduce viscosity, especially in spray applications
and emulsions. The asbestos fibers are thought to be completely bound by all
of these additives in the final product.
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TABLE 46. DISTRIBUTION OF ASBESTOS MINERALS USED FOR
COATINGS, PAINTS, AND SEALANTS (1980)1
Asbestos type
and grade
Quantity
(metric tons)
Chrysotile
Grade 4
100
Grade 6
100
Grade 7
10,700
Total Asbestos metric tons/yr
10,900
Uses and Applications
Asbestos-containing sealants are used in a wide variety of applications
by everyone from homeowners to private roofers to large construction companies.
Roofing applications represent the largest use. Otherwise, coatings may be
applied both as light sealants or as heavier coatings, depending upon asbestos
content and the number of coats applied. Mixes are applied to surfaces by
brush, spray gun, roller, or trowel. Product uses are many and varied.
Patching compounds represent the roofing applications, while sealants can
also be used as protective coatings for underground pipelines. Concrete
foundations, side walls, tanks, and structures such as cooling towers in
nuclear power plants and mobile homes may all use asbestos-containing seal-
ants for their moisture/waterproofing attributes.. Anticondensation asbestos
coatings are made for low temperature refrigeration service. Products ex-
posed to seawater spray, salt solutions, organic acids, mineral acids, or
petroleum products may use asbestos coatings for resistance to corrosion.
Asbestos is also used in the automotive market for automobile undercoatings
because it acts as a sound deadener in addition to its other properties.
Wood block and concrete floor mastics may contain asbestos, as well as flashing
and tile cements used in construction. In addition, many other building con-
struction needs such as spackling (for patching and repairing plastered walls)
and drywall joint compounds (used for finishing gypsum wallboard walls) have
also been met with asbestos-containing mixtures. In 1977, regulations were
drawn up to prohibit asbestos use in the manufacture of these products.
However, asbestos is still present in many buildings where these materials were
used in the past.
Special Qualities
Asbestos fibers are present in many of the products mentioned due to
inherent properties that, at present, asbestos alone exhibits. Asbestos
fibers improve and stabilize the strength of the product, increase the
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products' resistance to corrosion and rot and gives insulation and fire resis-
tance. In addition, asbestos has the high tensile strength necessary for
reinforcing asphalt and cement matrices, it maintains the dimension of the
product, and it avoids the disintegration that may occur with the use of
alternative organic reinforcement materials. The effects of temperature
changes on sealants may be controlled with asbestos, and the tendency of the
binder to flow or crack with changes in temperature is reduced. Asbestos
provides increased resistance to weathering, oxidation, and other wear factors,
as well as enhancing thixotropic characteristics, and assists in the deadening
of sound. Although other materials exist that may possess one or more of these
qualities, none has been found that suitably combines all of the essential
properties that asbestos fulfills.
Roofing Sealants—
Asbestos as an ingredient in roofing sealants is unique because of its
affinity for asphalt, fiber fineness, and its strength. Asbestos controls the
viscosity of the coatings allowing them to be applied on nonhorizontal surfaces
without the flow of asphalt which would result in the loss of waterproofing
abilities. The tensile strength of asbestos is higher than that of other fibers
resulting in a stable product which resists weathering and adheres well to
protected surfaces.
Automobile and Truck Undercoating—
The properties of asbestos that are important for automobile and truck
undercoating products are high thermal resistance, affinity for asphalt to
control viscosity, high fiber density, strength, and durability. The affinity
for asphalt is required to ensure complete encapsulation of fibers. Small
fiber dimensions result in a high density product with soundproofing abilities.
High tensile strength is needed to hold the product together and thermal resis-
tance is required to retain this strength at the elevated temperatures experi-
enced. Control of viscosity is required to retain this strength at the elevated
temperatures and prevent unwanted flow of the product resulting in loss of
waterproofing abilities.
SUBSTITUTES
The general consensus of the asbestos industry is that, for most sealant
products, no viable substitutes for asbestos exist at this time. An accept-
able substitute must be:
• Noncombustible
• Resistant to decay, many acids, and vermin
• Made up of long, flexible fibers
• Strong enough to reinforce other binders
• Unaffected by temperatures up to 500°C (930°F)
• Economic
There are no substitutes available which possess all of the above, but for
applications where only several of the characteristics are necessary, a
substitute may be available.
191
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Several companies have investigated the use of alternative fibers such as
fiberglass, polyethylene, polypropylene, polyesters, acrylics, cotton, and
other threads and fibers for use in roofing coatings and cement, but none
has proven to be an acceptable substitute for asbestos.3-6 A major problem
in LhaL none of the above become wetted by the asphalt. They "ball-up" when
applied with a trowel.3 Fiberglass provides adequate reinforcement but does
not contribute to the viscosity of the product and lacks chemical affinity
for asphalt. A number of proprietary materials are presently being investi-
gated but more specific information is not available in most cases. All
commercially available fibers are more expensive than asbestos. Grade 7
chrysotile asbestos costs between 0.13 and 0.26 $/kg whereas fiberglass,
polypropylene, cellulose, cotton and a proprietary fiber used by Tremco Inc.
range from 0.44 to 2.97 $/kg.1'5 The substitution of an alternative fiber
for asbestos may require a manufacturing process change which would involve
additional cost.
No suitable substitute is being manufactured to replace asbestos in auto-
mobile and truck undercoating uses. Zinc coating can be used to provide resis-
tance to rusting but, by itself, is not sound deadening.3 Zinc coating is
often used in combination with asphalt/asbestos undercoating. A representative
of Chrysler Corporation suggests that fiberglass, fibrous alumina and magnesium
silicate fiber might be used as substitutes although they cost 4 to 30 times
as much as Grade 7 chrysotile. These materials do not possess affinity for
asphalt or the ability to control viscosity which make asbestos unmatched for
use in undercoating products.7
Asbestos is used in nonasphalt-based coatings to provide resistance from
alkali, acids, water, and weather. Table 47 lists substitutes for these
applications.
A representative of Dudick Corrosion-Proof Manufacturing, Inc., states that
they have a new proprietary formula for acid and alkali resistant tank
linings.9 However, at this time, no specific information on this product has
been made available. Electro Chemical Engineering and Manufacturing Company
has tried high temperature glass as a substitute for asbestos in asphalt mas-
tics. It did not prove to have the necessary affinity for asphalt and there-
fore could not be sprayed to produce a desirable pattern.10
Major texture paints manufacturers (Bondex International and The Synkoloid
Company) indicate that asbestos is no longer used in texture paints.11'12
This has been confirmed by several minor manufacturers and distributors. The
elimination of asbestos from texture paints followed the ban issued by the
Consumer Product Safety Commission on the use of asbestos in the manufacture of
consumer patching compounds. Several companies which manufacture the patching
compounds also produce texture paints.
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TABLE 47. PHYSICAL AND RESISTANT CHARACTERISTICS OF COATING
AND SEALANT MATERIALS.8
Resistant characteristics
Name
Alkali
Acid
Water
Weather
Physical characteristics
Talc
F
G
E
E
Fibrous-platelike
Asbestos
F
G
E
E
Fibrous
Barite
G
G
G
G
Cubical, heavy
Diatomite
P
E
E
E
Porous
Silica
P
E
E
E
Hard, sharp crystals
Clay
F
G
F
G
Platelike
Mica
G
G
G
G
Platelike, used to reduce
moisture vapor transfer
Key: P = Poor G = Good
F = Fair E = Excellent
Properties that are required for an asbestos substitute are resistance to
vermin, heat, ozone, and ultraviolet and infrared radiation.13 The substitute
must also be available in various fiber dimensions to produce differing textures.
Possible substitutes include fiberglass, rayon, nylon, polypropylene, polyester,
and hemp fiber. Other fillers which can be used are clays, diatomite, talc,
perlite, silica, mica, barite, calcium carbonate, bentonite and others. None
possess the combination of properties attributable to asbestos. The organics
react with infrared, ultraviolet and heat radiation and ozone; hemp is often
attacked by vermin, and the inorganics do not possess the fibrous structure
necessary to bridge cracks. Texture is now often produced by worker's tools.llf
Some nonasbestos products cost no more than asbestos products with prices of
substitute fibers ranging from 0.11 $/kg (versus 0.13 to 0.26 $/kg for asbestos)
up to nylon at 1.32 $/kg.
MANUFACTURING
Small manufacturing plants usually have one production line for all seal-
ants produced, whereas larger plants have a wide product mix with several
production lines oriented to a specific product. Production facilities for
coating, painting, and sealant products are the same as for roofing coatings
except that they are usually designed for a significantly lower market require-
ment. Consequently, coating operations will usually operate on a part-time
basis, producing roofing coating products as well as other coatings containing
no asbestos. For instance, one major manufacturer of roof coating emulsions
and joint insulation compounds indicates that asbestos emulsions for roof
193
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coatings are made 5 days per week in a one- or two-shift operation.15 Other
facilities are used less frequently to manufacture joint insulation. Because
of seasonal fluctuations in demand, the plant generally operates one shift
from November through March and two shifts otherwise.1
Primary Manufacture
Sealants are produced by batch processes with a simple, general produc-
tion cycle. Basically, the fiber is introduced, fluffed, put in a batch
mixing tank, mixed with asphalt or tar and solvents or other additives as
required for an even dispersion, pumped to packaging (containerizing) opera-
tions, and finally shipped out to market. Figure 24 is a simple process flow
diagram for sealant manufacture. A more detailed description follows.
First, pallets of bagged asbestos are moved from a shipping or storage
area to a staging area where they are weighed according to specific amounts
needed for each product. The bags may be manually slit or a machine may be
utilized to help minimize worker exposure. The asbestos is then dumped
either directly into a hopper or into a fluffing machine while the shipping
bags, which contain some residual asbestos fiber, are sealed in clean plastic
or paper containers for ultimate disposal at a landfill. This machine is used
to break down the compressed fibers, causing them to become open and free,
enabling dispersion and more complete encapsulation during asphalt mixing.
Typically, fluffed asbestos fiber is transferred to hoppers or directly to a
batch mixing tank.17 Fiber transfer at this stage may be pneumatic, mechanical
(conveyors), or manual. Pneumatic transfer systems are enclosed, with bag
filters being used for the exhaust air. Generally, conveyor systems are also
enclosed. Manual transfer may be used in small operations or for specialized,
low-volume requirements.
The next step is to mix the fluffed fiber and other dry ingredients with
the asphalt (and solvents as required) in a batch tank. Mixing takes place
until the material is evenly dispersed. Shortly after mixing, the asbestos
fiber is bound by the asphalt and upon completion of the mixing, the asbestos
is considered completely bound in the asphalt with little chance of
fiber dust exposure.17 As a batch is finished, the material is pumped to the
packaging (containerizing) operation and placed in containers whose size
varies with the product. The predominant packaging for coatings is 5-gallon
metal pails with sealed lids. Special orders may use drum containers. Bulk
shipments in tank cars may take place, but are infrequent.
The batch sizes produced may vary from several hundred gallons for small
manufacturers with one production line to several thousand gallons for larger
manufacturers who are able to have a wide product mix and several production
lines in different locations (partitioned work areas or separate buildings)
oriented to a specific product.17 The batch sizes vary with size of company,
type of product, method of containerization, type of existing equipment, and
size of order. Sealant products are shipped out ready for distribution and
use; therefore, there are no secondary producers considered here.
194
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RAW ASBESTOS FIBER
\
/
FIBER RECEIVING
AND STORAGE
\
f
FIBER INTRODUCTION
(H)
t
MIXING/COMPOUNDING
\
t
PACKAGING
\
t
CONSUMER
(H) - Indicates hooded operations
Figure 24. Process flow diagram for the manufacture
of paints, coating, and sealants.16
195
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Manufacturing Plants
There are six major manufacturers of asbestos sealant products in the
U.S with many different plant locations, as shown in Table 48. Most of the
production involves roofing products. In addition, 27 major companies sell
asbestos paint products, and there are about 100 more suppliers of asphalt
paint, which may add asbestos to their products without being classified as
asbestos paint vendors.19 Many suppliers may only mix the paints, while others
pack and resell the mixed products. There are also numerous small suppliers
who mix smaller quantities of asbestos coatings for limited local markets.
Roofing compound figures are difficult to assess as they are often buried
within other roofing product totals. It is estimated that roof coatings are
produced at a maximum figure of 3 million gallons per year.2
TABLE 48. NATIONAL MANUFACTURERS OF ASBESTOS
SEALANT PRODUCTS
2,18
Manufacturer
Plant location
Product
Celotex Corporation Lockland, OH
(A Division of Jim Houston, TX
Walters Corporation) Memphis, TN
Roofing products
Roofing products
Roofing products
GAF Corporation
Gibson Homans Co,
Johns-Manville
Koppers
Monsey Products Co.*
Millis, MA
S. Bound Brook, NJ
Cleveland, OH^
Waukegan, IL
Manville, NJ
Savannah, GA
Marrero, LA
Los Angeles, CA
Fort Worth, TX
Pittsburg, PA
Youngstown, OH
Wickliffe, OH
East Rutherford, NJ
Garland, TX
Kimberton, PA
Rock Hill, SC
Troy, NY
Roofing products
Roofing products
Roofing products
Roofing
Roofing
Roofing
Roofing
Roofing
Roofing
Roofing
products
products
products
products
products
products
products
Roofing products
Roofing products
Roofing
Roofing
Roofing
Roofing
Roofing
products
products
products
products
products
*Telecon with manufacturer.
'Corporate headquarters; other branches throughout the U.S.
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Production Volumes
Sealant manufacturing consumed approximately 10,900 metric tons of asbestos
or 3.0 percent of all asbestos used in the United States in 1980, according to
the Bureau of Mines.1 No census information regarding the value of products
is available. The value of asbestos consumed in 1980, calculated from Bureau
of Mines consumption data and current asbestos prices, is $2.13 million. An
expenditure of $2.13 million represents 1.1 percent of total annual sales for
sealants which amount to approximately $200 million.
ASBESTOS RELEASE
Input/Output
Figure 25 shows estimated process and disposal emissions for the asbestos
sealants manufacturing industry based on Levine's20 1974 estimates projected
to 1980 U.S. Bureau of Mines1 consumption figures. Of the 10,900 metric tons
entering the process as raw asbestos fiber, approximately 10,790 m.t. are
incorporated into the product and 109 metric tons are disposed as vacuum
cleaner and baghouse dust. An estimated 0.6 metric tons escape through a
control device (typically a baghouse). Levine's atmospheric emissions esti-
mates are based on gross assumptions with a reported uncertainty of at least
an order of magnitude. Atmospheric emissions from disposal, based on GCA
estimates are shown to be 0.5 metric tons. This estimate is loosely based on
Levine's20 1974 data, and takes into account the amended asbestos NESHAPs
regulations adopted in 1975 regarding the disposal of asbestos.
During Manufacture
In the fiber receiving and storage area asbestos is received by truck or
railroad car in 23, 32, and 45 kilogram polyethylene bags. Accidental Spillage
is the greatest potential cause of fiber release in this area. Spills generally
occur when asbestos is being transported into and out of storage. In an effort
to minimize emissions, bags of asbestos are often received on shrink-wrapped
pallets. It is also a standard practice to tape ripped or torn bags and
immediately vacuum any spilled fiber. Respirators are worn by workers wherever
loose asbestos fiber is handled. Aside from receiving and storage, release
of asbestos to the environment during the manufacture of sealant products
normally consists solely of fiber released from initial bag opening and dumping
operations. In most of the newer plants these operations are hooded and vented
to baghouse filters. Pollution control equipment is lacking in some of the
older and smaller plants and dust capture hoods are exhausted to the atmosphere.
One plant, visited by GCA personnel, was equipped with no pollution control
equipment other than an automatic bag opener. The bag opening and mixing pro-
cesses were hooded, but were vented directly to the atmosphere. Baghouses,
cyclones, and wet scrubbers were all absent from the plant operations.15 After
fiber introduction it is believed that no control equipment is either installed
or, perhaps, required from the mixing area right through to the end of the
manufacturing process.17
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MANUFACTURING OPERATIONS
RECEIVING
AND
STORAGE
RAW
ASBESTOS
FIBERS
MIXING
AND
COMPOUNDING
FIBER
INTRODUCTION
PACKAGING
CONSUMER
10,790 TPY
10 , 900 TPY
BAGHOUSE
VACUUMED
DUST
LEGEND
INPUT/OUTPUT
| 1 MANUFACTURING
I J PROCESSES
BAGHOUSE
EMISSIONS
0.6 TPY
CONTROL EQUIPMENT
ULTIMATE DEPOSITION
SOLID
AIR
EMISSIONS
LAND
SPOSAL
WATER
DISPOSAL
EMISSIONS
0.5 TPY
109 TPY i
1
Figure 25. Input/output estimates for the asbestos sealants industry (metric tons).
-------
Emissions To Air
Assuming that baghouses with particulate removal efficiencies of 99.99
percent21 are used to control asbestos release during fiber introduction and
that 10,900 metric tons of asbestos were consumed in 1980, annual fiber
release would amount to 1.1 tons. This estimate concurs with that made by
Meylan.2 Following Levine's20 methodology, however, only 0.3 tons would be
emitted. The range of 0.3 to 1.1 tons reflects differences in calculating
assumptions. This range allows for differences between manufacturing methods
and the amount of particulate control. The dust from bag filters and
uncontrolled vents is the only release in which fibers are in free-fiber
form, as the other effluents produced during manufacture such as washing,
floor spills, and wastage of the bitumastic product, contain asbestos fibers
which have been bound in the binder.
Fiber concentration data collected in 1976 for 12 processing steps
indicate that only four of the locations would meet the 2.0 fiber/cc TWA
standard, with one exceeding 5 fiber/cc.*17 Table 49 presents the results
of the study which revealed typical exposure levels of 2.5 fibers/cc in the
fiber introduction step, where the highest readings occurred. None of the
reporting manufacturers met the 0.5 fiber/cc 8-hour TWA proposed standard.
Sealants display low levels of asbestos fibers in the primary production stages,
also no machining or cutting processes are needed in sealant production.
Release To Water
No significant asbestos-laden water effluents are generated during the
manufacture of sealants.2 Water is not used directly in the product manu-
facturing process. The infrequent washing of warehouse and production area
floors containing residual asbestos from accidental spills is a potential
source of waterborne asbestos although the annual amount of fiber release
would be minimal.
Release To Land
Asbestos-containing solid wastes generated during the manufacture of
sealants include control device and housekeeping wastes, empty asbestos
wrappers, and scrap product. Control device and housekeeping wastes, esti-
mated to be 109 metric tons based on 1980 consumption figures, are commonly
sealed in disposable containers and hauled to a landfill. Empty asbestos
wrappers are disposed of in a similar manner. It has been estimated that
several thousand emptied asbestos bags are disposed of by a single coating
manufacturer annually.17
*More recent data, showing that fiber levels at all stations are at or
below the 8-hour TWA asbestos standard, are generally not publicly
available.
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TABLE 49. TIME-WEIGHED AVERAGE FIBER COUNTSa-PAINTS,
COATINGS, AND SEALANTS1?b
Process
Fiber count with existing
control technology
Fiber count with
best available
technology0
step
Typical Range
Fibers/cc Fibers/cc
Fibers/cc
1
Receiving &
storage
1.0 0.25 to 2.5
0.5 to 1.0
2
Fiber intro-
duction
2.5 1.5 to 8.0
1.5
3
Mixing, com-
pounding
-
-
4
Packaging
-
-
^IOSH Method, counting fibers 5 Mm or longer by optical
microscopy.
Data Base: Data collected from plants consuming 30 percent
of the asbestos used in the manufacture of Paints, Coatings,
and Sealants.
c
Projected fiber counts are estimates of average exposure
after implementing BAT. Variations of these values are
expected depending upon individual installation.
Sealant manufacturers do not generate significant amounts of scrap.
Given the high costs of raw materials and the relative ease with which
off-specification products can be reworked for sale, these types of operations
do not produce much in the way of manufacturing wastes. Scrap that must be
disposed of would pose minimal environmental concern because the asbestos
fibers are bound within the product matrix.
During Use
Release of asbestos fibers during use of the sealant products will occur
from the following sources:
1. Wastes during application
2. Losses from in service weathering, wear, corrosion, etc.
3. Scrap from maintenance, replacement, and final demolition of
the structure or equipment.
200
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In nearly all of these losses, the asbestos fibers should be completely en-
cased in the bituminous binder. Consequently, only small quantities of
free fiber as airborne material are likely to be released.
The removal of texture paints containing asbestos from the substance to
which they were applied is one area of concern in regard to release of free
fibers. Inhalable asbestos fibers may be released during paint removal by
sanding or some other similar activity.2 Textured paints are likely to
present the greatest potential problem here as they are probably the only
application where sanding is used for removal. However, no monitoring data
is available that could more accurately quantify free-fiber releases from
coatings or paints.
Likewise, there is also a lack of monitoring data available to indicate
the amount of asbestos released from roofing materials during use. For in-
stalled products, this release would come essentially from scrapping worn out
material to which roofing compounds had been applied. The eventual fate of
such material is in landfills or trash dumps. The potential fiber release for
this use requires more study before an accurate accounting can be reached.
The amount of fiber release from weathering processes acting on roofing
materials would, again, require monitoring, for perhaps extended duration.
Waste released as spillage, wastings, and scraps during application of
coating and paint compounds accounts for an average of 1 percent of their
annual consumption.17 Scraps left in their container pails as well as a portion
of spillage is disposed of in landfills, while other spillage and washings
may instead be diverted to municipal or plant sewer systems. Asbestos fibers
contained in this waste would eventually settle as deposits in the disposal
system used.2 About 200 m.t. of asbestos are thought to be deposited annually
in this manner.
During Disposal
Usual maintenance and replacement rates for industrial equipment account
for a loss of asbestos representing about 2,500 metric tons or 25 percent of
the annual consumption.2 Loss of asbestos fibers also occurs when the bitumi-
nous binder in coating and paint compounds becomes oxidized, cracked, or actually
peels off the substance it was originally applied to. Rain, spray, corrosion,
wear, or water condensation may flush off large pieces of such material,
delivering them to floors, the ground surface, or other surrounding areas. The
particles may in time show up in the ground water supply, or be routed to pro-
cess or municipal sewers or drainage systems, where again, they end up as de-
posits of asbestos fibers in the settling areas of the systems.
The fate of the asbestos in coating and paint compounds that would usually
be scrapped during replacement and demolition of the equipment to which they
are applied, varies with the product. Steel equipment, structures, piping,
and other metallic materials with asbestos coatings are usually fed to scrap
yards and recovery furnaces where the asbestos ends up in the slag produced
by such operations. Asbestos fibers from demolished concrete and other non-
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recoverable materials usually end up in landfill dumps or incineration opera-
tions. Asbestos could possibly be released in the combustion gases or the
ashes of the incineration process if temperatures were not controlled.
Scrubbers can control the loss from combustion gases, transferring it to a wet
waste product to be dealt with. If the asbestos in the product is not destroyed
during incineration, it could be released instead in the ashes, which are
sometimes used in fertilization applications or in making cement blocks.2
The total quantity of asbestos released as scrap approximates the balance
of annual consumption after a 1-percent reduction is taken for losses in
application, 1 to 2 percent consumed for expanding uses, and 25 percent for
maintenance uses. This amounts to about 70 percent or 7950 m.t. per year.
Approximately 5675 m.t. of this goes to landfill dumps, and the balance
(2275 m.t.) goes to scrap recovery furnaces.2 A summary of these various des-
tinations of asbestos fibers is included in Table 50. These figures are based
on the 1980 consumption rate. This does not allow for the backlog that may
prevail from earlier consumption at even higher rates. Not only will these
past liigh consumption rates tend to increase the scrap rate for the near
future, they will also increase the overall deposition of asbestos in our
living environment.
. CONCLUSION
Neither the U.S. Bureau of Mines nor the U.S. Bureau of Census reports
contain data by which consumption trends for asbestos sealant products can be
estimated. Previous discussions with suppliers and consumers of such products
indicate that they differ considerably in their predictions with respect to
future applications of asbestos in these products.2 As mentioned, some
suppliers have already stopped using asbestos as a result of the recent OSHA
regulations. Others, however, use it at essentially the same or even higher
rates. An extensive reduction in use has taken place to arrive at the current
level, but it is expected that this level will hold due to the fact that in nearly
all coating applications, the asbestos is completely encased. It is even
predicted that new uses and products will appear in this category as the use
of short fiber California asbestos is implemented in the manufacturing process.2
As for specific roofing products, industry spokespersons indicate that
asbestos coatings are undergoing static growth, and this area may be one in
which there are small decreases.
Looking at industry considerations, there are several conditions that need
to be met to help improve the present situation. Improved packaging methods
for bulk asbestos shipments are pointed out as having high priority.17 Such
items as recyclable bulk containers, enclosed pallets to shield bags from
physical damage and reinforced bags are needed. Automatic bag-opening machines
would eliminate manual operation, which is where the majority of fiber in-
troduction takes place. If it can be assured that such activities as bag
opening operations can be performed in new ways with minimal fiber release
to the plant environment.
202
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TABLE 50. APPROXIMATION OF ASBESTOS RLEASED TO ENVIRONMENT FROM
COATING AND PAINTING COMPOUND APPLICATIONS2
Source
Disposition
Metric tons
per year
Waste during application
To
sewer system or landfills
115
Losses from water,
weathering, and service
To
sewer system or ground
waters
2,835
Scrap from replacement
and demolition
To
scrap metal recovery
furnaces
2,275
To
landfill and incineration
Total release
5,675
10'90°a
Nearly all of the asbestos released in the above figures is bound
versus free-fiber form.
203
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REFERENCES
1. Clifton, R. A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of
Mines', Washington, D.C.
2. Meylan, W. M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination:
Task III - Asbestos. EPA 560/6-78-005. August 1978.
3. Telecon. N. R. Fernandez, Celotex Corp., with David Cook, GCA. January
29, 1980. Asbestos in roofing materials.
4. Telecon. Edmund Fenner, Johns-Manville, with David Cook, GCA. January
15, 1980. Asbestos in various sealant products.
5. Telecon. Ken Brzozowski, TREMCO, Inc., with David Cook, GCA. January
18, 1980. Substitute fibers for roofing products.
6. Telecon. Fred Mallay, Consolidated Protective Coatings Corp., with
David Cook, GCA. January 18, 1980. Substitutes for roofing products.
7. Telecon. Jack H. Engel, Chrysler Corp., with David Cook, GCA. January
17, 1980. Asbestos in automobile undercoatings.
8. M. Grayson, and D. Eckroth. Encyclopedia of Chemical Technology, Third
Edition, Volume 6. Wiley-Interscience. New York, N.Y. 1978. p. 461.
9. Telecon. T. Dudick, Dudick Corrosion-Proof Manufacturing, Inc., with
David Cook, GCA. January 18, 1980. Acid and alkali resistant coatings.
10. Telecon. Ken Heffner, Electro Chemical Engineering and Manufacturing
Co., with David Cook, GCA. January 18, 1980. Asbestos containing
mastics.
11. Telecon. Jack Fleming, Bondex International, with David Cook, GCA.
January 16, 1980. Texture paints.
12. Telecon. Pass, Williams, Synkoloid Co. with David Cook, GCA. January
16, 1980. Texture paints.
13. Telecon. Charles Spector, Everseal Manufacturing Co., Inc., with David
Cook, GCA. January 17, 1980. Texture paints.
204
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14. Telecon. Harry Schwartz, Baltimore Paint and Coatings Group of Dutch Boy
Paints with David Cook, GCA. January 22, 1980. Texture paints.
15. LaShoto, Paul W. Trip Report on visit to Celotex Corp., Lockland, OH.
August 1, 1979.
16. Gregg, R. T. Development Document of Effluent Limitations Guidelines
and New Source Performance Standards for the Textile, Friction Materials
and Sealing Devices Segment of the Asbestos Manufacturing Point Source
Category. U.S. National Technical Information Service, PB-240-860.
December 1974.
17. 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.
18. W. E. Davis and Assoc. (Leawood, KS). National Inventory of Sources and
Emissions: Asbestos - 1968. U.S. Environmental Protection Agency
Office of Air and Water Programs OAQPS, Research Triangle Park, NC.
APTD-70, February 1980.
19. 1975 Thomas Register.
20. Levine, R., Ed. Asbestos: An Information Resource. May 1978.
21. Harwood, C. F. et al. Asbestos Emissions from Baghouse Controlled
Sources. American Industrial Hygiene Association Journal. August
1975, pp. 595-603.
205
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SECTION 11
ASBESTOS-REINFORCED PLASTICS
INTRODUCTION
Asbestos fibers, when added to polymeric materials, modify the physical and
chemical characteristics of the composite. Fibers, in general, function as both
fillers and reinforcing agents. The advantages of using asbestos derive from
the fact that asbestos combines the advantages of both a mineral and a fibrous
binder carrier with reinforcing action.
Asbestos fibers have been used in combination with plastics since the
1920's when asphalt floor tiles were first introduced. For most of the history
of asbestos plastics, the largest quantity of asbestos fiber employed consisted
of the shorter grades that functioned primarily as fillers rather than rein-
forcing fibers. This is still true today. However, recent research efforts
have been directed toward using longer grade, reinforcing asbestos fibers.
The plastic materials manufacturers using bulk or "loose" asbestos fiber,
typically in molding compounds, are the subject of this section. Industries
which utilize asbestos in conjunction with plastics and other ingredients such
as floor tile, friction materials, and gasketing, are discussed in other sec-
tions of this report. Also, in defining the scope of products to be discussed
in this section, any asbestos plastic material that employs asbestos fiber in
a preprocessed form such as paper, mat, felt, roving or cloth has been con-
sidered a secondary product for other asbestos industry segments such as paper
and textiles and is therefore addressed in other sections of this report.
The material presented in this section is a summary of existing published
data augmented with information obtained by telephone questionnaires and from
observations and discussions with manufacturing personnel at operating facili-
ties producing asbestos-reinforced plastics. Information was collected while
visiting two facilities producing asbestos-reinforced plastics. Although an
attempt was made to obtain extensive fiber release data, limited quantitative
data were available.
PRODUCT DESCRIPTION
Composition—
Bulk fiber is the most widely used form of asbestos in combination with
plastics. A breakdown of the various asbestos types and grades used in bulk
by primary plastics manufacturers in 1980 is given in Table 51. Chrysotile
206
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is used in the largest quantities in plastics for molding compounds with
lesser amounts of crocidolite. Chrysotile classified according to the Quebec
Asbestos Mining Association (QAMA) test in grades 1 through 5 is normally
used for its reinforcing properties. Grade 7 chrysotile fibers are used for
their thixotropic characteristics (to control flow), heat resistance, dimen-
sional stability and low cost. The crocidolite variety of asbestos is uti-
lized for specialty purposes where corrosion resistance is important.
TABLE 51. ASBESTOS USE BY TYPE AND GRADE IN 19801
Asbestos type
Consumption
(metric tons)
Chrysotile grade 1
and 2
200
5
400
7
800
Crocidolite
100
Total
1500
Because of desirable properties such as thermal and mechanical enhance-
ment and dimensional stability, asbestos fibers have traditionally been used
in a wide variety of plastic resins—including phenolic, vinyl, epoxy, un-
saturated polyester, urea diallyl phthalate, polypropylene, nylon and thermo-
plastic polyester (PBT).2 Table 52 presents some of the effects of asbestos
on physical properties of plastics.
TABLE 52. TYPICAL CHANGES IN RESIN PROPERTIES WITH
ASBESTOS REINFORCEMENT3>a
% change
Material
Flexural
modulus
Flexural
strength
Tensile
strength
Impact
notched
izod
HDT
(°F)
ABS
+130
-20
-5
-60
+16
Nylon 6
+170
+100
+85
+20
+200
Phenolic
+120
+50
-
+5
-
Polyethylene
+320
+30
+20
0
+72
Polyphenylene
sulfide
+60
+100
+10
+100
+35
Polypropylene
+360
-
-4
+125
+25
Polystyrene
+110
+50
+20
-40
+18
Optimum reinforcement usually requires 20 to 40 percent short fiber
asbestos.
207
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Uses and Applications—
Despite a recent trend to use substitute materials, asbestos-reinforced
plastic molding compounds are used in a variety of applications including the
electrical, electronic, automotive, and printing industries. For example,
the Rogers Corporation, a large manufacturer of phenolic molding compounds,
uses asbestos in the following products: asbestos-reinforced board material
used in the printing industry as a matrix from which multiple rubber or plas-
tic printing plates can be molded; automotive transmission reactors which are
employed to direct the flow of transmission fluid; commutators for electrical
motors, switches and circuit breakers. ** General Motors, a major consumer
of reinforced plastics, uses Rogers Corporation asbestos-reinforced molded
commutators used in fan drive motors installed in its new 1980 front wheel
drive (X-model) compacts.**
Special Qualities—
Asbestos fibers are used to reinforce both thermosetting polymers such
as phenolic and modified phenolic resins, epoxy resins, silicones, polyesters
and diallyl phthalate polymers, and thermoplastic polymers such as vinyl
resins, polypropylene, and fluorocarbon polymers.
Asbestos is particularly useful in molding compounds because, in addition
to its reinforcing properties, it will impart very good surface finish, tough-
ness, resistance to heat and fire, and less shrinkage and warpage than other
fibers.5 Also, the addition of asbestos improves the handleability of the
product during processing. For example, putty-like compounds become much
less sticky.
The advantages of using asbestos instead of inorganic or organic fillers
(rock dust, wood floor, cellulose products, etc.) derive from the fact that
asbestos has both the advantage of a mineral and a fibrous binder carrier
with reinforcing action, and these favorable characteristics are revealed in
the corresponding properties of the asbestos molded articles. When unpro-
cessed asbestos fibers are employed, the properties of the molded articles
reflect the length of the fibers, the degree to which the bundles of fibers
have been opened, and the degree of purity of the fibers.6
SUBSTITUTES
A wide variety of alternatives to asbestos fibers are available as rein-
forcements and fillers in plastics. Manufacturers have developed alternatives
for a majority of products previously reinforced with asbestos in which the
physical properties of the substitute product are close to or may even exceed
the asbestos product they replace. New fiber technology has been developed
which has boosted physical properties of substitutes such that they are com-
parable to asbestos. In addition, manufacturers have blended various fillers
and reinforcing materials to achieve required properties. Although there are
still some specialty products where no feasible asbestos substitutes have been
found, in general, reinforced plastics appear to have progressed towards the
replacement of asbestos. A summary description of substitute materials is
provided in Table 53.
208
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TABLE 53. ASBESTOS SUBSTITUTE MATERIALS7'8
Substitute
material
Performance and comments
Fibrous glass
Clay
Talc
Mica
Carbon fibers
Aramid fibers
Polyethylene
fibers
Calcium sulfate
Wollastonite
Processed mineral
fiber
May be used for higher temperature appli-
cations; new glass fiber technology en-
hances the physical properties of the ma-
terial; problems with abrasiveness of glass
wearing out processing equipment; process
change probable.
Used as filler, no reinforcement; new
clay base compositions are reported
to maintain the acceptable balance of
heat resistance and impact strength.
Loss of strength but can compensate
by making thicker walled product;
presently used as an asbestos sub-
stitute; limited to 450°F
applications.
Adds dimensional stability and in-
creases strength of plastics; high
aspect-ratio mica purported to pro-
vide middle ground in cost perfor-
mance between inorganic particulate
fillers and fiber reinforcement;
blended with higher priced substitute
materials.
For high strength applications; in-
creases acid resistance in phenolics;
also used as filler for thermoset
plastics; high heat resistance;
specialty applications only.
Use in specialty plastic reinforce-
ments; too expensive for asbestos
replacement in phenolic molding
compounds; can be blended with less
expensive materials.
Still in development stage; high
modulus but poor heat resistance
properties.
Provides improved output rates,
allows high loadings, and results
in low densities; high heat resis-
tance; no reinforcing properties.
Asbestos replacement in phenolics. Has
been classified as merely a nuisance dust.
Asbestos replacement in phenolics and epoxy
gel coats.
209
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MANUFACTURING
The manufacture of asbestos-reinforced plastic products can be divided
into two segments. A small number of primary manufacturers (currently there
are only five manufacturers of asbestos molding compounds—see Table 54)
produce molding compounds in pellet or flake form, package it, and sell this
granulated material to up to perhaps 5,000 separate secondary manufacturers
where the final product is shaped and finished. The primary manufacturing
steps typically consist of (1) fiber receiving and storage, (2) fiber intro-
duction, (3) dry blending, (4) resin formation, and (5) packaging and ship-
ping. The secondary manufacturing steps usually are at a facility remote
from the primary processing and consist of (1) resin receiving and storage,
(2) resin introduction, (3) forming, (4) curing, (5) finishing, and (6) prod-
uct packaging and shipping to consumers. The major secondary manufacturers
of asbestos-reinforced plastic molding compounds produce products for the
electrical, electronic, automotive and printing industries. It is the opinion
of some manufacturers that the combination of high strength, corrosion resis-
tance, high temperature performance, and low price provided by asbestos
cannot be sacrificed.
TABLE 54. PRIMARY MANUFACTURERS OF PHENOLIC
MOLDING COMPOUNDS13'7,9,a
Plant name
Location
Plaslok Corp.
Buffalo, NY
Plastics Engineering
Sheboygan, WI
Reichold Chemicals
Elizabeth, NJ
Resinoid Engineering
Skokie, IL
LaPorte, IN
Newark, OH
Rogers Corporation
Manchester, CT
Augmented by GCA telephone contact.
Primary Manufacturing
Figure 26 illustrates the general process flow for the primary and
secondary manufacture of asbestos-reinforced plastics.
Asbestos fiber is typically transported in a dry state by railcar or
truck and is contained in palletized paper or plastic bags. A recent trend
has been towards employing shrink-wrapped pallets which is now a customer
option. At the plant, this material is unloaded either manually or by
powered fork-lift trucks and transported to a raw-fiber warehouse for inter-
mediate storage. At most facilities housekeeping practices such as taping
broken bags and vacuuming the trucks or railcars prior to unloading are
employed. The asbestos fiber is usually not isolated but stored in the same
open warehouse with other materials such as dry resin and fillers. The ware-
house air may or may not be exhausted to a particulate collection device.
210
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PRIMARY
MANUFACTURING
FIBER INTRODUCTION
RESIN FORMATION
DRY BLENDING
FIBER RECEIVING
AND STORAGE
RESIN PACKAGING
AND SHIPPING
SECONDARY
MANUFACTURIN6
RESIN INTRODUCTION
PRODUCT FINISHING
PRODUCT CURING
PRODUCT FORMING
PRODUCT PACKAGING
AND SHIPPING
RESIN RECEIVING
AND STORAGE
CONSUMER
Figure 26. General process flow for manufacture of asbestos-
reinforced plastic.9
211
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The raw fibers are transported on pallets by fork-lift trucks to staging
areas within the plant near the fiber introduction work stations. The as-
bestos fibers are introduced to a dry blending step which involves mixing
the dry ingredients necessary to compound the material. Dry blending is
needed to achieve a homogeneous mixture of the ingredients which include
asbestos fiber, catalysts, additives, resins, and polymers. A wide variety
of equipment is used throughout the industry to ensure a low-shear, well-
mixed blend.
Asbestos fibers may be introduced into the process in a number of ways.
At smaller facilities, preweighed asbestos is conveyed to a storage hopper
prior to charging to the dry blending equipment. Alternatively, asbestos
may be charged directly into the blending machinery without intermediate
storage or handling. To protect the dry ingredients from excessive abrasion,
mechanical agitation is minimized during blending.
At larger facilities, the blending step may be preceded by a beater
operation where raw fibers are broken up and sized. Since the beating process
is vigorous, pulpable bags can be used.10 After conditioning, the asbestos
fibers are transported to the product mixers pneumatically or in sealed
containers.
Dust control measures during fiber introduction and blending include
local exhaust hooding, evacuated enclosures, and vacuum lines. All of these
devices typically vent through enclosed ductwork to cyclones or fabric fil-
ters. Fabric filters are known to have particulate removal efficiencies of
99 percent.
Asbestos shipping wrappers that are not charged into the mixer along
with the fibers are placed in bulk sacks affixed with asbestos warning
labels. When full, the sacks are sealed and taken to a landfill. House-
keeping practices around the fiber introduction area include central vacuum
cleaning systems and mechanical floor sweepers.^
After the individual ingredients have been thoroughly mixed, the blend
is transferred via sealed containers or vacuum conveyors to resin formation
equipment. A variety of equipment may be involved, depending upon the end-
product specifications. In general, the resin is formed by either of two
processes: externally heated extrusion or internally heated (friction/shear)
Banbury mixing. Both processes produce pellets, powders, or some similar
product which is sometimes called a "preform." This resin is drummed and
used in subsequent processes to form the end product. Some of the primary
industries fabricate their own plastic products, but it is estimated that
approximately 70 percent of the asbestos reinforced plastics are sold to
secondary fabricators. Dust-control equipment in general use includes
exhaust hoods vented to fabric filters and partial enclosures of process
equipment. Housekeeping and maintenance include central vacuum cleaning
systems and mobile floor sweeping/vacuuming equipment. In general, all the
material collected by fabric filters and housekeeping systems is bagged,
212
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sealed, and tagged with special asbestos warning labels before being trans-
ferred to a landfill. At some facilities employing a beater operation, a
portion of accumulated fines is wetted and recycled to the beaters.
Secondary Manufacturing
Subsequent processing of asbestos-reinforced plastics may be accomplished
at a remote location or at the same facility where the primary manufacturing
is performed.
At remote locations, drummed "preform" is received by railcar or truck
and is transferred to a storage area by fork-lift truck. The drums are sub-
sequently moved to the forming step. The forming step involves actual forma-
tion of an end product from the preformed resin by remelting the preform
and submitting it to rolling, stamping, pressing, or molding. The processing
equipment varies throughout the industry. Remelting serves to start the
polymerization, cross-linking, and thermosetting reactions. Dust-control
equipment includes exhaust hoods to fabric filters and partial enclosure of
process equipment. Housekeeping practices include central vacuum cleaning
systems and mobile floor sweeping/vacuuming equipment.
Following the molding process, the formed product is transferred to the
curing step which involves control of cross-linking and thermosetting re-
actions to achieve specific strength and stiffness characteristics. This
normally requires an enclosed area, furnished with a ventilating system.
When the processes employ air-curing, hoods and local enclosures are provided.
Housekeeping procedures are similar to those employed in other steps of dry
processing.
After the product is cured, it is finished. This involves sawing, grind-
ing, drilling, machining, etc. The degree of finishing and the type of process
used depends upon the end use of the product. Asbestos dust is released when
the plastic products are finished. Hand and portable tools are normally
supplied with local exhaust systems vented through a central fabric filter
unit. Larger, stationary machines employ local exhausts near the surface being
finished and, in some cases, are supplemented with hoods over the finishing
machine itself. All exhausts are vented to fabric filters. Housekeeping
practices include central vacuum cleaning systems and mobile floor sweeping/
vacuuming equipment.11
In general, all the material collected by fabric filters and housekeeping
systems is bagged, sealed, and tagged with special asbestos warning labels
before being transferred to a landfill.
It is extremely difficult to determine the entire scope of the secondary
market for asbestos-reinforced plastics from primary molding compounds. There
are industry estimates of some 3,000 secondary fabricators of reinforced
plastics and perhaps 5,000 separate end users of the product. It is impossible
to determine what percentage of these plastic fabricators presently use
asbestos-reinforced plastics. It has been reported, however, that many secon-
dary manufacturers have preferred not to process compounds containing asbestos
fibers in their operations and have already converted to asbestos-free compounds.
213
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Manufacturing Plants
The most important primary manufacturers of phenolic molding compounds
which currently produce asbestos-filled compounds are listed in Table 54.
Production Volumes
In 1978, 4,900 metric tons of asbestos fiber were consumed in the pro-
duction of asbestos plastic molding compounds as classified by the Bureau of
Mines.^ In 1980, however, the Bureau of Mines reported that only 1,500 metric
tons of asbestos were used in the production of plastics in the United States.*
This 69 percent decline compared to a 42 percent decline in overall asbestos
use reflects a dramatic trend toward the use of substitute fibers.
ASBESTOS RELEASE
Input-Output
Although Connecticut State personnel^ measured significant atmospheric
fiber concentrations in the vicinity of phenolic molding compound manufacturing
operations, Levine^ has estimated process-related air emissions from plastic
manufacturing to be minimal. Figure 27 shows estimated process disposal and
emissions for the plastics manufacturing industry based on Levine's"Cb 1974
estimates projected to 1980 U.S. Bureau of Mines consumption figures. Of the
1,500 metric tons entering the process as raw asbestos fiber, approximately
1,462 metric tons are contained in the final product and 38 metric tons are
sent to disposal as vacuum cleaner and baghouse dust and product scrap. It
is estimated the asbestos fiber emission from control equipment (typically a
baghouse) is minimal. Levine's atmospheric emission estimates are based on
gross assumptions with a reported uncertainty of at least an order of magnitude.
Meylan^ reports emissions of 1 to 3 orders of magnitude less. GCA's estimate
of atmospheric emissions from disposal is based on Levine's^ data and takes
into account the amended Asbestos NESHAP's regulations adopted in 1975 regard-
ing the disposal of asbestos-containing wastes.17
During Manufacture
Workplace Exposure—
Based on data collected by the Asbestos Information Association from
plants covering 55 percent of the asbestos-reinforced plastics industry,
Table 55 has been compiled. The high exposures for receiving and storage
are due to bag breakage during handling. The high exposures for fiber in-
troduction are a result of a prevalence of manual bag opening, emptying, and
handling for disposal.11
214
/
-------
MANUFACTURING OPERATIONS
RAW
ASBEST03
FIBER
RECEIVING
ANO
STORAGE
CONSUMER
1 ,500 TPY
VACUUMED
DUST
BAGHOUSE
LEGEND
input/output
BAGHOUSE
^EMISSIONS
manufacturing operations
control equipment
SOLID
WASTE
DISPOSAL
t imate deposi1 ion
EM ISSIONS
EMISSIONS
0.1 TPY
so) id
water
01SPOSAL
PRODUCT
CUR ING
PRODUCT
DRY
BLENDING
FIBER
INTRODUCTION
SECONDARY
MANUFACTURING
38 TPY 0.I TPY
^MINIMAL AMOUNTS
Figure 27.
Process and disposal emissions from asbestos plastics industry (metric tons).
-------
TABLE 55. TIME-WEIGHTED AVERAGE FIBER COUNTS3, -
ASBESTOS-REINFORCED PLASTICS11
Fiber count with existing
control technology
Process step
Typical
fibers/cc
Range
fibers/cc
1.
Fiber receiving and storage
1.0
0.25-2.5
2.
Fiber introduction
2.0
0.5 -3.0
3.
Dry blending
1.0
0.2 -1.5
4.
Resin formation
0.75
0.5 -1.5
5.
Kneading, rolling, etc.
1.0
0.25-1.5
6.
Cure
0.75
0.2 -1.5
7.
Finishing
1.0
0.5 -1.5
^IOSH method, counting fibers >5 ym by phase contrast
microscopy.
The asbestos dust exposure in other steps arises from the handling and
introduction of the dry blended mixture and the dry preform. After remelt-
ing, the asbestos is bound in the polymer matrix.
Normally, only minor finishing is provided for the cured product. Thus,
the amount of asbestos fiber released is less than in other asbestos industries.
Additionally, the content of asbestos in the product is low compared to such
products as asbestos-cement pipe or sheet. Therefore, for the same degree
of finishing, a lower asbestos fiber release is expected as the content of
asbestos in the product is decreased.11
From the exposure data given in Table 55 for fiber receiving and storage
(0.25 to 2.5 f/cc), spillage from raw-fiber containers may add significantly
to worker exposure levels and subsequent plant air emissions. Several cur-
rently available practices and techniques are used to avoid asbestos bag
damage. The controls include the use of inflatable dunnage, lined railcars,
shrink-wrapped pallets, and double-sealed bags. Taping of broken bags com-
bined with prompt vacuuming of all spills also reduces asbestos dust emissions
to the air in receiving and warehouse areas. The use of air pollution control
equipment for existing warehouse exhaust is inappropriate due to the cost of
designing for the typical large volumes of air. More controlled receiving
and warehouse areas for asbestos with exhaust vented to pollution control
equipment may be possible. Such modifications, however, might prove costly.
At most asbestos reinforced-plastic manufacturing plants, where prepro-
cessed (opened and sized) fibers are purchased, the fiber-introduction step
is accomplished largely by the use of evacuated (to a fabric filter), hooded
dump stations with enclosed empty bag receptacles contiguous to the dumping
216
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hoods. Pulpable bags are not used since the dry blending step is accomplished
by gentle agitation which would not break down the bag sufficiently. Due to
the relatively high workplace exposure fiber count (0.5 to 3.0 f/cc), the
fiber introduction step is one of the largest generators of airborne asbestos
fibers in the primary asbestos-reinforced plastics industry. However, since
the processing areas are usually hooded and vented to fabric filters, the dust
emitted to the atmosphere is due to either the escape through the fabric filter
or inefficiencies in the hood collection system.
During the dry blending and resin formation processes, most airborne
asbestos fiber emissions are generated during transfer of the dry product.
Localized ventilating systems exhausted to fabric filters and partially
enclosed process equipment reduce the asbestos fiber emissions to the atmo-
sphere. As in the fiber introduction step, the airborne dust emitted to the
outside environment is due to either the escape through the fabric filter or
inefficiencies in the hood capture system. The preform, which is the product
from the resin formation step, is typically in pellet or flake form. There-
fore, the potential for dust generation is present throughout the entire
primary manufacturing sector. Since the preform is drummed for shipment to
secondary manufacturers, vent systems and enclosed process equipment are
employed in the packaging area to reduce airborne emissions.
Emissions to Air—
Data concerning asbestos air emissions from primary manufacturing of
asbestos-reinforced plastics is very limited.^ Ambient air asbestos levels in
the vicinity of one primary manufacturer of phenolic molding compounds have
been measured and these levels give an indication of plant emissions. The
manufacturer in question uses approximately 150 m.t./month of chrysotile
asbestos.*5 Thirty-day average ambient levels near the plant measured from
3 to 33 ng/m-* of asbestos.15 The highest reading, 33 ng/m^, exceeded the
proposed state (in which this manufacturer is located) air quality standard
for asbestos of 30 ng/m^ or 30,000 total asbestos fibers/m^, 30-day average.
All processes with a potential to emit asbestos fibers at the facility were
well controlled, with hoods and baghouses used to minimize asbestos fiber
release. The ambient monitoring data indicate that asbestos emissions from
a phenolic molding manufacturer can be significant in the immediate vicinity
of the facility, in spite of good control practices.
The principal sources of airborne asbestos fiber emissions in the primary
and secondary reinforced plastics industry are the finishing operations. Once
the asbestos fibers are encapsulated by the plastic resins, they can only become
airborne if the fiber bundles are penetrated by a cutting tool such as a drill
or a saw. Most hand and portable finishing tools and primary and secondary
facilities are supplied with local exhaust systems connected to the central
ventilation/collection system. These local exhaust systems can be designed
to minimize any asbestos fiber release to the workplace and subsequently to
the atmosphere. Therefore ambient emissions from plastics manufacturing
would mainly be asbestos fibers which escape through the central fabric fil-
ters. ^ Based on 1980 asbestos consumption, these emissions are estimated to
total less than 0.02 m.t. per year. This estimate is based on monitoring
data of well-operated baghouses. It should be noted that faulty baghouse
equipment can potentially increase emissions significantly.
217
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Release to Water—
Water is not used directly in the manufacture of asbestos-reinforced
plastics. Asbestos would be released in wastewaters from water-type air
scrubbers used to clean exhaust from hooded processing steps. However, bag-
house collectors are normally used for this function.
Release to Land—
The asbestos solid waste generated at primary manufacturing facilities
is mostly from baghouse collections and housekeeping procedures or is con-
tained in the emptied raw asbestos bags discarded in the fiber introduction
step. Pellet and flake product scraps can normally be recycled. At one
manufacturing plant where a beater operation is run, the accumulated fines
from baghouses are wetted for reuse in the beater.^0 Some facilities recycle
baghouse collections as a filler material. However, many plants find it
more economical to dispose of baghouse and housekeeping collections along
with empty raw asbestos bags in bulk sacks, specially marked with warning
labels, prior to shipment to a landfill.
The amount of asbestos removed to landfills from primary manufacturing
is difficult to determine. The disposal estimate presented in this section,
38 metric tons/year, includes both primary and secondary manufacturing
although most of this scrap is from secondary producers. This total amounts
to 2.5 percent of industry asbestos use. It was based on Levine's disposal
estimates projected to 1980 asbestos consumption data. These data are more
conservative than estimates published by Meylan, et al.y Meylan has estimated
that solid waste generated at secondary manufacturing facilities in the form
of product scraps and damaged products amounts to about 2 percent of annual
use, while an additional 4 percent is collected in baghouses. This total of
6 percent scrap asbestos amounts to approximately 90 metric tons of solid
asbestos waste based on 1980 industry asbestos consumption. Insufficient
information exists relative to the amount of scrap generated, scrap asbestos
content and current disposal practices at both primary and secondary plastics
manufacturing facilities to determine which estimate is correct. Since the
Levine estimate is more conservative in predicting overall asbestos emissions,
it is the one presented here.
During Use
Fiber release is unlikely during the service life of an asbestos plastic
product. Matrix bonding binds the fibers so that only friction, scraping,
sanding, rubbing, or some other force which can break down the plastic matrix
will result in free fiber release. Typical uses for asbestos reinforced
plastic, such as in electrical equipment, would not subject the plastic to
these forces.
During Disposal
In general, most of the diversified plastic products are not designed
to have a service life greatly in excess of 10 years. Therefore, a sizeable
percentage of production (perhaps 80 to 90 percent) is intended for replace-
ment purposes.9 The annual wasting of asbestos plastics may, therefore,
be in the range of 1,300 m.t. These wastes will be discarded primarily at
218
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commercial landfills and auto junkyards (asbestos plastics have significant
usage in automobiles). Because the asbestos fibers are encased in the plastic
matrix, the replacement wasting of asbestos-reinforced plastics is not judged
to cause any significant free-fiber release to the atmosphere.
CONCLUSIONS
Through the 1970s there has been a consistent decline in the use of
asbestos for reinforced plastics. This decline in overall asbestos use
7 1 ft
reflects a dramatic trend toward the use of substitute fibers. ' Manufac-
turers have reported that customers have demanded asbestos-free compounds.13,19
Coupled with customer demand are the high costs of complying with environmen-
tal regulations. Installation of engineering controls and implementation of
specific work practices have reduced the economic advantage of manufacturing
asbestos-based plastic resins. The increased costs have had the greatest im-
pact in industries where asbestos was being used mainly because it was inex-
pensive and where the properties imparted to the plastic by asbestos fibers
were not critical to the usefulness of the product. The major manufacturers
of reinforced plastics are either in the process, or have already phased
out asbestos in their product lines. However, there are apparently some
specialty product lines where no feasible asbestos substitute has been found.
It may be that asbestos will remain a reinforcement material in specialty
applications, if exposures can be controlled to within acceptable limits.
In general, the control of asbestos fiber emissions from manufacture of
asbestos-reinforced plastics is accomplished about as well as can be reasonably
expected with today's technology. The major sources of airborne emissions are
at fiber receiving and storage and fiber introduction during primary manufactur-
ing, at the finishing step during secondary manufacturing, and from reentrainment
of improperly discarded solid waste at dumps and landfills. At the manufac-
turing facilities, most equipment is hooded and exhausted to fabric filters
and residual dust is continuously removed by vacuuming during housekeeping.
The problem at landfills is being alleviated by specially tagged containers
holding asbestos and monitoring their disposal.
Solid waste is generated from baghouse and housekeeping collections and
from product scraps. The latter is not a large problem in the primary in-
dustry segment because most scraps are recyclable. In the secondary industry
segment, upwards of 38 tons of asbestos annually end up in product scraps
which are removed to landfill. However, the asbestos in these scraps is bound
tightly in the plastic matrix and free-fiber emissions would not be expected.
Asbestos fibers should not be released during the service life of asbestos-
reinforced plastic molding compounds because the products are not typically
subjected to friction, scraping, sanding, rubbing, or some other physical force
that could break down the plastic matrix. The product life expectancy is
usually short (less than 10 years). The wasted material is disposed primarily
to commercial landfills and auto junkyards.
219
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It can be concluded that most of the asbestos fibers used for reinforced-
plastic molding compounds since their invention in the early 1920s have been
discarded with waste products in dumps and landfills in a nonfriable form.
It can also be concluded that asbestos used for plastics will hold a smaller
and smaller fraction of the reinforced plastics market.
220
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REFERENCES
1. Clifton, R. A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of
Mines, Washington, D.C.
2. Naitove, M. Asbestos in Plastics: Looking for Alternatives. Paper
presented at the National Workshop on Substitutes for Asbestos,
Arlington, Va. July 14-16, 1980. U.S. EPA Report No. EAP-560/3-80-001.
November 1980.
3. Byrne, Jr., R. E. Asbestos. Union Carbide Corp. brochure reprinted
by permission from the Modern Plastics Encyclopedia, McGraw-Hill Inc.
4. Exner, P. Trip Report to Rogers Corporation, Manchester, Conn.,
GCA, October 30, 1979.
5. Oleesky, S. S., and J. G. Mohr. Handbook of Reinforced Plastics.
Reinhold. 1964.
6. Berger, H. Asbestos with Plastics and Rubber. Chemical Publishing
Co., Inc. New York, N.Y. 1966.
7. Wright, M., et al. Asbestos Dust Technological Feasibility Assess-
ment and Economic Impact Analysis of the Proposed Federal Occupational
Standard - Part I: Technological Feasibility Assessment and Economic
Impact Analysis, prepared by Research Triangle Institute, for U.S.
Department of Labor, OSHA, Washington, D.C. September 1978.
8. Telecon. Vincent R. Landi, Rogers Corporation with R. Bell, GCA
Corporation/Technology Division. February 5, 1980.
9. Meylan, W. M., et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination:
Task III - Asbestos. EPA 560/6-78-005. August 1978.
10. MacBride, R. R. Plastiscope 1. Modern Plastics. September 1976.
p. 12.
11. Daly, A. R., et al. Technological Feasibility and Economic Impact of
OSHA Proposed Revision of the Asbestos Standard (Construction Excluded).
Asbestos Information Association/North America. March 26, 1976.
12. Swanson, R. C. Sales Representative, Colt Industries, Garlock Inc.
Mechanical Packing Division. Charlotte, N.C. Meeting with Mr. T. Curtin,
GCA Corporation, February 21, 1980.
221
-------
13. The Asbestos Controversy Continues, Plastics Design Forum.
November/December 1978.
14. Clifton, R. A. Asbestos in 1978, Mineral Industry Surveys. U.S. Bureau
of Mines, Washington, D.C. August 22, 1979.
15. Bruckman, L., R. A. Rubino. Monitoring Asbestos Concentrations in
Connecticut. Air Pollut Contr Assoc J. 28(12). 1978.
16. Levine, R., ed. Asbestos: An Information Resource. May 1978.
17. 40 CFR Part 61, Subpart B - National Emission Standards for Hazardous
Air Pollutants - Asbestos.
18. Telecon. Sales Manager, General Electric Co., with R. Bell, GCA Cor-
poration, February 1980.
19. A. S. W. More Muscle, Higher Heat: They Power a Phenolic Molding
Compound 'Revival.1 Modern Plastics. July 1979.
222
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SECTION 12
TEXTILES
INTRODUCTION
Asbestos, the only mineral that can be processed into textiles using
looms and other equipment commonly employed in the textile industry, is used
to manufacture durable heat and acid resistant textiles. Final products take
many forms, such as roving, lap, yarn, cord, cloth, tubing, wick and tape,
and are used in many applications such as friction materials, industrial packings,
electrical insulation, and thermal insulation. Asbestos has been used in fire
and heat resistant textiles since antiquity. Modern commercial operations
have been well established for over a hundred years.1
In 1980, approximately 1,900 metric tons of asbestos or about 0.5 per-
cent of the total U.S. fiber consumption went into textiles.2 This represents
a decline of almost 67 percent from the amount processed into textiles in
1979.3 The number of plants producing asbestos textiles has also declined
over the last few years. Thirty-five plants produced asbestos textiles in
19681* and at least 13 plants produced asbestos textiles in 1972. 5 But as of
1976 only six plants owned by four firms are known to manufacture asbestos
textiles.6 In 1976, 65 percent of the nation's demand for asbestos textiles
was supplied domestically, with imports accounting for the remainder.7 It
is assumed this percentage has not changed.
PRODUCT DESCRIPTION
Composition
Asbestos textiles are predominantly made from long, spinning grade
chrysotile fibers. Grades 1, 2 and 3 are used, with grade 3 accounting for
90 percent of the asbestos fiber in textiles produced in 1980.2 The dif-
ferent forms of asbestos textiles manufactured and the six major product
categories in which they are used are presented in Table 56. The asbestos
content of textiles ranges from 75 to 100 percent by weight.8'9
Asbestos yarn is composed primarily of asbestos fibers. Cotton, nylon,
polyester, and wire are added for reinforcement in some applications of yarns.
Asbestos yarns are made in all of the standard ASTM grades shown in Table 57.
223
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TABLE 56. FORMS OK ASBESTOS TEXTILES USED IN ASBESTOS PRODUCTS
Packings
Fire
resistant
Thermal
insulation
Electrical
insulation
and
gaskets
Friction Specialty
materials textiles
Yarn
Yarn
Yarn
Yarn
Yarn Fiber
Thread
Cloth
Roving
Rope
Cloth
Cloth
Cord
Tape
Wick
Rope
Thread
Cord
Tape
Felts
Cloth
Tubing
Cord
Lap
Tape
Tubing
TABLE
57. ASBESTOS
TEXTILE
GRADES10
£
Grade Asbestos content by weight
Commercial 75% up to but not including 80%
Underwriters' 80% up to but not including 85%
Grade A 85% up to but not including 90%
Grade AA 90% up to but not including 95%
Grade AAA 95% up to but not including 99%
Grade AAAA 99% up to and including 100%
aAsbestos textile grades differ with each asbestos tex-
tile form.
224
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Asbestos thread is produced in both plain (nonmetallic) and metallic
(wire inserted) classes (A and B), the latter being noted for its great
tensile strength and high thermal stability. Asbestos thread is generally
furnished in Underwriters' grade.
Asbestos cloth is woven from five classes of asbestos yarns. The most
widely used fabrics are woven from Class A (plain or nonmetallic) yarns and
Class B (metallic or wire inserted) yarns. Other fabrics are made from Class
C, D and E reinforced yarns. The different classes of asbestos cloth are
listed below:
• Class A—Cloth constructed of asbestos yarns containing no
reinforcing strands.
• Class B—Cloth constructed of asbestos yarns containing
wire reinforcing strands.
• Class C—Cloth constructed of asbestos yarns containing
organic reinforcing strands.
• Class D—Cloth constructed of asbestos yarns containing
nonmetallic inorganic reinforcing strands.
• Class E—Cloth constructed of two or more of the yarns
used in Classes A through D.
Asbestos cord is manufactured in all standard ASTM grades. The diameters
of asbestos cord range from 0.15 cm (0.06 in.) to 0.97 cm (0.38 in.). Asbestos
rope is available in commercial grade for most general uses and in Underwriters'
AA, AAA, and AAAA grades depending on service requirements. Tape is manufactured
mainly as plain or nonmetallic tape and as a wire inserted product; those used
in thermal insulation are manufactured in all of the standard ASTM grades.
Asbestos tubing also comes in all of these grades; roving is blended with cot-
ton or other organic fibers, producing various degrees of density to meet
specific requirements of the user. This is also applied in the five standard
ASTM grades. Asbestos lap comes in two styles: one is a single ribbon-like
formation of fibers and the other a paralleled assemblage of the first. It
comes in A, AA, and AAA grades. Felts come in all grades and are available
both with or without glass cloth reinforcement; they are produced in sheets,
tapes, and rolls. Wick is usually of commercial grade but other grades can be
supplied on order. In most cases the textiles are coated or bound with resins
or elastomers before being worked into a final product. They can also be
sprayed with a metal like aluminum to reflect heat. When braided to make pack-
ing and gaskets, the material may be impregnated with different compounds.
For example, graphite is commonly used to impart better frictional and binding
properties.
225
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Uses and Applications
About two-thirds of all manufactured asbestos textile material is an
intermediate product used in other industry categories such as friction ma-
terials, insulation, or gasketing. Long fibers are spun into yarn, cord,
thread, cloth, roving, rope, tape, braid, and corded fibers which may sub-
sequently be worked into protective clothing, insulation, filters, or dia-
phragms. The form the textile product takes is dependent upon its intended
end use as presented below:
• Lap - electrical insulation
• Roving - insulation for heater cords, twisted to form yarn
• Yarn - woven into textiles
• Cord - seals, packings, insulation
• Cloth - curtains, blankets, safety clothing
• Tubing - sleeving for electrical conductors
• Wick - packing and seals
• Tape - electrical insulation
Asbestos fire-resistant materials are used in a variety of applications,
including welding curtains, draperies, blankets, protective clothing, hot con-
veyor belts, furnace shields and molten metal splash protection aprons.10 In
addition, asbestos fire-resistant materials are used in the construction field
as temporary blankets or curtains. Further, they are used in the military,
fire-fighting and aerospace fields for protective clothing and in various rocket
and missile parts. Ironing board covers and theater curtains also contain these
materials.
Asbestos textiles are used as thermal insulation in pipe wraps for safety
protection; stress relieving pads in welding operations; protective coverings
for hot glassware utensils such as pincers and tongs; coverings for diesel
engine exhaust lines; flue sleeves; and braided walls in the construction of
steam hoses.11
Asbestos textiles are employed for the insulation of wires and cables,
especially those which are designed for low voltage, high-current use under
severe temperature conditions. They are also used for insulation of arcing
barriers in switches, circuit breakers, heater cords, and motor windings, and
as sleevings for electrical appliance leads and insulated conductors where fire
protection and resistance to mechanical abrasion are needed.
Asbestos textiles are used for pump packings; all purpose shaft and valve
stem packings' expansion joints; manhole gaskets; seals for boilers, ovens, and
furnaces; flange gaskets; and gaskets for storage tanks, cookers, and dryers.
226
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The applications of woven asbestos brake linings are mainly found in in-
dustrial band and drum brakes contained in cranes, lifts, excavators, winches,
concrete mixers and mine equipment. Woven asbestos may be used as clutch
facings for industrial band, plate and cone clutches in cranes, lifts, excava-
tors and winches. Automotive brake pads can use a woven asbestos cloth which
may be reinforced with brass wire or impregnated with phenolic resin, as is
commonly used in clutches.12
Asbestos carded fiber is the main form of asbestos textiles that can be
used in specialty products. Carded fiber is used mainly in liquid filters for
such products as beer, wine, oils and chemicals; and in electrolytic diaphragms.
It is also used as wiping pads for molten metal and as stuffing box packing.
Special Qualities
Asbestos withstands high temperatures more effectively than any of the
resins and organics with which it is bound. It remains unaffected by the
combination of moisture and heat. Although asbestos will suffer thermal
degradation and some loss of strength at elevated temperatures, fibers will
not burn, splinter or disintegrate when in contact with flame. Strength
retention for several grades of asbestos textiles at elevated temperatures
is shown in Figure 28. Pure chrysotile is stable in continuous use at tem-
peratures up to 480°C and can be used in higher temperature applications if
exposure is discontinuous.1 Asbestos fibers also restrict the thermal expan-
sion of materials with which they have been combined and impart a high resis-
tance to impact and abrasion to the final product.13
SUBSTITUTES
At a recently held conference concerned with the availability of sub-
stitutes for various asbestos products, a supplier of asbestos-free textiles
stated, "... it is very safe to say that there is a replacement for every
asbestos textile product right now."1^ Asbestos substitutes available for
fire resistant applications include: fiberglass, ceramics, organics, graphite,
carbon, quartz, cotton, and special wool blends. These products, when woven
into cloth, can be substituted for asbestos in a majority of cases, displaying
similar or even better properties. In general, replacement of asbestos must
be made on an application-by-application basis, taking into considerations such
factors as cost, performance, and service life. Table 58 presents the physical
and chemical properties of available substitute materials for textile products.
At service temperatures below 204°C (400°F) or at higher temperatures
with shorter exposure time, there appears to be little difficulty in select-
ing a suitable replacement. Even in high temperature applications above
204°C (400°F), there are a number of materials available that are designed to
replace asbestos.37 High temperature fiberglass, an alumino silicate (a
ceramic-type material), and an aluminum borosilicate material sold under the
name Zetex® all offer temperature resistance and fiber strength comparable to
or exceeding that of asbestos.16'38
227
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T- -j-
TEXTILE GRADE
ASBESTOS CONTENT BY WEIGHT
GRADE AAAA
99% UP TO AND INCLUDING 100%
GRADE AAA
95% UP TO BUT NOT INCLUDING 99%
GRADE AA
90% UP TO BUT NOT INCLUDING 95%
UNDERWRITERS GRADE
80% UP TO BUT NOT INCLUDING 85%
COMMERCIAL GRADE
75% UP TO BUT NOT INCLUDING 80%
600 F "3 100°/
. 800 F^100%
400° F 7/
6oo° f y/z///
- . —— /A
\y///AMo°*///A
• vay:-:-w.v 40 o °f
: 8 oo0 f
600°
800° F
4oo«*&ssa
NX 600°F
800° F
30 40 50 60 TO
PERCENT STRENGTH RETENTION
80
90
100
Figure 28. Strength retention of plain (nonmetallic) asbestos textiles after 24-hour exposure
to temperatures of 400°, 600°> and 800°F (190; 280; 380 C respectively).
-------
TABLE 58. ASBESTOS AND SUBSTITUTE MATERIAL PROPERTY COMPARISON FOR TEXTILE PRODUCTS
Material
(Manufacturer)
Properties
Product
application
Temperature Tensile
resistance3 strength**
up to °C (®F) kPa (psi)
Comments
References
Asbestos
Glass
TM
Zetex
(Newtex Industries, Inc.)
All applications requiring 649 5.68 x 10
an incombustible high (1200)c (824,000)
temperature fabric.
All applications requiring 538 2.17 x 106
an incombustible high (1000) (315,000)
temperature fabric.
Fire-resistant materials; 1538 3.44 x 106
thermal and electrical (2800) (500,000)
insulation; packings and
gaskets.
Low thermal conductivity; excellent radiation
stability; good flexibility; excellent resistance
to moisture and corrosion; excellent spinnability;
contains a minimim of magnetic or conductive fibers.
Density similar to asbestos; excellent handling
characteristics; high dielectric strength; not as
durable as asbestos; may produce some skin
irritation; fiber diameter 0.066 mm (0.0026 inch).
Excellent strength and durability; excellent
dielectric strength; dimensional stability; excellent
cutting, sewing and handling; abrasion-resistant;
fiber size -9 microns; lower (less than one-half)
thermal conductivity than asbestos.
6,11
15,16
ho
ho
vo
Ceramics
Nextel 312
(3M Company)
All applications requiring 1427
an incombustible high (2600)
temperature fabric.
Fire-resistant materials; 1427
thermal and electrical (2600)
insulation, packings and
gaskets.
high
1.72 x 106
(250,000)
A high tensile strength silica
flexible; abrasion-resistant
alumina fiber;
High strength retention; low shrinkage; abrasion-
resistant (after 4 hours at 816°C (1500°F), it retained
100 percent of its strength); good flexibility; some
skin irritation; fiber size 10 to 12 microns in
diameter.
17,18
Refrasil
(Hitco Materials)
Fire-resistant materials; 928
thermal and electrical (1800)
insulation; packings and
gaskets.
5.17 x 105
(75,000)
Good acid resistance; good dielectric properties;
excellent resistant to thermal shock; high capacity
to absorb moisture; lacks abrasion resistance,
fiber diameter 8 to 12 microns.
19,20
Organics
Nomex
(DuPont Co.)
Kevlar
(DuPont Co.)
Teflon
(DuPont Co.)
Fire-resistant materials;
thermal and electrical
insulation packings and
gaskets
Fire-resistant materials;
friction materials; cables.
Fire-resistant materials;
thermal and electrical
insulation; packings and
gaskets.
371
(700)
204
(400)
316
(600)
6.89 x 105 Abrasion-resistant; flexible; radiation-resistant;
(100,000) chemical-resistant; washable; low shrinkage.
2.76 x 10 High thermal stability; excellent chemical
(400,000) resistance; excellent cut resistance; low thermal
conductivity.
3.62 x 105 High chemical resistance; low friction and adhesion;
(52,500) low shrinkage; great flex-abrasion resistance;
radiation-resistant.
6,21,22
22,23
22,23
(continued)
-------
TABLE 58 (continued)
Properties
Material
(Manufacturer)
Product
application
Temperature Tensile^
resistance8 strength
up to °C (°F) kPa (psi)
Comments
References
K>
LP
O
Kynol™
(American Kynol, Inc.)
P. B.I.™
(Celanese Plastics and
Specialties Co.)
Fiberfrax
(Carborundum Co.)
Carbon
Celion
(Celanese Plastics and
Specialties Co.)
Celiox™
(Celanese Plastics and
Specialties Co.)
Fire-resistant materials;
packings and gaskets.
Fire-resistant materials.
Fire-resistant materials;
thermal and electrical
insulation; packings and
gaskets.
Fire-resistant materials;
packings and gaskets;
friction materials.
Friction materials;
packings and gaskets.
Fire-resistant materials.
704 ,
(1300)
500
(932)
1260
(2300)
1427
(2600)
5432
(3000)
(no oxygen)
760
(1400)
1.86 x 10*
(27,000)
2.07 x 106
(300,000)
1.72 x 106
(250,000)
Low moisture absorption; acid-resistant; low toxic
off gases; low shrinkage; is a carbon precursor;
low abrasion.
Polybenzimidazole; nonflammable in air; little or no
emittance of toxic off gases; acid-resistant;
readily processed on conventional textile equipment;
comfortable; good cryogenic characteristics; high
moisture regain.
Chemical-resistant; low thermal conductivity;
resists oxidation and reduction; excellent resist-
ance to thermal shock.
Over High flexibility, lightweight, good retention of
3.10 x 106 fiber properties at high temperatures.
(450,000)
3.24 x 106 Flexible, low shrinkage; excellent oxidative
(470,000) stability; excellent adhesion to organics;
excellent electrical/thermal conductivity.
2.10 x 105 Lightweight, flexible, high moisture regain, low
(30,500) density, readily converted into carbon
15,24,25
26,27
28,29
6,30,31
30,31
30,32
Quartz
Alphaquartz
(Alpha Associates)
Cotton
(Westex, Inc.)
Fire-resistant materials;
thermal and electrical
insulation; packings and
gaskets.
Fire-resistant materials.
Over
1204
(2200)
232
(450)
8.69 x 10s
(126,000)
8.62 x 10s
(125,000)
temperatures depend upon product application.
^Figures are for fibers only, and are not necessarily related to fabric strength.
°Wire inserted asbestos textiles.
^Carbonizing temperature range.
Thermal stability; elastic; excellent resistance 33,34,35
to thermal shock; easily impregnated; excellent
abrasive characteristics; high purity; transparency
to electromagnetic and radio waves.
Flame-resistant; is coated and treated; washable; 11,36
fiber diameter 0.020 to 0.030 mm (0.0008 to
0.0011 inches).
-------
In addition to providing high heat resistance and fiber strength, these
asbestos replacement products offer insulating properties comparable to those
of asbestos. A fourth asbestos replacement material, an aromatic polyamide
cloth, is widely used in the manufacture of protective clot.hing, fire blankets,
etc. Inorganic asbestos replacements also offer good chemical resistance and
resist most attacks from most corrosive agents, with the exception of HF and
phosphoric acids and strong alkalies. The aromatic polyamide is resistant to
most commonly used solvents.
The competitive ability of a nonasbestos textile material is dependent
upon economic considerations as well as technical factors. Substitution is
limited to some extent by cost barriers, since only glass fibers are less
expensive than asbestos fibers. However, when considering costs, the product
life must also be considered because there are some occasions where the sub-
stitute products are more applicable for a particular job than an asbestos
product—this may result in longer product life, and therefore lower overall
costs.
MANUFACTURING
Primary Manufacture
Textile plants may produce more than a dozen different products.
Thousands of operations may occur simultaneously as fibers are wound into
strands, rewound, spun, twisted, braided, and woven providing numerous
sources of fiber dust.
Two basic variations are used in asbestos textile manufacturing: the
conventional process and the wet process. Most textiles are made with the
conventional process, using either the dry or damp method. The dry and damp
methods are identical except that during the damp process the yarn is mois-
tened either by contact with water on a roller or by a mist spray to reduce
fiber emissions. Conventional dry process manufacturing produces a small
volume of highly specialized yarn without absorbing any water. The newly
developed wet process yields a dense yarn by extruding a chemically dispersed
slurry into a chemical coagulant. The product tends to hold asbestos fibers
better than those produced by the conventional processes, reducing workplace
fiber levels but the yarn formed has the disadvantages of poor absorption and
impregnation characteristics.1
Raw asbestos fibers of various grades are mixed to obtain desired charac-
teristics in the final product. The different asbestos grades received in
bags from suppliers are weighed, then manually opened and dumped into blenders
with several other raw materials.
The basic steps for the production of asbestos textile material are shown
in Figure 29. Asbestos fiber is typically transported in a dry state by rail-
car or truck and is contained in palletized paper or plastic bags. A recent
trend has been towards employing shrunk-wrapped pallets which is now a cus-
tomer option. At the plant, this material is unloaded either manually or by
231
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SAGGED ASBESTOS FIBER
AS RECEIVED FROM MILL
Flowsheet of a Typical
AsbuBtos Textile
Plant
FIBER PREPARATION
BLENDING
CARDED
RAYON. COTTON
ROVING
TWISTING
LIGHT
GAUGE
WICKAVv
SPINNING
METALLIC
YARNS
TWISTING
TWISTING
PLIED j~-
YARNSRr
TWISTED
ROPE
THREAD
BRAIDING
BRAIDING
WEAVING
CLOTH WOVEN BRAIDED BRAIDED BRAIDE
TU91NG TUBING CORD ROPE
TAPE
Figure 29. Manufacturing operations for asbestos textiles.1
232
-------
powered fork-lift trucks and transported to a raw-fiber warehouse for inter-
mediate storage. At most facilities housekeeping practices such as tapping
broken bags and vacuuming the trucks or railcars prior to unloading are
employed.
Raw asbestos fibers of various grades are mixed to obtain desired charac-
teristics in the final product. The different asbestos grades received in bags
from suppliers are weighed, then manually opened and dumped into blenders with
several other raw materials. The asbestos fibers are often blended with a small
portion (10 to 15 percent) of cotton or rayon stable to aid in the processing.
The blenders continually mix the ingredients which slowly move to the rear of
the machine, go up an incline and drop to the bottom while some of the mix
falls into a hopper. The rear of the blender is enclosed and hooded to prevent
fiber release. Once the hoppers are filled with blended material they are
transferred to the carding operation.1
A carding machine combs the fiber mix into a paralleled fiber mat which
is mechanically pressed and layered into a lap. At the finishing card, the
lap is separated into thin, continuous fiber strips called roving. Cotton,
rayon, or some other material may be added at this stage to impart strength
or other characteristics. Lap, matting, or roving may be sold to a secondary
processor; otherwise, the roving proceeds to spinning frames.
The roving is twisted or spun to a specified number of turns per inch to
impart strength. In the damp process, the roving is wet before spinning to
reduce asbestos dust but in some cases to retain product quality, the product
is not wet.
During spinning and further processing many strands break. The whipping
ends flying around spindles must be repaired manually, requiring workers to
spend time in a dusty environment.
Spun roving, known as single yarn, may be twisted with other single yarns,
wire, or other material to produce plied yarn which can be coated to produce
thread or treated yarns. Otherwise, the plied yarn may be woven to produce
tapes, cloth or woven tubing, or braided to produce cord, rope, or braided
tubing. Spun yarn may also omit twisting and be used directly in woven,
braided, or treated products. Asbestos yarn may then be processed at weaving
looms, and placed on beams or cruels which feed the loom a large number of
strands. Either damp or dry looms may be used.1
The wet process differs from the others in that raw asbestos is dumped
directly into a slurry tank with water and chemicals. The slurry is extruded
into strands that are then spun or otherwise processed similar to other fibers.
The wet process completely avoids blending and carding, thus eliminating some
sources of asbestos dust. Since wet-processed textiles have characteristics
that differ from dry-processed textiles, manufacturers use different production
techniques to compensate for altered process ability.
233
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Secondary Manufacture
Primary asbestos textile products are fabricated into consumer end prod-
ucts by secondary processors and distributors. They may cut, sew, impregnate,
recoat, mold, prime, and reform the primary products.
Manufacturing Plants
Presently, only three firms are known to be producing primary asbestos
textile products. They are listed in Table 59.
TABLE 59. MANUFACTURERS OF ASBESTOS TEXTILES1
Company Location
Raybestos - Manhattan Inc. North Charleston, NC
Marshville, NC
Southern Textiles Corp.3 Charlotte, NC
Amatex Corporation Meredith, NH
Norristown, PA
aA subsidiary of H. K. Porter Co., Inc., Pittsburgh, PA.
Production Volumes
As stated previously, an estimated 1,900 metric tons of chrysotile asbes-
tos were used to manufacture textile products in 1980.2 The majority of this
total was grade 3 chrysotile. Asbestos used in electrical insulation materials,
a subcategory identified separately from textiles by the Bureau of Mines,
amounted to 2,900 metric tons in 1980.2 This asbestos was used mainly in the
forms of paper, roving, webbing, and braid where comparatively high tempera-
tures may occur. Production volumes for individual asbestos textiles manufac-
tured are not available.
ASBESTOS RELEASE
Input/Output
Figure 30 shows estimated process disposal and emissions for the asbestos
textile industry based on Levine's40 1974 estimates projected to 1980 U.S.
Bureau of Mines consumption figures. Of the 1,900 metric tons entering the
process as raw asbestos fiber, approximately 1,851.9 metric tons are contained
in the final product and 48 metric tons are sent to disposal as vacuum cleaner
and baghouse dust and product scraps. An estimated 0.3 metric tons escape
through a control device (typically a baghouse). Levine's atmospheric emis-
sion estimates are based on gross assumptions with a reported uncertainty of
at least an order of magnitude. Meylan reports emissions of 1 to 3 orders
of magnitude less. Atmospheric emissions from disposal based on GCA estimates,
are shown to be 0.1 metric tons. This estimate is loosely based on Levine's
234
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MANUFACTURING OPERATIONS
RAW
ASBESTOS
FIBERS
RECEIVING
AND
STORAGE
CARDING
AND
COMBING
BRAIDING
OR
WEAVING
PNEUMATIC
GRADING
MATTING
SPINNING
CONSUMER
,900 TPY
1,852 TPY
VACUUMED
DUST
LEGEND
BAGHOUSE
C INPUT/OUTPUT
I 1 MANUFACTURING
I I PROCESSES
CONTROL EQUIPMENT
\ BAGHOUSE
'•.EMISSIONS
BAGHOUSE
CATCH
ULTIMATE DEPOSITION
SOLID
WATER
SOLID
WASTE
DISPOSAL
AIR
EMISSIONS
WATER
EMISSIONS
DISPOSAL
EMISSIONS
0.1 TPY
1(8 TPY OA TPY 0-7 TPY
Figure 30. Process and disposal emissions (in metric tons/year) for asbestos textiles.15
-------
data, and takes into account the Asbestos NESHAP's regulations amended in
1975 regarding the disposal of asbestos. An estimated 0.7 metric tons of
asbestos are discharged in process wastewater.
During Manufacture
Workplace Exposure—
High fiber counts, relative to other asbestos processing industries, have
been traditionally encountered throughout the asbestos textile industry. Dry
processing plants have a potential to generate severe exposure problems since
no phase of the process uses wetting to reduce dust. Table 60 shows the time-
weighted exposure levels at different points in the textile production pro-
cess.7 As shown in this table, worker exposure levels can approach 15 fibers/
cc. These high fiber levels can be substantially reduced by employing effec-
tive control measures such as well-designed ventilating equipment. Raybestos-
Manhattan, a major manufacturer of asbestos textiles, implemented an extensive
dust control plan (from 1975 through 1977) which dramatically decreased high
fiber levels to below 1 fiber/cc.41 This dust control plan, described below,
exemplifies fiber control options available to the asbestos textile industry.
TABLE 60. TIME-WEIGHTED AVERAGE FIBER C0UNTSa - ASBESTOS TEXTILES7
Fiber Count
(fibers/cc)
Process step
Typical
Damp
Dry
Wet
Receiving and storage
1.0
0.25-2.5
0.25-2.5
0.25-2.5
Fiber introduction
4.0
2.0-10.00
2.0-10.00
2.0-8.0
Mixing and blending
4.0
N/A
2.0-10.00
N/A
Carding
4.0
N/A
2.0-10.00
N/A
Spinning
4.0
2.0-10.00
2.0-15.00
2.0
Twisting
4.0
4.0-10.00
N.A.
2.0
Weaving
3.0
1.0-4.0
N.A.
1.0
Braiding
3.0
2.0-5.0
N.A.
1.0
aNI0SH fibers 5 pm or longer counted using optical microscopy.
N/A = Not applicable
N.A. = Data not available
Based on plants representing 96 percent of asbestos textile
production.
236
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The Raybestos-Manhattan Marshville plant, prior to implementation of the
Dust Control Plan, was an antiquated plant with high fiber levels associated
with most of the processes. To reduce dust levels, which were barely below
12 f/cc, the following strategies were developed:
• Eliminate all manual handling of raw asbestos fiber by use of a
closed system where possible.
• Reduce dust generation by effective exhausting or wetting where
possible.
• Upgrade and expand existing building, simplify vacuum cleaning
by having smooth walls and avoid ledges and surfaces that
catch and retain dust.
• By design, provide for a safe, clean method of waste collec-
tion and reuse and/or removal.
Greatly improved particulate capture and dust control was achieved by
the installation of extensive engineering controls that included a baghouse,
enclosed hooding, and a well-designed ventilation network. Raybestos-Manhattan
also adopted specific work practices and administrative procedures. The work
practices established focused on improved maintenance, waste handling, bag-
house operating, and housekeeping procedures. Administrative action included
requiring protective equipment be worn, enforcing disciplining actions, assign-
ing clean-up personnel to complement engineering controls, establishing em-
ployee education programs and instituting a dust monitoring program. The
action plan to implement the dust control strategy required 2 years for com-
pletion after which fiber counts were reduced to less than 1 f/cc and at the same
time increased the plant capacity considerably.41
Emissions to Air
Asbestos fiber release to the ambient air results principally from control
equipment air exhaust. Since baghouses are almost universally employed to con-
trol fiber emissions, collection efficiencies are relatively high (99.9 percent).
Providing the baghouses are well maintained and malfunctions and spills are
minimized, emissions from control equipment exhaust is expected to be low.
A manufacturer of commercial grade asbestos textiles using the dry process,
recently reported that much of the asbestos entering the process does not leave
in final products.41 For products containing 75 to 80 percent asbestos, it was
estimated that about 10 to 15 percent of the input is lost in carding, 2 to 3
percent lost in twisting and an additional 2 to 3 percent lost in cording.
This results in an average total manufacturing loss of 17.5 percent. By provid-
ing proper aspiration to control equipment, facilities are able to capture most
of the loss in baghouses and recycle it. However, at a facility producing
asbestos products other than textiles alone, the fiber is sent to other produc-
tion units. It was found that relatively short fibers were released during
textile manufacturing and if collected and recycled into the same process only
237
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wound up being released again. By sending the short fibers released from the
textile process into a process like papermaking, where all fibers are short,
overall emissions are reduced.
Assuming 0.0175 percent of the asbestos entering the processes is emitted
to the ambient air through control equipment, (99.9 percent control) total fiber
emissions to the ambient air from all asbestos textile manufacturing is calculated
to be 0.03 metric tons, based on 1980 production figures. This estimation is
very rough and requires verification by actual sampling of baghouse exhaust.
Fiber emissions to the ambient air from wet processing are considered to
be minimal. Because of the high moisture content of the strands formed, wet
processing completely eliminates dust generated in blending and carding since
these steps are eliminated. Fiber is introduced directly into a slurry and
underwater extrusion is used to produce strands. The amount of asbestos
emitted to the atmosphere from textile operations is estimated to be less
than 0.1 ton per year.
Actual measurements of the asbestos fiber concentration in the vicinity
of an asbestos textile plant are very limited. However, Suta and Levine"*2
estimated concentrations near industrial facilities using mathematically de-
rived dispersion curves of assumed plant emissions. In the case of asbestos
textiles, it was estimated that a population within 5 km of a manufacturing
plant would be exposed to a median atmospheric asbestos concentration of
21.0 and 1.3 ng/m for urban and rural facilities, respectively. Comparing
this data with the median U.S. atmospheric asbestos fiber concentration
(20 ng/m3), it appears that asbestos textile manufacturing contributes little
to nonoccupational exposure. However, actual ambient monitoring in the
vicinity of an asbestos textile facility is necessary to confirm Suta and
Levine's estimates.
Release to Land—
Solid waste from asbestos textiles arises from scraps produced in manu-
facture and from dust collected in baghouses treating vented air. Some
scraps can be recycled to fabrication, but the total solid waste produced in
cutting, trimming, and sizing may range from 1 to 2 percent or from 50 to 100
tons per year.6 This agrees with estimates by Levine1*0 of 48 metric tons
when Levine's 1974 estimates are projected to 1980 U.S. Bureau of Mines2
consumption figures.
Release to Water—
Dry textile production processes have no significant wastewater effluent
streams. A small amount of water is generally used to wet yarns to reduce
dust in the weaving process. However, the amount of water used is minimal
and is evaporated.
Even in the wet process the amount of water to be disposed of is small
and is generally discharged to city sewers. Projecting Levine's40 estimates
to 1980 consumption figures, it is estimated that 0.7 metric tons is lost to
the water. GCA estimates that this figure represents a high end since it very
likely includes asbestos captured by wet scrubbers used to control dust emis-
sions. Wet scrubbers have typically been replaced with baghouses.
238
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During Use
Textile products may be cut, torn, stitched, or stapled during instal-
lation or use. Measurements of ambient fiber levels have been made aboard
ship in a British shipyard during application and stitching asbestos cloth.
Measured values ranged from 0.05 to 0.26 fibers per cc.1*3 A later study
conducted by the same researcher revealed fiber counts of up to 43 fibers
per cc while tearing and applying untreated cloth.1''1 In the same study,
tearing of asbestos-containing cloth produced fiber counts of less than 0.1
fibers per cc.1*4 These study results, however, are somewhat suspect since
the cloth was being applied over molded asbestos insulation. It is certain
that some fibers emitted from the insulation contributed to the fiber count,
but there is no way to estimate the extent of this contribution.1*5
One asbestos textile manufacturer reported low ambient fiber levels,
0.01 to 0.05 fibers per cc, during cutting of untreated lagging cloth and
lower counts, 0.0 to 0.04 fibers per cc during application. 5 Almost all
asbestos textiles produced in the United States are coated or impregnated
to inhibit fiber release. On the basis of these data it seems reasonable
to estimate that the use of asbestos textiles will not produce exposure
levels above 0.01 fibers per cc.1*5
During Disposal
Textile products generally have short life applications, and are dis-
posed of as worn out scrap in waste dumps. Nearly all textile materials are
coated or impregnated to suppress dust, so release to the environment should
be minor. It has been estimated that about 7,400 m.t. per year are scrapped
and sent to landfills or other waste dumps.1 The amount disposed of annually
may be higher than the amount being produced simply due to the backlog of
asbestos produced earlier and still in use. With time, disposal volumes will
stabilize near the current production level.
CONCLUSION
The Bureau of Mines has projected a zero demand for asbestos in textiles
by the year 2000.2 This projection is based in part on the fact that there
are a number of viable substitutes for asbestos textile materials that are
well suited to replace asbestos in nearly every application. These include:
Fiberglass, Kevlar, Nomex, Teflon, Refrasil, Siltemp, Norfab, Durette, Nextel,
Kynol, Celiox, Celion, Zetex, and Fiberfrax. In addition, other products
are still in developmental stages. Many of these substitutes have better
property advantages for textile applications than asbestos. Although more
costly in most cases, these alternatives are already on the marketplace,
providing a nonasbestos choice for consumers. As in the other categories
mentioned, where viable substitutes exist, the choice of substitutes involves
consumer education and acceptance of a changeover from the established
product. As there are some occasions where the substitute products are more
239
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applicable for a particular job, their use may result in longer product life,
leading to lower overall cost and public acceptance. The small number of
asbestos textile applications for which no satisfactory alternative exists at
present includes lamp and stove wicks, wipes for molten metal, diaphragms for
some of the electrolytic cells and some filter cloths.10
In the future, the market for nonasbestos, fire-resistant materials will
undoubtedly improve. The performance of high temperature application sub-
stitute materials such as fiberglass and ceramics has proven that these ma-
terials not only compare with, but often exceed the performance characteristics
of asbestos. With the substitute materials currently on the market, and
assuming new developments of asbestos replacement products in the future, as-
bestos consumption in fire-resistant materials will drop significantly. Sales
of asbestos insulation products have already shown this drop in their drastic
decrease in sales over the past few years.
In summary, it is anticipated that the consumption of asbestos in tex-
tiles will continue to decline as only those applications where asbestos can-
not be replaced economically continue to use asbestos.
240
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references
1. Meylan, W. M. , et al. Chemical Market Input/Output Analysis of Selected
Chemical Substances to Assess Sources of Environmental Contamination:
Task III - Asbestos. EPA-560/6-78-005. August 1978.
2. Clifton, R. A. Asbestos. 1980 Mineral Yearbook. U.S. Bureau of Mines,
Washington, D.C.
3. Clifton, R. A. Asbestos. 1978-1979 Mineral Yearbook. U.S. Bureau of
Mines, Washington, D.C.
4. Davis, W. E. and Associates. National Inventory of Sources and Emissions:
Asbestos - 1968. U.S. Environmental Protection Agency. February 1970.
5. Arthur D. Little, Inc. Impact of Proposed OSHA Standard for Asbestos -
First Report to the United States Department of Labor. OSHA. April 28,
1972.
6. Sores, Inc. and Arthur D. Little, Inc. Characterization of the U.S.
Textile Markets. Ministere De L?Industrie Et Du Commerce, Government du
Quebec. Final Draft Report. May 1976.
7. 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.
8. Gregg, R. T. Development Document of Effluent Limitations Guidelines
and New Source Performance Standards for the Textile, Friction Materials
and Sealing Devices Segment of the Asbestos Manufacturing Point Source
Category. U.S. National Technical Information Service, PB-240-860.
December 1974.
9. Sullivan, R. J., and Athanassindis, Yanis. Preliminary Air Pollution
Survey of Asbestos, A Literature Review, U.S. Department of Health,
Education, and Welfare. October 1969.
10, Handbook of Asbestos Textiles. American Textile Institute. 3rd Edition.
1967.
11. Clifton, R. A. Asbestos 1978. U.S. Department of the Interior, Bureau
of Mines, Washington, D.C. August 1979.
241
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12,
13,
14
15
16
17
18
19
20
21
22
23
24
25
26
Michaels, L. , and S. S. Chissizk, ed. Asbestos: Properties, Applica-
tions, and Hazards. Volume 1. John Wiley and Sons, 1979, pp. 305-367.
Bradfield, R. E. N. Asbestos: Review of Uses, Health Effects, Measure-
ment and Control. Atkins Research and Development, Epsom Surrey,
England. January 1977.
Manfer, S. G. The Carborundum Co., Niagara Falls, N.Y. Speech given
at U.S. EPA/CPSC "Substitutes to Asbestos" Conference, Arlington, Va.
July 14-16, 1980.
Telecon. Dixit, B., President, Newtex Industries, Inc., Victor, N.Y.,
(716) 924-9135, with T. Henderson, GCA/Technology Division, January 30,
1980. Notebook No. 07, Phone call No. 11.
Newtex Industries Inc. Zetex^M Bulletin. Victor, N.Y. 1979.
Telecon. Ellingson, L. Sales Representative, Ceramic Fiber Products/
3M Company, St. Paul. Minn. (612) 733-1558, with T. Henderson, GCA/
Technology Division, January 31, 1980. Notebook No. 07, Phone call
No. 18.
Ceramic Fiber Products, 3M Company. Nextel® 312 Ceramic Fiber Products.
N-MTDS (79.5) MP. and N-MPBBS-(89.5) 11. St. Paul, Minn.
Telecon. Black, M., Sales Representative, Hitco Materials Division,
Gardena, Calif., (213) 321-8080, with T. Henderson, GCA/Technology
Division, January 30, 1980, Notebook No. 07, Phone call No. 11.
Hitco Materials Div. Refrasil Product Data Bulletins. P.O. LHT/MD-1779
15 M CP and LHT/MD-275 6M CP. Gardena, Calif. November 1979. p. 1-2.
E. I. DuPont de Nemours & Co., Inc. DuPont Technical Information Bulletin.
N-236. Wilmington, Del. October 1969. p. 1-12.
Telecon. Chiostergi, R. Marketing Manager, E. I. DuPont de Nemours & Co.,
Inc. Wilmington, Del., (302) 999-3951, with T. Henderson, GCA/Technology
Division, February 1, 1980. Notebook No. 07, Phone call No. 20.
E. I. DuPont Nemours & Co., Inc. Characteristics and Uses of Kevlar®
29 Aramid. N-375. Wilmington, Del. September 1976. p. 1-7.
American Kynol, Inc. Kynol^ novoloid Bulletin. A-10, 003. New York,
N.Y. October 1974. p. 1-11.
Telecon. Storti, M., Marketing Manager, American Kynol Inc., New York,
N.Y., (212) 279-2858, with T. Henderson, GCA/Technology Division.
February 1, 1980. Notebook No. 07, Phone call No. 23.
Celanese Corp. PBI™, Polybenzimidazole Fiber. Charlotte, N.C.
February 1979. p. 2.
242
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27. Telecon. McCallister, K. C., Marketing Manager, Celanese Corporation,
Charlotte, N.C., (704) 554-2000, with T. Henderson, GCA/Technology
Division, February 1, 1980. Notebook No. 07, Phone call No. 22.
28. Telecon. Pietak, K., Textile Specialist, The Carborundum Company, Niagara
Falls, N.Y. (716) 278-2000, with T. Henderson, GCA/Technology Division.
January 30, 1980, Notebook No. 07, Phone call No. 08.
29. The Carborundum Company. Fiberfrax® Product Bulletins. C736-A-G.
Niagara Falls, N.Y. p. 1-10.
30. Telecon. Timmons, B., Marketing Supervisor, Celanese Plastics and Special-
ties, Chatham, N.J., (201) 635-2600, with T. Henderson, GCA/Technology
Division, January 28, 1980. Notebook No. 07, Phone call No. 05.
31. Celanese Plastics and Specialties Co. Celion® Carbon Filters Bulletins.
Chatham, N.J. November 1979.
TM
32. Celanese Plastics and Specialties Co. Celiox Fibers Bulletin. Chatham,
N.J. November 1979.
33. Telecon. Saffadi, R., President, Alpha Associates, Woodbridge, N.J.,
(201) 634-5700, with T. Henderson, GCA/Technology Division, January 31,
1980. Notebook No. 07, Phone call No. 11.
34. Alpha Associates Inc. Alpha Quartz® Bulletins. Data Sheet Nos. 11690-
11693. Woodbridge, N.J. May 1979.
35. Lubin, G. High Silica and Quartz. In: Handbook of Fiberglass and
Advanced Plastics Composites. Reinhold Book Corporation. 1969.
p. 191-200.
36. Telecon. Wilander, R., Sales Manager, Westex Inc., Chicago, 111.,
(312) 523-6351, with T. Henderson, GCA/Technology Division, January 30,
1980. Notebook No. 07, Phone call No. 10.
37. Pye, A. M. A Review of Asbestos Substitute Materials in Industrial Appli-
cations. Journal of Hazardous Materials. 3:125-147. 1979.
38. Garlock Inc., Thermo-Ceram^. LX7/79-llm. Palmyra, N.Y.
39. Margolin, S. V. , and B. U. M. Igeve. Economic Analysis of Effluent
Guidelines: The Textile, Friction and Sealing Materials Segment of the
Asbestos Manufacturing Industry. U.S. National Tech. Inform. Service,
PB-250-682. 1975.
40. Levine, R., ed. Asbestos. An Information Resource. May 1978.
41. Lewinsohn, H. C., et al. Dust Control in a Conventional Asbestos Textile
Factory, Annal. New York Academy of Sciences, 1979.
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42. Suta, B. E., and R. J. Levine. Nonoccupational Asbestos Emissions and
Exposures. Asbestos-Properties, Applications and Hazards. Volume 1.
John Wiley and Sons, New York, N.Y. 1979.
43. Harries, P. G. Asbestos Hazards in Naval Dockyards. Annals of Occu-
pational Hygiene. Vol. 11, pp. 135-145. 1968.
44. Harries, P. G. Asbestos Dust Concentrations in Ship Repairing: A
Practical Approach to Improving Asbestos Hygiene in Naval Dockyards.
Annals of Occupational Hygiene, Vol. 14, pp. 241-254. 1974.
45. Wright, M. D., et al. Asbestos Dust Technological Feasibility Assessment
and Economic Impact Analysis of the Proposed Federal Occupational
Standard: Part I. U.S. Department of Labor. OSHA. September 1978.
(Draft) .
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SECTION 13
MISCELLANEOUS ASBESTOS USES
INTRODUCTION
In this section, the various users of asbestos fibers that do not fit
into the other nine industry segments defined by the EPA are discussed. These
miscellaneous products which have been used in the past or currently use asbes-
tos are:
• drilling muds
• shot gun shell base wads
• asphalt/asbestos cement
• foundry sands
• sprayed on insulation
• artificial snows
Of the above products, only drilling muds currently contain asbestos.
The other products, affected by Consumer Product Safety Commission bans or
OSHA and EPA regulatory programs, have completely discontinued asbestos use.
By discontinuing asbestos use in all but drilling muds, the total asbestos
fiber consumption of this miscellaneous class has been substantially reduced
from its 1976 usage rate of SS.OOO1 metric tons to a 1980 usage rate of 10,400
metric tons.2 Miscellaneous use of asbestos in 1980 accounted for 2.9 percent
of total asbestos use.
DRILLING MUDS
Product Summary
Drilling muds, also called drilling fluids, are used when wells are
drilled by the rotary method. This method involves a drill bit which is
turned by a drill pipe extending down to the bit from the surface of the
ground. The machinery for rotating the pipe is located at the ground surface.
The drilling mud is pumped down through the drill pipe and the drill bit and
then returns through the annulus between the drill pipe and the well bore
hole. 3 A'j the fast-moving drilling mud passes through the bit and back up to
the annulus, it cools and lubricates the bit and picks up the drilled cuttings,
carrying them to the surface. The bottom of the hole is thus left clean for
the drill bit. At the surface, the drilling mud passes through screening
245
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equipment which removes the chips of rocks ground away by the drill bit.
The mud is replenished with new additives and is recirculated through
the drill pipe to the drill bit. The process is repeated until the desired
depth is attained.4
Drilling muds typically contain anywhere from three to twelve different
additives out of over 150 minerals and chemicals which are appropriate for
drilling mud applications. When drilling begins, mud additives are dumped
into a hopper where they are blended with water. The mixture then goes to a
tank near the well and is pumped from this tank through the drilling system.4
Asbestos is used in drilling muds to increase the carrying capacity of
the mud (the ability of the mud to bring up cuttings) without significantly
increasing the mud viscosity. This is a useful property since it is easier
to pump a less viscous fluid which results in more power available at the
bit and a faster drilling rate. Additionally, asbestos acts as a loss-
circulation material; that is a material added to drilling mud to plug all
passages, cracks, and cavities in the drill hole to prevent the loss of the
drilling mud.5 Asbestos has the dual ability of increasing the carrying
capacity of drilling muds while at the same time acting as a loss-circulation
material at relatively low costs.
In the field, asbestos is added to the drilling fluids through a mud
hopper or large funnel. Asbestos is used in concentrations normally ranging
from 2 to 5 pounds per barrel [ 1 barrel = 159 liters (42 gallons) ] of mud.6
However, values as low as 0.5 pounds per barrel and as high as 20 pounds per
barrel have also been reported depending upon the desired characteristics of
the drilling mud. Initially, a volume of drilling mud ranging from 150-200
barrels is prepared and as drilling progresses, more drilling mud is prepared.
Under typical conditions, the drilling mud is prepared once every eight-hour
shift. The amount of asbestos added each time is normally less than 230 kilo-
grams (500 pounds).6
The choice of whether or not to use asbestos in a drilling mud is a func-
tion of the individual well site and depends upon the specific job, soil
characteristics, materials being drilled for, and cost effectiveness.
Substitutes
Asbestos serves a dual function in drilling muds. It increases the
carrying capacity (acting as a viscosifier) and also acts as a loss-circulation
material. No single substitute, except perhaps bentonite or attapulgite clays,
serve both functions, but a variety of substitutes can be used as viscosifiers
and a large number of additional materials can be used as loss-circulation
materials at a competitive cost to asbestos. These materials are both added
to the drilling mud to serve the functions that asbestos would perform.
Loss-circulation material substitutes can be used to obtain similar results
to that seen with asbestos fiber. With viscosifiers, each substitute product
may have a specific application and must be chosen according to the requirements
at the drilling site. Asbestos has a universal application as a viscosifier,
whereas substitute viscosifiers must be chosen for the specific application.
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The temperature of circulating drilling mud in oil wells is normally 52°C
to 60°C with a maximum temperature at the bottom of the hole of 149°C and some-
times as high as 204°C. Asbestos can be used at temperatures over 316°C before
it breaks down.7 Polymers can generally be used at temperatures of up to 148°C,
although new copolymers have been demonstrated at temperatures of 260°C to over
Syrc.* The bentonite, attapulgite, and other clays cannot withstand temper-
atures as high as asbestos, but can normally be used in most drilling appli-
cations from up to 177°C to 204°C. Bentonite is the most widely used viscosifier
for fresh water drilling systems and attapulgite is the most common viscosifier
for salt water drilling systems.0
Asbestos performance degrades readily from mechanical shear forces.
Xanthan gum polymer can be subjected to high mechanical shear without degrada-
tion.9 Clays, such as attapulgite, have the advantage of actually increasing
viscosity at higher shear forces.10
Manufacturing Summary
Manufacturing Process—
One manufacturer of asbestos used in drilling muds (Johns-Manville) pro-
cesses the asbestos in the following manner. The asbestos is extruded, highly
moisturized (12-15 percent) and then pelletized, thus binding the fibers
together. The manufacturer claims that this process produces an asbestos
product with negligible fiber release when it is used to make drilling muds.11
Name and Number of Manufacturers—
The asbestos product described above is sold under the tradename of
FLOSAL® and marketed by Drilling Specialties in Bartlesville, OK.12 Approx-
imately 1.6 million kilograms (3.5 million pounds) per year of FLOSAL are
made and marketed in the United States. The other American manufacturer of
an asbestos product for use in drilling muds is Union Carbide Corporation.
This product is marketed by Montello Company of Tulsa, OK under the tradename
Super Visbestos® and is advertized as being sheared, wet-refined, pelletized,
chrysotile asbestos.13 Information about annual product rates was given for
Super Visbestos, but upon further consideration, the Montello Company con-
sidered this information to be proprietary and it is not listed in this report.
The Johns-Manville Company mines their asbestos in Canada and the asbestos
used by Union Carbide is mined in California.11
Production Volumes—
Approximately 9900 metric tons (10,000 tons) of asbestos fiber were used
in drilling fluids in 1978. 11+>15 Current production is estimated to be 4900
metric tons (5000 tons) annually.6 The shorter grades of chrysotile fiber
are normally used in either pelletized or loose fiber form.15 Because the
two American manufacturers both produce a pelletized form of asbestos for
drilling muds, the loose fiber form is assumed to come from non-American
manufacturers.
247
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ASBESTOS RELEASE
Input/Output
During Manufacture
Workplace Exposure—
Worker exposure data, specific to the manufacture of pelletized asbestos
for use in drilling muds, is not available. The generation of free fibers from
shipping, receiving, pouring and mixing is likely to be in the same concentration
range as similar operations in the previously discussed nine product categories.
Fiber release from extruding and pelletizing are expected to be minimal since
the product is highly moisturized (12 to 15 percent).17
At drilling site, typically an amount of asbestos less than 500
pounds is introduced for mud production once every 8 hours during drilling.
The drilling workers are exposed to free fibers when bags of asbestos are
opened, emptied, and handled for disposal. The fiber counts are dependent
on many factors including the fiber form (pellets or loose) and atmospheric
conditions. Daly et al.,16 have reported the time-weighted average fiber
count at the mud pit as 0.4 fibers/cc with a maximum ceiling level of 1.9
fibers/cc. The low level is probably achieved when pelletized asbestos is
used.
Release to Land—
When drilling operations have been completed, the mud is usually dumped
or left in the mud pit and covered with dirt. The asbestos is encased and,
therefore, free fibers would not be expected. It is not known how empty
raw asbestos containers such as bags are discarded. More than likely they are
disposed of with other trash in a conventional manner.
Release to Water—
Asbestos fibers are very likely leached out of disposed drilling muds
which are usually dumped or left in the mud pit. Since there has been no
actual monitoring to determine the asbestos concentration in the leachate
from a drilling operation, it is not possible to quantify releases to water.
In addition, the fiber release rate would depend heavily on the drainage
characteristics of the dump site or mud pit.
During Use
The frequent moving from site to site makes fixed air pollution control
equipment unfeasible. Therefore, when asbestos is added to the drilling mud,
an undetermined quantity of fibers become airborne, dependent upon weather
conditions and the form of asbestos used (pelletized asbestos creates less
emissions). Once the fibers are incorporated into the mud, however, airborne
releases are unlikely to occur. The free-fiber releases will probably settle
on the ground or be washed by rain from the air and eventually become stabil-
ized in ground or river sediments. It should be noted that most drilling
sites are located remote from population centers. Meylan, et al.,11* have
estimated that perhaps 0.5 percent of the asbestos consumption for drilling
fluids is lost to the air during onsite mixing. Since 4900 metric tons are
248
-------
consumed annually, 24.5 metric tons of fibers would become airborne. This is
higher than process and disposal emission estimates arrived at for the entire
miscellaneous products category using Levine's31 assumptions. Combining
Levine's 1974 estimates with 1980 asbestos consumption data, an estimate of
5.2 tons per year for process emissions and 0.5 tons per year for disposal
emissions can be calculated. For consistency with the other chapters, these
estimates will be used for the entire miscellaneous products category. The use
of pelletized asbestos by the entire industry would significantly reduce the
amount of asbestos released to the air.
Conclusion
The use of asbestos in drilling muds has been decreasing due to concern
for worker's health and standards promulgated by the Occupational Safety and
Health Administration concerning airborne asbestos. In instances where
asbestos is used, asbestos in pellet form, as opposed to fiber form, should
be employed to decrease fiber release to the air. The ultimate disposal of
asbestos containing drilling muds is in the mud pit which is covered with
dirt.
Adequate substitutes are available to replace both functions of asbestos
in drilling muds, i.e., to provide carrying capacity (viscosifier) and to act
as a loss-circulation material. A large number of substitutes exist for loss-
circulation material at a competitive cost. The substitute materials which
are viscosifiers are the bentonite, attapulgite, and sepiolite clays and a
variety of polymers. The clays are competitive with asbestos in cost. The
polymers are more expensive than asbestos, but less material is necessary to
make up the drilling mud resulting in a cost per barrel figure that is still
more expensive, but nevertheless competitive. The use of asbestos in drilling
muds is not mandatory and probably not even necessary in most applications as
adequate substitutes exist at a competitive cost.
SHOTGUN SHELL BASE WADS
Asbestos has been used to manufacture base wads for shotgun shells. Base
wads are formed from a mixture of about 36 percent by weight of asbestos, 54
percent wood flour and 10 percent wax which is pressed to form the required
shape.18
Only one shotgun shell manufacturing plant (operated by Remington Arms
Company in Bridgeport, CT) is known to use asbestos. However, the manufacturer
is currently phasing out asbestos in shotgun shell base wads. The asbestos-
containing shells are being replaced with a one piece polyethylene shell which
is a more stable shell in addition to being less costly. The Remington Arms
Company recently reported that they will have converted 95 percent of the
asbestos-containing shotgun shells to one piece asbestos-free shells by the
end of the year 1980. The remaining 5 percent will be converted to asbestos-
free shells by the end of the year 1981.18
The major source of emissions from manufacturing occurs during handling
and introduction of the raw material. Processing areas are typically vented
to fabric filters. The material collected in the baghouse is recycled.
Fiber release in process water and product scrap wastes are judged to be
minor. Also, fiber emissions probably occur when the shotgun shell is fired
from a gun but there is presently no means of determining the amount of
fibers that become airborne as opposed to those that remain encased in the
wad mixture.11*
249
-------
ASPHALT/ASBESTOS CEMENT
Asphaltic cement consists of aggregates cemented together with ordinary
paving grades of asphalt such as AC-10 and AC-20.1^ The idea behind adding
asbestos to asphaltic cement was to increase the amount of asphalt that could
be put into the mix, which would increase the strength of the material and
increase the life of the pavement.20 While there is some indication that
asbestos might improve the quality of asphalt cement, the prevailing opinion
appears to be that if there is actually anything to be gained by adding
asbestos, it isn't enough to make it worthwhile. A spokesman for the National
Asphalt Paving Association said that there was evidence that asbestos might
actually be an agent contributing to cracking.19 In a recent survey, individ-
uals associated with asphaltic cement manufacture and use were not aware of
any intentional use of asbestos in asphalt paving in the United States.21
The only place where asphalt/asbestos cement is known to be used in North
America is Canada.
FOUNDRY SANDS
Foundry sands are used to make expendable molds for metal castings. The
sand is used with a bonding agent to give the mold the necessary strength re-
quired for castings. The mold is filled with metal through a system of channels
called runners or gates. In addition, there is a system of risers which ensure
that the mold is properly filled and compensated for shrinkage.
Asbestos is an undesirable material in foundry sands since it lowers
the refractory point of the sand mold. For this reason, asbestos is not
used in foundry sands for making molds for the production of castings.22
Personnel from the American Foundryman's Society as well as suppliers of
foundry sands and asbestos stated that asbestos is not used in foundry sands
at this date.23-26
Asbestos has been used in the past as a filler in the formulation for
the manufacturing of insulating sleeves for risers on castings. However^
as a result of Occupational Safety and Health Administration (OSHA) standards for
airborne asbestos in the workplace, asbestos use for insulating sleeves or
risers has ceased.22'23
Substitute materials for asbestos fibers used in insulating sleeves on
risers for castings include any inert mineral material that can: (a) with-
stand high heat, (b) insulate, and (3) does not crystalize with water at
high temperatures. The materials used to manufacture the insulating sleeves
for risers on castings are proprietary but include such mineral compounds as
vermiculite, perlite, and diatomaceous earth.22
SPRAYED-ON INSULATION
The use of asbestos in sprayed-on insulation was regulated in 1973 by
the National Emission Standard for Asbestos (40 CFR 61) promulgated by the
U.S. Environmental Protection Agency. This standard limits the amount of
asbestos in spray-on materials used to insulate or fireproof buildings,
structures, pipes, and conduits to less than one percent asbestos on a dry
weight basis. This standard effectively eliminated the use of asbestos as
sprayed-on insulation. The one percent limitation prevents the use of asbes-
tos while allowing the use of other materials in which asbestos is a trace
250
-------
contaminant. In 1978, the standard was revised to limit the use of sprayed-on
asbestos for decorative purposes to materials containing less than 1 percent
asbestos.
Prior to 1973, it had been common practice to coat pipes, ducts, boilers,
tanks, reactors, turbines, furnaces, and structural members with sprayed-on
asbestos materials.27'28 At present, however, the major source of asbestos
fiber emissions is during demolition of existing structures and manufacturing
equipment. The National Emission Standard for Asbestos requires removal of
asbestos insulation before demolition with adequate wetting of all exposed
asbestos during the removal process.
It has been estimated that about 450,000 metric tons of installed asbestos
insulation may be in place.29 Wear and release of asbestos fibers from in-
stalled insulation were calculated at a rate of 0.05 percent per year of total
installed tonnage. The release of fibers into the building atmosphere has been
found to be greatest from contact such as maintenance and reentrainment during
custodial activities such as heavy dry dusting, sweeping and vacuuming. As-
bestos emissions from these and other situations are compared in Table 61.
Comparison of the optical microscope measurements in this table suggest that
high optical microscope counts relative to the fiber concentrations on a weight
basis may be largely due to the presence of nonasbestos fibers. More extensive
measurements are needed to characterize the collected fibers and to determine
the extent of this asbestos exposure risk.
ARTIFICIAL FIREPLACE ASHES AND ARTIFICIAL SNOWS
Between 1971 and 1976, over 100,000 logs for gas-burning fireplace sys-
tems were reported sold which were frosted or treated with asbestos-containing
materials. At approximately 1/2 pound of asbestos per log, approximately 4.5
m.t. of asbestos, mostly chrysotile, were sold annually for artificial embers.14
In mid-1977, manufacturers stopped producing the product in anticipation of a
subsequent consumer ban by the Consumer Products Safety Commission. The ban
of artificial emberizing materials (ash and embers) containing respirable free-
form asbestos became effective December 15, 1977. Manufacturers of artificial
gas log amberizing material are currently using four substitutes in their
products: vermiculite, rock wool, mica, and synthetic fibers.30 Health con-
siderations have also nearly halted the use of asbestos in artificial snows.
CONCLUSION
The use of asbestos in the miscellaneous products discussed in this sec-
tion has nearly been disconstinued. Concerned with worker safety, the Occupa-
tional Safety and Health Administration has imposed regulations on the handling
of asbestos at manufacturing facilities. The cost of complying with these
regulations has tended to encourage the use of alternative fibers where asbes-
tos had been used because it was cheap and convenient. Products such as foundry
sands for special mold applications have readily adopted other materials. A
few products have been forced out of the market by health concerns. This is
especially true for decorative, nonessential products such as artificial snows.
251
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TABLE 61. AIRBORNE ASBESTOS IN BUILDINGS29
Sampling conditions or situation
Mean counts
(f/cc )
[O.M.]
Number of
samples
Standard
deviation
University dormitory, UCLA
0.1
-
0 to 0.8
Exposed friable surfaces, 98 percent
amosite
General student activities
(range)
Art and Architecture Building, Yale
University—Exposed friable ceilings,
20 percent chrysotile
Ambient air, City of New Haven
0.00
12
0.00
Fallout
Quiet conditions
0.02
15
0.02
Contact
Cleaning, moving books in stack area
15.5
3
6.7
Relamping light fixtures
1.4
2
0.1
Removing ceiling section
17.7
3
8.2
Installing track light
7.7
6
2.9
Installing partition
3.1
4
1.1
Reentrainment
Custodians sweeping, dry
1.6
5
0.7
Dusting, dry
4.0
6
1.3
Proximal to cleaning (bystander
exposure)
0.3
—
0.3
General Activity
0.2
36
0.1
Office buildings, Eastern Connecticut
Exposed friable ceilings, 5 to 30
percent chrysotile
Custodial activities, heavy dusting
2.8
8
1.6
Private homes, Connecticut
Remaining pipe lagging (dry) amosite
and chrysotile asbestos
4.1
8
1.8 to 5.8
(range)
Laundry: contaminated clothing
Chrysotile
0.4
12
0.1 to 1.2
(range)
(continued)
252
-------
TABLE 61. (continued)
Sampling conditions or situation
Mean counts
(f^cc ) Number of Standard
[O.M.] samples deviation
Office building, Connecticut
Exposed sprayed ceiling, 18 percent 79
chrysotile
£
Under asbestos ceiling 99
Remote from asbestos ceiling 40c
Urban Grammar School, New Haven
Exposed ceiling, 15 percent chrysotile
asbestos
Custodial activity: sweeping, vacuuming 643°
Apartment Building: New Jersey, heavy 296
housekeeping
Tremolite and chrysotile
Office buildings, New York City
Asbestos in ventilation systems 2.5 to 200
Quiet conditions and routine activity
2
1
40 to 110
(range)
186 to 1100
(range)
0 to 800
Nanograms/cubic meter, determined by electron microscope.
253
-------
Where regulation has been unable to indirectly halt manufacture of an asbestos
product, the Consumer Product Safety Commission has imposed bans of specific
product categories for use in the consumer sector.
The only miscellaneous industry where asbestos fiber is still used is in
oil and gas drilling. When asbestos is used in drilling muds, pelletized as-
bestos is the preferred choice over raw fibers since pelletized asbestos gen-
erates less fiber release to the air during the opening and emptying of bags
and mixing. The future of asbestos use in drilling muds, however, is uncer-
tain because adequate substitutes are available to replace the functions of
asbestos for this application.
Many of the miscellaneous products using asbestos have short service
lives and are discarded to a dump or landfill in a bound fiber form after
only a few years of service. Although products such as spray on insulation
have been banned, they will likely be of concern for health reasons for years
to come. Asbestos containing insulation in place in schools, factories,
offices and homes will continue to be a potential hazard to a high percentage
of the population. Also as structures containing asbestos materials are de-
molished, free fibers may be emitted even in controlled situations.
254
-------
REFERENCES
1. Clifton, R. A. Asbestos—1979. U.S. Department of the Interior.
July 1979.
2. Clifton, R. A. Asbestos. 1980 Minerals Yearbook. U.S. Bureau of Mines,
Washington, D.C.
3. Huebotter, E. E. and G. R. Gray. Drilling Fluids. Kirk-Othmer Encyclo-
pedia of Chemical Technology. Second edition. Volume 7. pp. 287-307.
4. Zwicker, D. A. Glorious Mud, The Lamp, Exxon Corporation, New York, NY.
Volume 61, No. 4, Winter (1979). pp. 26-29.
5. Pundsack, P. L. and W. 0. Jackson. Fibers, Inorganic. Encyclopedia of
Polymer Science and Technology. Volume 6, pp. 671-690. John Wiley and
Sons, Publishers, NY.
6. Letter from B. J. Pigg, Asbestos Information Association to Lester Y.
Pilcher, GCA/Technology Division, February 13, 1980. Amount of Asbestos
used annually in Drilling Mud.
7. Binder, G. Exxon Production Research Company. Houston, TX.
(713) 965-4810, Personal communication with Lester Y. Pilcher, GCA/
Technology Division. January 24, 1980. Notebook No. 04, Phone call
No. 7.
8. Wright, T. R., Jr., and W. Dudley, Jr., ed. Guide to Drilling Workover,
and Completion Fluids. World Oil. p. 116. June 1979.
9. Kennedy, B. Messina, Inc. Dallas, TX. (713) 225-6383, personal com-
munication with Lester H. Pilcher, GCA/Technology Division, January 29,
1980. Notebook No. 04, Phone call No. 11.
10. Drilling Fluids: Computer Planning and New High-Temperature Fluid.
World Oil. December 1979.
11. Fenner, E. Johns-Manville Corporation. Denver, CO. (303) 979-1000,
personal communication with Lester Y. Pilcher, GCA/Technology Division,
January 30, 1980. Notebook No. 04, Phone call No. 13.
12. Clear, E. E. Drilling Specialties, Bartlesville, OK. (918) 661-5405,
personal communication with Lester Y. Pilcher, GCA/Technology Division,
February 4, 1980. Notebook No. 04, Phone call No. 22.
255
-------
13. Petri, C. Montello, Co. Tulsa, OK (918) 665-1170, personal communi-
cation with Lester Y. Pilcher, GCA/Technology Division, February 4, 1980.
Notebook No. 04, Phone call No. 20.
14. Meylan, William M. et al. Chemical Market Input/Output Analysis of
Selected Chemical Substances to Assess Sources of Environmental Contam-
ination: Task III. Asbestos. Prepared for OTS, EPA, Washington, D.C.
15. American Petroleum Institute. Oil and Gas Well Drilling Fluids. API
Bulletin 13F, Washington, D.C. August 1978. p. 6.
16. Daly, A. R., et al. Technological Feasibility and Economic Impact of
OSHA Proposed Revision of the Asbestos Standard (Construction Excluded).
Asbestos Information Association/North America. March 26, 1976.
17. Bradfield, R. E. N. Asbestos: Review of Uses, Health Effects, Measure-
ment and Control. Atkins Research and Development, Epsom Surrey, England.
January 1977.
18. Telecon. T. McCawley. Remington Arms Corp. Bridgeport, CT with
R. Bell, GCA Corporation, GCA/Technology Division. 1980.
19. Foster, C. Consultant. National Asphalt Paving Association. Riverdale,
MD. (301) 779-4880, personal communication with S. Duletsky, GCA
Corporation, February 11, 1980. Notebook No. 05, Phone call No. 49.
20. Leman, M. Johns-Manville Corporation. Denver, CO. (303) 979-1000,
personal communication with S. Duletsky, GCA Corporation, February 14,
1980. Notebook No. 05, Phone call No. 58.
21. Plate, H. Manager of Marketing. ASARCO, Inc. New York, NY. (212)
732-9500, personal communication with S. Duletsky, GCA Corporation,
February 20, 1980. Notebook No. 05, Phone call No. 60.
22. Kotzin, Ezra. American Foundryman's Society. Des Plaines, IL. (312)
824-0181, personal communication with Mr. L. Y. Pilcher, GCA/Technology
Division, February 15, 1980. Notebook No. 04, Phone call No. 39.
23. Mosher, Gary. Industrial Hygienist. American Foundryman's Society.
Des Plaines, IL. (312) 824-0181, personal communication with Mr. L. Y.
Pilcher, GCA/Technology Division, February 12, 1980. Notebook No. 04,
Phone call No. 33.
24. Kuhn, S. Johns-Manville Regional Sales Office. Atlanta, GA. (404)
449-3300, personal communication with Mr. L. Y. Pilcher, GCA/Technology
Division, February 15, 1980. Notebook No. 04, Phone call No. 35.
25. Penters, A. Sales Manager. Whitehead Brothers Co. Florham Park, NJ.
(201) 377-9100, personal communication with Mr. L. Y. Pilcher, GCA/
Technology Division, February 12, 1980. Notebook No. 04, Phone call
No. 29.
256
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26. Marvel, H. Pennsylvania Foundry Supply and Sand Co. Philadelphia, PA.
(215) 333-1155, personal communication with Mr. L. Y. Pilcher, GCA/
Technology Division, February 15, 1980. Notebook No. 04, Phone call
No. 38.
27. Cavaseno, F. Latest Work on Asbestos Won't Be the Last. Chemical
Engineering. November 6, 1978. pp. 76, 80.
28. Reitze, W. B., et al. Application of Sprayed Inorganic Fiber Containing
Asbestos: Occupational Health Hazards. Am. Ind. Hyg. Ass. J. 1972.
Vol. 33, pp. 178-191.
29. Sawyer, R. N., and C. N. Spooner. 1978. Sprayed Asbestos-Containing
Materials in Buildings: A Guidance Document. Part 2. U.S. Environmental
Protection Agency. Research Triangle Park, North Carolina. EPA Report
No. EPA-450/2-78-014.
30. Part 1305—Ban of Artificial Emberizing Materials (Ash and Embers)
Containing Respirable Free-Form Asbestos. Federal Register, Chapter 11—
Consumer Product Safety Commission. December 15, 1977.
31. Levine, R., ed. Asbestos. An Information Resource. May 1978.
257
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SECTION 14
RESULTS, DISCUSSION AND CONCLUSION
RESULTS
The format of this report has been structured to assist the reader in
understanding the rationale for using asbestos fibers in each of the product
categories. In this regard each asbestos product is presented in the same
manner, with specific data on the product, its method of manufacture and po-
tential atmospheric emissions of asbestos that may result from its production.
This sequential presentation familiarizes the reader with all pertinent facets
of asbestos products and facilitates comparison between product categories.
For each product category, the composition of the asbestos product is
described, together with the uses and applications of the product and the
special qualities that have, to this time, made asbestos an indispensable
constituent of the product. This information provides the background infor-
mation on the product that is necessary if we are to understand why the prod-
uct is manufactured, the qualities the product must have to be commercially
viable and how asbestos fulfills this need. Once this background is tinder-
stood, the commercially available substitutes for the asbestos product are
discussed. These substitutes may take the form of a fiber by fiber replace-
ment for asbestos or they may be a completely new asbestos-free product. The
development and production of asbestos-free substitutes are dependent upon a
variety of changing factors including cost, customer preference, substitute
qualities and regulatory controls. Listing the currently available substitutes
serves to inform the reader of the type and extent of activity in this area.*
A discussion of product manufacture then follows in each section, detail-
ing the major points of fiber introduction and therefore potential fiber
release. Work practices and pollution control devices that are used to minimize
worker exposure to asbestos fibers are listed. The extent of emission control
helps quantify plant asbestos emissions and provides an indication of industry's
response to the potential health hazards posed with occupational exposure to
asbestos. In addition, the number and location of plants producing asbestos
products are listed, based on the best available data, for each product category".
Finally, the release of asbestos to air, water and land from the manufac-
ture, use and disposal of the asbestos products is discussed. Engineering
estimates have been made for the various potential releases to quantify total
annual asbestos emissions. As there are few published data on asbestos
emissions from the product categories, emission estimates can only be a quali-
tative statement on asbestos release. They should not be used as categorical
For more detail on asbestos substitute products, refer to "Asbestos Substitute
Performance Analysis," U.S. EPA, OPTS.
258
-------
emission quantities. Furthermore, these estimates are directly related to
1980 asbestos consumption data, which itself was an atypically low use year.
Neverthel.eus, in order to understand the magnitude of the asbestos problem
and to compare product categories, asbestos release rates must be quantified,
and numbers are assigned in this report to each avenue of asbestos release
to the environment. These and other emissions estimates will be subsequently
discussed.
Asbestos Release Potential
As discussed, the potential for release of asbestos fibers during the
life cycle of products in the major product categories can only be estimated
in general terms. Nevertheless, many useful conclusions are possible. Data
are summarized in Table 62. These data have been taken from the individual
product category chapters presented in this report.
The number of sources of asbestos fiber releases increases as one
proceeds from mining and mills to primary manufacturers to secondary fabri-
cators and on to users. There are four operating mines and associated mills
in the United States. There are approximately 130 major primary manufacturers
in the nine major product categories. There are many hundreds, perhaps
thousands, of secondary fabricators.
A complete documentation of the asbestos release potential at each of
these primary manufacturing plants would necessarily require individual site
inspections. This has not yet been done, and such a series of visits was
beyond the scope of this report. Nevertheless, generalized statements as to
the extent to which typical control measures are practiced for each product
category can be made based on published data and a few, select site visits.
These statements on asbestos release have been summarized by high, medium,
and low potential and appear in Table 62. This quantification of asbestos
release potential has been made for primary and secondary finishing, instal-
lation, use, removal and disposal. In addition, substitute availability is
also summarized in Table 62. While the fiber release potential at domestic
mines and mills is high, this area has not been a primary focus of this report
and is not reported here.
Fiber shipment, receipt, transfer to storage, and bag opening are common
to all product manufacturing facilities. Site visits indicate that there is
a wide variation in the extent of fiber release. The conditions of shipping
vehicles, loading docks, and storage areas varied from spotlessly clean and
free of visible fiber to filthy and coated with deposits of fiber. There
seems to be no consideration other than cost which prevents users of asbestos
from eliminating essentially all breakage and the resultant fiber release.
The use of plastic shrink-wrapping for asbestos fiber shipments and the pal-
letizing of asbestos fibers at the asbestos mills are gaining in popularity
throughout the asbestos industry. Such practices are proven methods of
minimizing fiber release from accidental spills. Until these packaging tech-
niques are adopted in each asbestos product industry, the asbestos release
potential will remain high at shipping, receiving and fiber transfer stations,
as listed in Table 62.
259
-------
TABLE 62. ASBESTOS RELEASE POTENTIAL2
Number of
manufac-
turing
locations
1°
Processing
2°
Process-
ing and
finish-
ing
Substitute
availability
Shipping
receiving
opening
Installation
Use
Demoli-
tion or
removal
Product
category
Min-
ing
Mill-
ing
Process-
ing
Finish-
ing
Dispo-
sal
Not
Good good
Number
Proper
Improper
Proper
Improper
1
Paper
18/1°
H
B
B
M
M
M-B
U(B)
U(B)
0(L)
D(M)
D(B)
0(L)
X*
2
Friction
products
34/1°
some 2°
H
H
B
L
B
B
L-M
L-M
L
-
M-H
L-M
X1*
3
A/C pipe
n/i°
H
B
fl
M
B
-
L
M-B
L
M
0
U
X
4
A/C sheet
5/1°
many'/2°
H
B
B
L
fl
H
L
M-B
L
-
U(L)
L
1?
5
Floor tile
10/1°
B
B
a
L
L
-
L
L
L
-
L-M
L
xc X
6
Gaskets and
packing
27/1°
many/20
H
B
H
L
M
B
L
-
L
H
L
L
X*5
7
Sealants
20/1®
0/2°
H
B
B
L
L
-
L
-
L
-
L
L
X*1
8
Plastics
7/1°
3000/2°
H
B
B
L
-
L-B
L
M-B
L
-
L
L
jX
-------
The next common stage in asbestos product manufacture is bag opening
and initial mixing of fibers with other ingredients. For products which can
tolerate pulpable kraft fiber, there is no need to open bags before mixing.
For other products, adequate control seems possible through the use of hoods
and automatic bag handlers with eventual landfllling of used bags. For wet
mix products a hydropulper is generally employed but the energy input rate
is higher. Batch mixing with a hydraulically closed cover on the pulper
appears to prevent fiber emission. For dry mix processes the potential for
fiber emission seems to be uniformly high.
For paper products, the fiber release potential is strongly dependent
on the binder or saturant employed. For starch bound papers release poten-
tial is high. For latex bound or asphalt saturated papers release potential
is lower. During the drying of paper, high volumes of air are passed over
the paper in the dryer section to carry off moisture. Depending on the
facility in question this dryer air may be vented to the outside directly,
vented to the outside after passing through heat recovery units or vented
back into the building for space heating. It does not seem to be a common
practice to pass this air stream through a baghouse. Finishing consists of
trimming and slitting with a possibility but not necessarily a high proba-
bility of significant fiber release. Due to the wide variety of products in
this category it is not possible to generalize on fiber release potential
during installation, use, demolition or disposal. There is a possibility that
removal of old commercial roofing (asbestos paper base) may result in sig-
nificant fiber releases.
The greatest fiber release potential association with asbestos-cement
pipe is not in the pipe production, where manufacturing processes are closely
monitored and controlled. It is in the field installation of the pipe, where
uncontrolled finishing techniques can lead to significant fiber emissions
that a problem exists. Abrasive disk sawing and drilling can release the
asbestos fibers from their cement matrix and lead to an emission of free as-
bestos fibers. In addition, asbestos-cement water mains when used with
aggressive water supplies can suffer a degradation of the cement binder and
subsequent release of asbestos fibers into the water.
Production of vinyl asbestos floor tile has a small fiber release poten-
tial as the asbestos fibers are encapsulated in a vinyl bonding agent which
seals them in. Removal of vinyl asbestos floor tiles by sanding might result
in some fiber release. While small quantities of fibers might be released
to the air and water by normal wear and tear of this product, no quantitative
measurement of fiber release from fresh, worn or weathered products were
found.
In friction products, asbestos cement sheet, gaskets, and plastics, the
fibers are contained in a rigid or semirigid matrix which has a low potential
for releases of high concentrations of fiber. For exposed asbestos cement
sheet building products, it is possible that the large area of exposed,
weathered product in old installations could result in the emission of signi-
cant numbers of fibers over time. For all of these rigid matrix products
261
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there is a high potential for fiber release during energy-intensive fabrica-
tion steps such as sawing, drilling, or grinding. This is especially true
with regard to millboard and rollboard.
Since there is little binder used in conjunction with the raw asbestos
fibers, packings and textiles have a high potential for fiber release when-
ever they are handled, especially when abraded.
Worker Exposure
The current OSHA occupational standard for asbestos is 2 f/cc for an
8-hour time weighted average (TWA). In-plant measurements of asbestos con-
centrations have been taken at several asbestos products manufacturing fa-
cilities. These data have been presented throughout this report and are
summarized in Table 63. Most of these data were measured prior to the ef-
fective date of the OSHA regulation, therefore they should not be used as a
measure of compliance with this regulation. Rather, these data provide a
relative measure of asbestos concentrations at various process points within
a facility. As noted on Table 63, for all product categories the highest
asbestos exposure is at the shipping, receiving and bag opening stations.
This is consistent with the previously described high exposure potential at
these areas where the raw fiber is handled and introduced into the system.
Exposure at processing stations drops dramatically for products, such as
paper, A/C pipe and sealants, where the fiber is encapsulated by a binder.
Conversely, for textiles the measured asbestos concentration for processing
increases due to the continued unaltered presence of the asbestos fiber.
Concentrations at finishing stations are close to those of processing points,
with some products showing an increase as the product is cut and machined to
final specifications. Secondary processing exposure is virtually identical
to that of primary finishing, with the exception of A/C pipe, where improper
installation techniques may cause localized elevated asbestos levels. Finally,
a qualitative estimate has been made as to the exposure that results from
installation, use, demolition and disposal of each product, and this is re-
ported in Table 63 as well.
Control of fiber release can be achieved through manufacturing equipment
design, fabricating equipment design, add-on pollution control equipment,
work practices and use practices. Control efforts instituted to date have been
made in response to health effects knowledge as formalized in OSHA and NESHAPS
standards. Higher degrees of control (at increased cost) are certainly pos-
sible for many of the asbestos release points in each product life cycle.
DISCUSSION AND CONCLUSION
Quantification of asbestos emissions from the production, use and disposal
of asbestos-containing products is at best an inexact science. There is
little published data in this area and the few relevant articles often differ
by orders of magnitude in their emissions estimates. This report has attempted
to use these estimates by modifying them with engineering evaluations of the
extent and effectiveness of emissions control in the asbestos products industry
today. In addition, these data have been upgraded to account for 1980 asbestos
262
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TABLE 63. EXPOSURE DATA (TYPICAL fibers/cc TWA)a - 1975
1* Processing
Installation
Number
Product
cateRory
Mining
Milling*
Shipping
receiving
opening
Processing
Finishing
11
Processing
Proper
Improper
Uae
Demolition
Disposal
1
Paper
a
a
1.9
0.8
1.0
D
U(H)
U(H)
U
U
0
2
A/C pipe
H
H
3.6
0.9
1.3
2.5
h
L-M
L-M
M
L
3
Floor tile
B
a
3.0
3.0
-
-
L
L
1.2d
U
U
*
Friction
products
H
H
2.5
2.3
2.0
2.0
L-M
L-M
M-H
M-H
L-M
5
Sealants
H
H
2.5
1.0
-
-
L
-
L
L
L
6
A/C sheet
H
a
2.0
2.0
2.0
2.0
L
H
L
L
L
7
Gaskets and
packing
H
a
1.5
0.5
-
U
L
-
U
U
U
8
Plastics
H
a
1.5
1.1
1.0
1.0
L
H
L
Jf
uf
9
Textiles
H
H
• 2.5
4.0
3.0
-
U
U
0.01
L
L
10
Miscellaneous
H
a
1.5
M
-
-
U
D
L-M
L
L
KEY
H * high L =» low
M " cedlusa D = unknown
aOptical nicroscope fibers.
^Drillers have the highest nlnlng exposures.
cBlenders, baggers and packers have the highest willing exposures.
^Froa sanding operations on Installed floors.
eThese products would norsally be discarded while still whole, as In parts in old autos, etc.
^Estioates Indicate that baghouse fine emissions may take place but the scrap product
asbestos fibers would be well bound.
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consumption. Nevertheless, the emissions data provided in this report should
only be considered refined estimates. Substantial sampling and analysis work
needs to be done at and around asbestos manufacturing facilities to provide a
true measure of ambient asbestos release today.
A summary of the asbestos release data presented in this report is
presented in Table 64. An examination of the data in this table indicates
that the overwhelming majority (98.2 percent) of asbestos fibers released
to the environment from manufacturing are deposited on the land. This re-
lease is in the form of product scrap, baghouse and vacuum cleaner dust and
sludge from industrial water effluent clarifiers. If properly disposed of
in a regulated sanitary and/or hazardous waste landfill, this asbestos will
not represent an additional environmental hazard. Waterborne asbestos repre-
sents the second largest emission, with approximately 95 metric tons per year being
! carried away in plant effluent. The fate of this emission is unknown. Some
of this asbestos may be subsequently removed from the industrial discharge
by municipal wastewater treatment plants. From here it is either landfilled
or burned in a sludge incinerator. No data are available to estimate the
exact fate of this waterborne asbestos. Air emissions, both from process
and disposal operations make up the smallest amount in terms of annual tons
emitted. Yet this asbestos is potentially the greatest health ^Foblem,"as
it can be carried great distances by the wind and a portion of it may be inhaled
by the general populace. More work in this area is needed to quantify the cause
and affect relationship between plant asbestos emissions and population exposure
to asbestos fibers.
This report has traced the fate of asbestos in the industrial and com-
mercial sectors of society from its introduction into the plant to final
use and disposal. Atmospheric emission rates have been estimated for air,
water and land disposal. Data on asbestos exposure resulting from use of
the final asbestos product is still too inconclusive to be quantified. As
the scientific community learns more about the potential health hazards asso-
ciated with asbestos use and regulatory action in this area is increased,
additional environmental controls will be adopted to minimize asbestos
release. Occupational exposure levels have initially received the most
attention and asbestos fibers today are generally carefully controlled within
the plant environment. As the emphasis shifts toward nonoccupational exposure
to asbestos, additional controls in this area will be adopted. States, such
as Connecticut, are considering adopting an ambient air quality asbestos
standard. This increased awareness of the problems associated with asbestos
will help ensure that all asbestos fiber release in the future is minimized
and carefully monitored.
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TABLE 64. GCA ESTIMATES OF ASBESTOS RELEASE FROM MANUFACTURING AND DISPOSAL
TO AIR, WATER AND LAND, IN Mt/yr - 1980
Air
Product
category
From
process
From
disposal
Water
Land
Total
Paper
Friction
A/C pipe
A/C sheet
Floor tile
Gaskets and packing
Sealants
Plastics
Textiles
Miscellaneous
Totals
45
10.9
14
0.8
3.6
6.1
0.5
a
0.3
5.2
86.4
(0.8%)
4.5
2.2
7
0.4
2
0.6
0.5
0.1
0.1
0.5
17.9
(0.2%)
45
13.1
34
1.8
0.7
4,451.5
1,111.9
3,599
198
939
307
109
38
48
94.6
(0.9%)
10,801.4
(98.1%)
4,546
1,138.1
3,654
201
944.6
313.7
110
38.1
49.1
5.7
11,000.3
100%
Minimal amounts.
^Differs slightly from Table 8 estimates due to rounding off.
"Unknown.
265
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GCA-TR-79-7 3-G
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Toxic Substances
Washington, D.C.
Submitted in Partial Fulfillment of
Contract No. 68-02-3168
Technical Service Area 3, Work Assignment No. 18
EPA Project Officer
James Bulman
LIFE CYCLE OF ASBESTOS IN COMMERCIAL
AND INDUSTRIAL USE INCLUDING ESTIMATES
OF RELEASES TO AIR, WATER AND LAND
Final Inhouee Report
February 1982
Prepared by
David Cogley
Nancy Krusell
Robert Mclnnes
Peter Anderson
Ronald Bell
GCA CORPORATION
GCA/TECHNOLOGY DIVISION
Bedford, Massachusetts
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