FILE COPY OSSI*. “77-/ZS^CRO

DO NOT REMOVE

“TSTReTport on the Fiber Content

of Eighty Industrial Talc

Samples Obtained from, and

Using the Procedures of, the

Occupational Safety and

Health Administration

trait) fi-r

n its - ' - 77

•'J& i tm LOTP

Prepared for Occupational Safety and Health Administration

Department of Labor

Washington, D. C. 20212

Prepared by the Staff of the

Analytical Chemistry Division, P. D LaFleur, Chief

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

May 1977

A REPORT ON THE FIBER CONTENT

OF EIGHTY INDUSTRIAL TALC

SAMPLES OBTAINED FROM, AND

USING THE PROCEDURES OF, THE

OCCUPATIONAL SAFETY AND

HEALTH ADMINISTRATION

Prepared for Occupational Safety and Health Administration

Department of Labor

Washington, D. C. 20212

Prepared by the Staff of the

Analytical Chemistry Division, P. D. LaFleur, Chief

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

May 1977

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Acting Director
This document has been prepared for the

Occupational Safety and Health Administration

of the Department of Labor. Responsibility

for its use rests with that agency.
I. INTRODUCTION

A. Purpose of Study

This report has been prepared in response to a request received by Dr. John D. Hoffman, Director of the

Institute for Materials Research of the National Bureau of

Standards (NBS) , in a letter dated September 1, 1976, from

Dr. Morton Corn, Assistant Secretary of Labor, Occupational

Safety and Health Administration (OSHA) . In that letter.

Dr. Corn stated that analysis of talc samples for their

asbestos content was being performed by OSHA and the National

Institute of Occupational Safety and Health (NIOSH) but that

the methodology was being challenged by some of those regulated

by OSHA.

Dr. Corn indicated that his request to NBS was composed

of two tasks:

(1) to resolve the variability in the definition of

asbestos fibers in talc, and

(2) to determine the asbestos content of some 80 talc

samples to be provided by OSHA.

Copies of the letter containing this request and the subsequent

correspondence between Drs. Hoffman and Corn which provide

further background information, are included in this report

as Appendix I.

It was agreed by both parties that the first of these

tasks, i.e.y resolving the variability of the definition of

asbestos fibers, would be a complex, long-term program which

would require input from a number of sources both in the

private and public sectors. In view of this, it was agreed

that the more limited task, that of determining the asbestos

content of the OSHA talc samples, would be addressed by NBS

first. As Dr. Corn pointed out in his letter of October

8, 1976, this was recognized not to be a research task but

would involve an analysis performed according to the procedures

given in 29 CFR 1910.1001.

1
29 CFR 1910.1001 [39 FR 23502, June 27, 1974, as

amended in 41 FR 11505, March 19, 1976] deals exclusively

with airborne asbestos and does not describe procedures for,

nor make any reference to asbestos in talc. It does, however,

include the following two paragraphs which are pertinent to

the work discussed in this report:

"(a) definitions . For the purpose of this

section, (1) 'Asbestos' includes chrysotile,

amosite, crocidolite, tremolite, anthophyllite

,

and actinolite.

(2) 'Asbestos fibers' means asbestos

fibers longer than 5 micrometers.

"(e) Method of measurement . All determinations

of airborne concentrations of asbestos fibers shall

be made by the membrane filter method at 400-450 X

(magnification) (4 millimeter objective) with phase

contrast illumination."

These regulations do not, however, describe a measurement

procedure but rather prescribe a method of measurement

[viz., phase contrast microscopy). A procedure contains a detailed listing of the sampling of the material, the

specific experimental steps to be performed during an analysis,

and, often, descriptions of the mathematical calculations to

be performed and of the format for reporting results and

their associated errors. A method of measurement is defined

by a very general statement of the type of measurement to be

made, from which a specific procedure is developed.

Since 29 CFR 1910.1001 stipulates only that the method

of phase contrast microscopy is to be used for the determination of asbestos, NBS requested a detailed procedure from

OSHA. In response, NBS was provided with a copy of the OSHA

document "Asbestos Fiber in Air" - Method No. P$CAM 239,

2
\ issued March 30, 1976. NBS was also informed that the

determination of asbestos, including asbestos in talc, was

performed at the OSHA Salt Lake City, Utah, laboratory

(OSHA-SLC), using P$CAM 239. Method No. P§CAM 239, however,

deals only with the determination of asbestos in air using

phase contrast microscopy to examine membrane filters.

Since the determination of asbestos in talc is not described

in the document, NBS was told to contact Mr. Willard C. Dixon

at OSHA-SLC to obtain an exact description of the procedure

used on talc samples.

To become familiar with the asbestos in talc procedure,

an NBS scientist then visited the OSHA-SLC laboratory and

obtained verbal and written descriptions of the procedure

used. He spent approximately one and one-half days at the

laboratory observing the procedures and techniques used and

discussing them with the OSHA employees. At the conclusion of

the visit he wrote a detailed report of what he had observed.

This report was submitted to Mr. Dixon for comment. A copy

of the report is included as Appendix II to this document.

The portions of the report that are enclosed in boxes are

the comments added by OSHA-SLC personnel.

NBS scientists also discussed the analysis of talc with

a number of other persons. Those contacted are listed in

Appendix III to this report.

Prior to commencing the actual analysis of the 80 talc

samples, we were assured by OSHA personnel that 29 CFR

1910.1001, P§CAM 239 and the annotated NBS trip report were

the only documents appropriate for documenting the analytical

procedure to be employed, and that the process followed by

NBS in developing the detailed procedure was proper.

v

3
The detailed procedure followed at NBS is given in

Section II of this report; however, a brief description of

the procedure, and some comments, are given below:

Phase contrast microscopy, with a mounting medium

having an index of refraction of 1.546, is used. Both

fibers (a fiber being defined as having a minimum

length of 5 ym, a maximum diameter of 5 ym, and a minimum length to diameter ratio of 3:1) and other

particles are counted.

Early in the study we determined that the identification of "asbestos” with the procedure used was

extremely difficult for the following reasons:

(1) Since phase contrast microscopy is only a contrast mechanism, it does not indicate the degree of

difference between the refractive index of the liquid

and a particle or fiber. For example, if a specimen is

mounted in a liquid which matches a refractive index of

chrysotile, then the particles and fibers counted would

include all fibers which do not have that particular

refractive index, e.g. s talc, anthophyll ite , wollastonite

,

fiber glass, etc. The same would be true for any other

liquid used.

(2) Most mineral species have three refractive

indices, therefore, any mineral fiber not lying in the

correct orientation for the selected liquid will not

match and would be visible and would be counted.

(3) The amphiboles are end members in solid

solution. As a result there may be a large range of

refractive indices from one end member to another. One

example of such a series would be the tremolite-actinolite

solid solution.

4
(4) In addition, the most common methods of talc

formation are the hydrothermal alteration of ultrabasic

rocks such as serpentine and tremolite and the thermal

metamorphism of siliceous dolomites. Therefore, during

the formation of talc in contact with other minerals,

there may be extensive interconversions between talc

and the minerals serpentine, tremolite and anthophyllite

.

These interconversions may give rise to single particles

which have a combination of the talc, anthophyllite,

and serpentine mineral phases.*

(5) There are many materials which may be present

in talc which have overlapping refractive indices,

e.g. 3

Mineral Refractive Index

Wollastonite 1.63

Tremolite 1.599 - 1.637

Quartz 1.55

Talc 1.539 - 1.589

Chrysot ile 1.493 - 1.567

(6)

Even if the refractive indices were known,

positive identification of minerals could not be made

since there may be interferences from other materials.

* Deer, W. A., Howie, R. A.,

Minerals 3 Vol . 3, Longmans,

England (1967) pp . 126-128.

and Zaussman,

Green and Co.

J . , Rook Forming

Ltd, London,

5
In his first letter to NBS, Dr. Corn requested a determination of the "number of fibers per unit weight or

unit volume. Also, the asbestos content as percent of total

weight...". This was to be based upon the definition of

asbestos to be resolved by NBS. Since the definition of

asbestos is to be investigated as part of the longer study,

reporting results obtained in these analyses in terms of

"asbestos" was not possible. The procedure used by OSHA-SLC

did not use weight or volume of total sample, but instead

used percent fibers as a function of total numbers of

particles on a slide; that convention was followed at NBS.

Thus, all data given in this report are on the basis of

numbers or percent of fibers per total number of entities

(particles plus fibers) counted (this is referred to as

number percent')

.

B. Goal of the Study

In view of the current limitations both in the definition

of asbestos and in the ability to distinguish minerals by the

OSHA methods using the existing definition of asbestos, NBS

established as the goal for this portion of the study to

analyze the 80 talc samples supplied by OSHA to NBS and to

report the number percent (and, if possible, the limits of

error) of fibers using the phase contrast optical microscopy

procedure discussed above and outlined in detail in Section

II below.

6
II. Analysis Procedure

1. Equipment used by NBS

a. A Leitz* Ortholux 1 microscope equipped

with lOx and 40x phase contrast objectives

and a phase contrast condenser.

b. Cargille refractive index liquid

2 5 °C (mounting medium) n = 1.546

c. Porton Reticle

d. lOx Periplan oculars

2. Specimen Mounting Procedure

Two drops of the mounting medium were placed on

a clean microscope slide.

The end of a new (clean) metal wire (paper clip)

was dipped into the mounting medium on the slide

and then into the sample which was contained

in a bottle.

The material adhering to the wire was blended

into the mounting medium on the slide.

A cover slip was then placed over the preparation.

Note: No attempt was made to homogenize the

contents of the sample bottle prior to drawing

the specimen. A vigorous blending or mixing

could itself lead to mechanical breakdown of

particles into fragments with fibrous appearance or the separation of one fiber into many

fibers. NBS did not attempt to homogenize

* In order to describe materials and experimental procedures

adequately, it is occasionally necessary to identify the

sources of commercial products by the manufacturer's name.

In no instance does such identification imply endorsement

by the National Bureau of Standards, nor does it imply

that the particular product is necessarily the best

available for that purpose.

7
the samples as the OSHA-SLC procedure does

not include homogenization.

3. Sample Notation

Upon receipt of the samples, a scientist who was

not involved in the analysis divided the samples and assigned

internal NBS numbers. This prevented the analysts from

knowing which of the 80 samples they were dealing with and

permitted blind replicate analyses.

Note: In the original transfer of the

samples from OSHA to NBS a list was inadvertently included which gave the sample identifications. As soon as this was discovered, the list was sealed in an envelope and placed

in the NBS Security Office safe until it was

returned to OSHA. The only person at NBS

who saw the list did not participate in any

any of the analytical work.

4. Microscopy Techniques

Phase contrast microscopy was the method used by

NBS, since it is the only technique specified both in

29 CFR 1910.1001 and in OSHA Method No. P$CAM 239. The

detailed procedure followed by NBS is described below. Any

steps which differ from the OSHA-SLC procedure are noted.

(1) Before the analysis of a specimen was performed,

the microscope illumination was adjusted for Kohler illumination, the annular diaphragm and phase- shifting elements

were aligned and the Porton reticle was calibrated against a

stage micrometer. The configuration of a Porton reticle is

shown in figure 1. A detailed description of both the

calibration and use of this reticle is given in P§CAM 239.

8
(2) The counting field was defined as the six rectangles on the left half of the Porton reticle.

(3) Fiber dimensions were determined by comparing the

length and width to the diameters of the calibrated circles

on the Porton reticle.

(4) The unknown samples were mounted as described above

in a Cargille liquid with a refractive index of 1.546.

Note: OSHA mounted their samples in liquids

9 s °r with n equal to 1.546 and 1.47. The

1.546 index was used to identify quartz and

ohry sotile which appear blue in bright- field

observation with their Zeiss phase-contrast

microscope > while the background is light

brown and most other materials are brown or

black. The 1.47 refractive index liquid is

carried over from techniques for identifying

airborne fibers collected on membrane filters

as opposed to the 1.546 liquid used for talc

analysis

.

(5) Counting fields were selected by advancing the

mechanical stage in a pattern of traverses of the slide in

one axis and steps along the other axis resulting in a rectangular zig-zag pattern. This procedure was followed

until the necessary number of fields was counted.

(6) NBS used the definition of (asbestos) fibers,

discussed above, viz. y a fiber is greater than or equal to

5 ym in length, has a length to width ratio of at least

3 to 1 , and has a maximum diameter of 5 ym. Any particle

meeting these criteria was counted as a fiber.

9
(7) The samples were continuously viewed over the range

of focal planes covering the sample thickness during the

counting

.

(8) A preliminary scan of the slide was performed to

attempt to find fibers in the specimen. If a fiber was found

the following counting procedure was performed on newly

prepared slides. Fibers were counted in as many fields as

necessary to yield a total fiber count of 100 with the

following exceptions:

(a) The analysts counted at least 20 fields

even if they counted more than 100 fibers,

and

(b) they stopped at 100 fields even if they did

not count 100 fibers.

(9) For fibers and particles that crossed either one

or two sides of the counting field, the following procedure

was used to obtain a representative count:

The analysts counted all particles or any fibers of the

correct dimensions which:

1. Were entirely within the counting area, or

2. Crossed the left or bottom sides, or

3. Crossed the upper or lower left corner, or

4. Crossed both the top and bottom sides.

Any other fibers and particles were not counted.

(10) When particle agglomerates covered a large portion

of the field of view, the field was rejected and replaced by

a new one.

(11) The measurements at NBS were performed 0 500x

magnification. OSHA measurements were done 0 400x to 450x

magnification, but NBS could not duplicate that magnification

with the equipment available. Calculations performed

indicate that the differences in magnification would not

result in any significant changes in the number of fibers

and particles identified.

10
\ (12) The numerical aperture, NA, of the NBS objective

was 0.65. OSHA specifies a NA range of 0.65 to 0.75. With

an objective having NA = 0.65, and at a total system magnification of 500x, the smallest diameter of a suspected

fiber which could be seen was approximately 0.4 ym. Hence,

any fiber 5 ym long but having a diameter less than 0.4 ym,

could never be found unambiguously. The class of particles

defined as fibers and visible by the procedure is depicted

as the cross hatched portion shown in figure 2.

Note: The OSHA-SLC laboratory , in addition

to phase-contrast microscopy > sometimes uses

polarized light microscopy with a retardation

plate to distinguish asbestos fibers from

talc plates oriented on end and from other

non-asbestos fibers such as glass or organic

fibers which may have been present in the

samples. Since these techniques are not part

of the phase-contrast method they were not

used at NBS.

NBS used two analysts working independently and

following the procedure given above in obtaining the results

on the OSHA-supplied talc samples. While the analysts did

not have, prior to this study, an extended period of experience with the specific methodology employed, they have had

extensive experience in a wide range of particle characterization techniques, including general optical microscopy.

11
III. Preliminary -Investigations of Samples

A. Macroscopic Description of Samples

A qualitative description of the 80 samples supplied

to NBS by OSHA is given in table 1. The sample numbers are

those assigned by OSHA. The number after the description

refers to the number of the color chip in the Inter-Society

Color Council-NBS Color Name Chart (Supplement to NBS

Circular 553)

.

B. Scanning of Samples

Specimens of the 80 talc samples were mounted on

slides "by each analyst independently, using the "dip" method

described in Section II. 2 above. These specimens, each

containing %1000 particles, were then scanned rapidly,

i.e . , only the presence or absence of fibers was noted and

fiber counts were not made at this time. As a result of

tiiese scans, specimens taken from 31 samples were identified

by both analysts as containing at least one fiber, specimens

taken from an additional 21 samples were identified as

containing at least one fiber by one analyst but no fiber

was seen by the other analyst, and no fiber was seen by

either analyst for specimens taken from the remaining 28

samples

.

IV. Counting and Analysis of Samples

A. Samples Noted by Both Analysts as Containing Fibers

As noted above, 31 samples were identified by both

analysts as containing fibers during scanning. Data for

these samples are given in table 2. The observed counts for

each specimen by each of the two analysts, listed as F/ (P+F)

(i.e. 3 fibers divided by non-fibrous particles + fibers) are

shown. In addition the estimated percent of fibers (p) , and

the lower (L) and upper (U) limits of a 95 percent confidence

interval for the "true" value of p for the slide on which the

12
count was made are given.* It should be noted that the

confidence interval refers only to the portion of fibers on

the slide on which the count was made, and not necessarily

to the true average of fibers in the entire sample. (Estimations of the latter would require that the slide constitute a random sample of a homogeneous material under examination.)

It is seen that for eight of these 31 materials,

the confidence intervals for replicate slides failed to

overlap, indicating a lack of statistical compatibility

between these replicate determinations. To study in more

detail the consistency (or lack thereof) of the results from

replicate slides, a more exact statistical analysis was

performed by considering the actual fiber and particle

counts for each material as the elements of a contingency

* The calculation of confidence limits, and other statiscal analyses in this report, are valid under the

assumptions (i) that the fibers are randomly located

among the particles on a slide, and (ii) that the

stopping rule of Section 11.4(8) above introduces

negligible bias.

The confidence interval is based on the relation:

Prob [at most c occurrences of event E in N trials]

Prob

[

F 1 i?f]

where P is the probability of an event E, F is the F

statistic with n^ and n

2 degrees of freedom, and

n-^ = 2(c + l)

n

2 = 2 (N-c)

This relation is cited in Fisher, R. A., and Yates, F.

,

Statistical Tables , Hafner Publishing Company, N. Y.

(1963) p. 3.

13
table* and calculating the corresponding chi-square value*.

A significant value for chi-square, at the 5 percent level

of significance, was taken to indicate statistical incompatibility between the replicate slides. The samples for which

significance at the 5 percent level was thus determined are

identified by an asterisk in table 2. Of the 31 materials,

17 showed incompatibility between replicate slides at the

5 percent level of significance.

The fact that over 50 percent of the results of

these 31 samples were incompatible suggests problems either

of inhomogeneity, or of difficulty in the determination of

fiber morphology, or both. If the sample is inhomogeneous,

the reason for the statistical incompatibility is obvious.

The problem of determining fiber or particle morphology is

very difficult as there is often a great deal of subjectivity

in deciding whether or not a particle meets the criteria to

be classed as a fiber. Photomicrographic examples of

(1) a specimen containing unambiguous fibers, (2) a specimen

in which no fiber can be discerned, and (3) a specimen which

required a great deal of judgment are shown in figure 3, a,

b, and c respectively. In figure 3 six different fields of

view are shown for each specimen, three using an optical

microscope and three using a scanning electron microscope

(SEM) . (The SEM fields do not correspond to the optical

fields, but were chosen randomly.)

In the case of talc samples, one must also judge

which of the apparent fibers are talc platelets seen on

edge. It is possible to "roll over" some of these platelets

by moving the cover plate slightly, but while doing so, one

also may "roll" another platelet into a position where it

would subsequently be viewed from the edge.

* Snedecor, G. W. , and Cochran, W. G., Statistical Methods , 6th Ed., The Iowa State University Press, Ames, Iowa

(1967) . Eqn . 8.10.3, p. 217.

14
B. Samples Noted Initially by Both Analysts as not

Containing Fibers

Because of our concern over the incompatibility

of results in the 31 samples in which both analysts agreed

there were fibers, we decided to reexamine a portion of the

group of 28 samples originally classed by both analysts as

not containing fibers. Ten samples were selected at random

from the pool of 28 samples and were scanned a second time.

(Before discussing the results of additional scanning

and counting in this group of samples, it is useful to calculate

the probability of seeing no fibers in a count of N objects

(particles or fibers). The probability is a function of the

true fiber content of the material from which the slide is

prepared. The calculation is based on the assumption that

the specimen ( i.e the portion of the material on the

slide) is a random sample from the material being measured.

According to the binominal distribution,* the probability

(zero fibers in count of N) equals (1-P) where P=^jq,

and p is the number percent fiber content of the material.

Table 3 lists values of this probability for various values

of p, for N=200, 500, 1000, and 2000. It is evident that

the probability of seeing no fibers in two slides of 1000

counts each (N=2000) is extremely small unless the true

fiber content of the material is less than 0.25 percent.

(Even for N=200, the probability of seeing no fibers is very

small unless the fiber content of the material is less than

2.5 percent). One would therefore expect the materials in

this group to have fiber contents not greater than 0.25

percent

.

It is also interesting to note that for materials with

very low fiber content, say 0.01 percent, there is only an

18 percent probability of finding at least one fiber in a count of 2000. In order to reach a probability of 95

* Ibid . , Chapter 8.

15
percent of finding at least one fiber in such a material,

one would have to examine at least 30,000 particles. For a material with a 0.1 percent fiber content, the number of

particles required to find at least one fiber with 95 percent

probability is 3000.)

As a result of the second scan on newly prepared

slides, four samples were still identified as fiber-free,

but fibers were observed in the remaining six samples. The

results are given in table 4.

Four samples showed fiber contents larger than

0.25 percent by both analysts. Furthermore, for two of

these samples, the two new slides gave incompatible results

(as shown by the chi-square test). These are indicated by

an asterisk in table 4.

The results obtained from this reexamination of

the materials in the group of initial negative scans thus

support the interpretations given by the analysis of the

samples in the first group: inhomogeneity and/or

subjectivity in deciding fiber morphology.

C. Samples Noted as Containing Fibers by Only one

Analyst During the Initial Scan

The remaining pool of 21 samples, which were noted

as containing fibers by only one of the analysts during the

initial scan, was then examined. In all of these cases the

percent of fibers was estimated to be low and the arguments

given above about the probability of finding fibers as a function of total number of particles are equally valid. In

this case, eight samples were selected for fiber counts.

Of the eight samples selected, seven provided incompatible

replicates, given further support to the interpretation made

on the basis of the other two groups of samples. These

data are given in table 5. Again, incompatible results are

indicated with an asterix.

16
V. Conclusions

In this report the results of the determination of the

fiber content of 80 OSHA- supplied samples of talc are

presented, along with a statistical interpretation of these

results. Of the 45 samples on which fiber counts were made,

the results for replicate analyses on 26 of the samples were

statistically incompatible. This incompatibility was not

confined to any particular concentration range of fibers.

As a result, NBS deemed it inadvisable to report uncertainty

limits for the fiber content determinations obtained on the

samples measured. Fiber counts could be made using the

present procedure on the 35 samples which were not counted,

but it is doubtful that any useful additional information

would be obtained.

The variability of these results raises several questions

regarding the OSHA procedure, particularly sampling technique,

sample homogeneity, and determining fiber morphology. It is

the opinion at NBS that, even under favorable circumstances

(e . g . _, homogeneous samples, easily identified fibers, etc.),

the existing OSHA procedure is useful only for determining

"fiber" content and not "asbestos" content. Although careful

manipulation of the mounting medium might make it possible

to identify some of the fibers as "asbestos", the problem of

the definition of "asbestos" still remains. NBS believes

that the resolution of the measurement problem, including

the definition and identification of asbestos, will be

accomplished only by significant changes in the procedure

and probably the method as well.

In order to complete the tasks requested by Dr. Corn in

his letter of September 1, 1976, it will be necessary to

arrive at an acceptable definition of asbestos and to

develop the necessary measurement techniques and standards.

Once that has been achieved, a more meaningful analysis of

the 80 OSHA- supplied talc samples can be accomplished.

17
Table 1

Description of bulk material

Sample

1

2

3

4

5

6

7

34

35

36

37

38

39

Description

fine white powder (263)

fine white powder (263)

fine white powder (263)

fine white powder (263)

fine white powder (263)

fine white powder (263)

fine white powder (263)

fine white powder (263)

coarse ' grains (sand-like) (92)

inhomogeneous

fine off-white powder (93)

beige fine-grained nonhomogeneous

some dark material, some light (93)

beige fine-grained nonhomogeneous

some dark material, some light

material (93)

off-white powder (92)

40 fine

41 fine

42 fine

very light grey powder (92)

light grey powder (264)

white powder (263)

43 fine white powder (263)

44 fine white powder (263)

18
Table 1 (continued)

Sample

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

Description

fine white powder (263)

fine white powder (263)

fine white powder (263)

light brown powder (264)

off-white powder clumps together

in small aggregates (263)

off-white powder clumps together

in small aggregates (263)

light grey powder (154)

grey granular material, nonhomogeneous C155)

light grey powder (fine) (154)

fine white powder (263)

fine off-white powder (92)

grey granular material, nonhomogeneous (154)

fine white powder, some

aggregation (263)

fine off-white powder (263)

off-white powder clumps together

in small aggregates (92)

off-white powder clumps together

in small aggregates (263)

dark grey granular, some small

fragments (265)

fine off-white powder (263)

fine off-white powder (9)

19
Table 1 (continued)

Sample

64

65

66

67

68

69

70

71

72

73

74

75

76

78

79

80

81

82

Description

fine brown-grey powder (264)

fine grey powder (265)

fine off-white powder (264)

off-white powder, some

aggregation (263)

fine white powder (263)

off-white powder, some aggregation (263)

fine off-white powder (92)

off-white powder, some

aggregation (263)

off-white powder, some

aggregation (92)

small light grey pebbles and

powder, inhomogeneous (264)

fine light grey powder (264)

fine off-white powder (264)

fine grey powder (154)

light grey to brown powder (264)

dark grey rock, some large

fragments but mostly small

grains (265)

fine grey powder (264)

off-white powder (fine) (9)

dark grey rock, mostly large

fragments with some granular

material (265)

20
83

84

86

87

88

89

91

92

93

94

95

96

97

98

99

100

101

Table 1 (continued)

Description

•dark grey rock, mostly large

fragments with some granular

and powdered material (265)

dark grey rock almost all large

fragments, very little granular

or powdered material (266)

dark grey granular material with

some large fragments (265)

white and pink rocks, very little

granular or powdered material (9)

coarse granular light brown

several large fragments with

some powder (93)

grey-brown granular, inhomogeneous (93)

fine off-white powder (263)

white rock with powder (263)

grey and brown rocks (93)

fine white powder (263)

off-white powder, some aggregation (263)

fine white powder (263)

fine white powder (263)

fine off-white powder (92)

fine beige powder (153)

fine white powder (263)

white to light grey rocks with

a fairly large amount of

powder (92)

21
Table 1 (continued)

Sample

102

103

104

105

106

107

108

109

Description

large grey rocks with white

powder 0 the bottom (153)

fine white powder (263)

off-white powder (263)

fine white powder (263)

fine white powder (263)

large grey and light brown

rocks, some powder in the

bottom, very inhomogeneous (92)

fine white powder (263)

white powder, extensive

aggregation (263)

22
Table 2

Results of the 31 Samples Identified as Containing Fibers

by Both Analysts on the Initial Scan

Analyst 1 Analyst 2

951 Confidence

Intervals

95% Confidence

Intervals

Sample

No.

Count

[E/CP+F)]

Pm

L

m

U

m

Count

[F/CP+F5

]

Pm

L

m

U

(%)

1 102/760 13.4 n.i 16.0 125/833 15.0 12.7 17.6

2* 135/809 16.7 14.2 19.4 142/1138 12.5 10.6 14.5

3 100/480 20.8 17.3 24.7 103/445 23.1 19.3 27.3

4 105/660 15.9 13.2 18.9 109/670 16.3 13.6 19.3

5 100/711 14.1 11.6 16.8 109/720 15.1 12.6 18.0

6 158/1606 9.8 8.4 11.4 83/714 11.6 9.4 14.2

7* 102/852 12.0 9.9 14.3 102/586 17.4 14.4 20.7

34* 101/696 14.5 12.0 17.3 105/1028 10.2 8.4 12.2

38* 45/652 6.9 5.1 9.1 17/451 3.8 2.2 6.0

41* 100/991 10.1 8.3 12.1 70/501 14.0 11.1 17.3

42 105/593 17.7 14.7 21.0 106/492 21.5 18.0 25.4

43 103/885 11.6 9.6 13.9 102/829 12 .

3

10 .

2

14.7

45 106/682 15.5 12.9 18.5 86/627 13.7 11 .

1

16.6

46 104/1163 8.9 7.3 10.7 103/1155 8.9 7 .

3

10.7

47 104/543 19.2 15.9 22.7 136/817 16.6 14.2 19.4

49* 142/1263 11 . 2 9.6 13.1 102/393 26.0 21.7 30.6

50* 124/659

100/848

18.8

11.8

15.9

9.7

22.0

14.2

127/600

76/866

21.2

8.8

18.0

7.0

24.6

10.9

* Incompatible replicates.

23
Table 2 (continued)

Analyst 1 Analyst 2

95% Confidence

Intervals

95% Confidence

Intervals

Sample

No

.

Count

[F/ (P + F)

]

Pm

L

m

U

(%)

Count

[F/ (P+F)

]

Pm

L

m

UW

52* 100/919 10.9 8.9 13.1 54/767 7.0 5.3 9.1

56 72/900 8.0 6.3 10.0 54/581 9.3 7.1 11.9

58* 48/1863 2.6 1.9 3.4 29/503 5.8 3.9 8.2

60* 100/1285 7.8 6.4 9.4 60/1190 5.0 3.9 6.4

68 67/1901 3.5 2.7 4.4 79/1685 4.7 3.7 5.8

87/2237 3.9 3.1 4.8

75* 111/1474 7.5 6.2 9.0 109/686 15.9 * 13.2 18.8

105/1245 8.4 7.0 10.1

76* 100/759 13.2 10.8 15.8 100/522 19.2 15.9 22.8

87 48/471 10.2 7.6 i3 .$ 55/527 10.4 8.0 13.4

92 101/329 30.7 25.8 36.

0

111/314 35.4 30.1 40.9

94* 35/3276 1.1 0.7 1.5 105/906 11.6 9.6 13.8

72/1674 4.3 • 3.4 5.4

95* 43/1947 2.2 1.6 3.0 37/2820 1.3 0.9 1.8

96* 55/1571 3.5 2.6 4.5 36/625 5.8 •4.1 7.9

104* 69/959 7.2 5.6 9.0 101/773 13.1 10.8 15.6

109* 111/2674 4.2 3.4 5.0 104/1890 5.5 4.5 6.6

* Incompatible replicates.

NOTE: Confidence limits were calculated using an approximate

formula and a few may be in error by one or two units

in the last place.

24
Table 3

Probability of Finding No Fibers in Counts of Size N

True Fiber Size of Count

Content

,

in Percent N=200 N=500 N=1 000 N=2000

0.01 0.98 0.95 0.90 0.82

0.05 0.90 0.78 0.61 0.37

0.10 0.82 0.61 0.37 0.14

0.15 0.74 0.47 0.22 0.05

0.20 0.67 0.37 0.14 0.02

0.25 0.60 0.29 0.08 0.01

0.30 0.55 0.22 0.05 <0.01

0.40 0.45 0.13 0.02

0.50 0.37 0.08 0.01

0.60 0.30 0.05 <0.01

0.80 0.20 0.02

1.00 0.13 0.01

1.50 0.05 <0.01

2.00 0.02

2.50 <0.01

25
Table 4

Results of the 28 Samples Identified by Both Analysts as

Not Containing Fibers on the Initial Scan

Analyst 1 Analyst 2

95% Confidence

Intervals

95% Confidence

Intervals

Sample Count p L U Count P L u

No. [F/(P+F) ] C%) (%) m [F/(P+F)] w (*) m

36 not counted

37 not counted

1 54* 22/828 2.7 1.7 4.0 5/899 0.6 0.2 1.3

55 not counted

61 not counted

+ 62 4/1395 0.3 0.1 0.7 0/1410 0.0 0.0 0.2

+ 63 no fibers observed on second scan

+ 65 no fibers observed on second scan

+ 66 18/1545 1.2 0.7 1.8 10/1598 0.6 0.3 1.1

.70 not counted

71 not counted

72 not counted

73 not counted

78 not counted

80 not counted

81 not counted

* Incompatible replicates,

t Samples selected for second scan.

26
Table '4 (continued)

Analyst 1 Analyst 2

951 Confidence

Intervals

95% Confidence

Intervals

Sample

No.

Count

[ F / (P+F)

]

£X,©\° V

/

L

m

U

m

Count

[F/ (P+F)

]

Pm

L

m

U

m

+82 no fibers observed on second scan

84 not counted

86 not counted

+ 88 no fibers observed on second scan

89 not counted

91 not counted

93 not counted

+ 98 18/746 2.4 1.4 3.8 9/522 1.7 0.8 3.2

+ 101 2/200 1.0 0.1 3.6 6/230 2.6 1.0 5.6

102 not counted

107 not counted

+ 108* 56/833 6.7 5.1 8.6 18/1165 1.5 0.9 2.4

* Incompatible replicates,

t Samples selected for second scan.

27
Table 5

Results on the 21 Samples Identified as Containing Fibers

by Only One Analyst on the Initial Scan

Analyst 1 Analyst 2

95% Confidence 95% Confidence

Intervals Intervals

Sample Count p L U Count P L U

No. [F/CP-F)] (%) (%) m [F/ (P+F)

]

m m m

35 not counted

39 29/813 3.6 2.4 5.1 9/550 1.6 0.7 3.1

40 not counted

44* 100/905 11.0 9.1 13.3 81/418 19.4 15.7 23.5

48 not counted

51* 45/833 5.4 4.0 7.2 39/1354 2.9 2.0 3.9

53* 50/1091 4.6 3.4 6.0 42/1771 2.4 1.7 3.2

57 not counted

59 not counted

64 not counted

67 not counted

69 not counted

74 not counted

79 not counted

83* 18/430 4.2 2.5 6.5 3/630 0.5 0.1 1.4

97* 36/1861 1.9 1.4 2.7 18/1693 1.1 0.6 1 . 7 99* 30/1212 2.5 1.7 3.5 1/739 0.1 0.0 0.8

* Incompatible replicates.

28
Table 5 (continued)

Analyst 1 Analyst 2

951 Confidence

Intervals

95% Confidence

Intervals

Sample

No.

Count p

[f/ (p + f) ] m

L

m

U

m

Count

[ F/ (P+F)

]

Pm

L

m

u'

m

100 not counted

103 not counted

105* 86/1498 5.7 4.6 7.0 27/777 3.5 2.3 5.0

106 not counted

* Incompatible replicates.

29
N=1 23456 7 8 9

Figure 1. Porton Reticle
30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

MAXIMUM LENGTH

NOT SPECIFIED

RESOLUTION LIMIT OF MICROSCOPE

0.4 |im

I 1 I I I I

1 2 3 4 5 6

PARTICLE WIDTH, /jm

Fiber dimensions that would be observed as per OSHA

definitions and resolution limit of microscope.

31

Sample

Light Microscope

92

Scanning Electron Microscope

Figure 3a
,
Sample 81

Light Microscope Scanning Electron Microscope

Figure 3b

'SiJ

Sample 108

Light Microscope Scanning Electron Microscope

9 Figure 3c

APPENDIX I

U.S. DEPARTMENT OF LABOR

Occupational Safety and Health Administration

WASHINGTON, D.C. 20210

Office of the Assistant Secretary

September 1, 1976

Dr. John Dehoffman

National Bureau of Standards

Building 223, Room B-368

Washington, D. C. 2023h

Dear Dr. Dehoffman:

The purpose of this letter is to confirm the request for analysis

of talc samples, as discussed by you and Dr. B. K. Kwon of OSHA.

We ask that you determine the asbestos content of these samples.

The analysis of talc samples for asbestos is performed by OSHA and

NIOSH, but the methodology is being challenged by those regulated

by OSHA.. Thus, I request that you investigate the asbestos content

of these samples independently of OSHA, NIOSH, MESA, the Bureau of

Mines or the private sector.

In a real sense, we look to you to resolve, (l) the variability in

the definition of asbestos fibers in talc and (2) the asbestos

content of these samples, expressed as number of fibers per unit

weight or unit volume. Also, the asbestos content as percent of

total weight, per the definition in (l) above, would be useful.

We recognize it will be necessary to estimate these parameter from

a sample of the materials forwarded to you.

Copies of the OSHA standards on asbestos, the proposed revised

asbestos standard and two relevant articles are enclosed. Also,

I request that you maintain close contact with Dr. B. K. Kwon of

OSHA. As we previously discussed, this is an urgent matter and we hope the work can be completed as soon as possible.

1-1
2

Your assistance in resolving this difficult and lingering controversial

issue is greatly appreciated. It is our desire to continue to maintain a good working relationship between our two agencies.

Sincerely yours,

f//eZ

MORTON CORN

Assistant Secretary of Labor

Enclosures
2 3 SEP 1976

o* +

s UNITED STATES DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington. D.C. 20234

Dr. Morton Corn

Assistant Secretary of Labor

Occupational Safety and

Health Administration

U. S. Department of Labor

Washington, D. C. 20210

Dear Dr. Corn:

I am writing in response to your letter of September 1, 1976,

in which you requested that the National Bureau of Standards

perform two tasks:

(1) resolve the variability in the definition of

asbestos fibers in talc, and

(2) determine the asbestos content of a series

of talc specimens.

We have briefly investigated in a general way the complex

problems and arguments associated with the detection and

measurement of asbestos. Although we are not currently

performing asbestos analyses, we have several staff members

who are experts in the chemical and physical characterization

of particulates and who are informed on the talc fiber

question as a result of discussions with people from federal

agencies and private industry. We have based this reply on

their knowledge and the literature available on measurement

techniques for asbestos type materials.

NBS is quite often called upon by federal agencies to resolve

questions in measurement methods and standards. It is always

our practice to discuss these problems with all available

experts in federal laboratories, regulatory agencies, private

industry and universities to develop an understanding of the

current practices, points of controversy and specific

measurement problems. The conclusions reached in these

studies are developed independently and are a result of NBS

technical expertise and judgement. If this type of operation

is acceptable to you, we would be willing to participate in

a program to develop definition methods and standards for

asbestos analysis, which may lead to the resolution of the

variability in the definition of asbestos and the question

concerning the fiber in talc.

1-3
2Your first question, resolving the varibility in the

definition of asbestos fibers, seems to involve a large

program that requires the identification of the important

variables of the definition as they relate to health effects

and then the development of methods to measure these

variables effectively. Questions which involve health effects

are outside the mission and competence of NBS and in our view,

may not be resolvable through chemical and physical analysis

alone. However, as a component of a larger program, NBS could

compare the OSHA Federal Register methods of analysis with

other proposed methods, such as scanning electron microscopy,

electron probe microanalysis, selected- area electron

diffraction, x-ray diffraction or differential thermal analyses.

It is our opinion that this project would make a significant

contribution to answering your first question but would have

to be performed in cooperation with other federal agencies

involved in the development of the important health effect

variables. As an output of this project, NBS would probably

develop Reference Methods of Analysis and Standard Reference

Materials for asbestos. We would estimate that the NBS

component of this project would require approximately three

man years and cost $225,000.

In response to your second request, the determinations of the

asbestos, content of talc samples, we would be in a position

to perform this analysis duplicating the methods used by OSHA,

NIOSH and MESA as specified in the Federal Register (29 CFR

Part 1910) . Assuming that there would be 80 samples involved,

we estimate' that this analysis, which would be billed on a reimbursable basis, would require no more than four man

months and not exceed $25,000. Since this analysis would be

based on the definition of asbestos as specified in the

Federal Register, it is unlikely that this project would

serve to answer your first question. Furthermore, our initial

investigation has indicated that there does not appear to

be an agreement in the scientific community as to whether

a specific fiber of a particular chemical composition is

asbestos or not. For example, neither Dana's Manual of

Mineralogy (18th ed.) nor Deer et al.'s Rockforming Minerals

give a concise definition of either a fiber , or of asbestos

per se . Deer et al. say (Vol. 2, p. 223): "The habits of the

anthophyllite mineral vary. from fibrous and asbestiform to

bladed and prismatic". Any number of similar descriptions

can be found in the literature.

1-4
3

If you would like us to perform the analysis of the talc

samples or if you choose to establish a larger inter-agency

program involved in defining asbestos variables, I suggest

that members of your staff contact Dr. C. C. Gravatt, Deputy

Chief, Analytical Chemistry Division, 921-2852, to work out

the details of our involvement. If I can be of any further

assistance in this matter, please let me know.

Sincerely,

Original « ,, .f'tr

John D. Hoffman

Director

Institute for Materials Research

be: Signer

Dr. E. Ambler

E. Horowitz

G. Sinnott

B. Morrissey

J. Wachtman

R. Hayes

P. D. LaFleur

C. C. Gravatt

I. R. Barkty

K. F. J. Heinrich

J. Taylor

A. Farrar

310 : 00 : CCGravatt : gbh 9-21-76

Retyped

310 . 00 : CCGravatt : gbh 9-23-76

1-5
U S. DEPARTMENT OF LABOR

Occupational Safety and Health Administration

WASHINGTON, D.C. 20210

Office of the Assistant Secretary

8 OCT 1976

Dr. John D. Hoffman

Di rector

Institute for Materials Research

National Bureau of Standards

U.S. Department of Commerce

Washington, D.C. 20234

Dear Dr. Hoffman:

I am writing in reply to your letter of September 23, 1976, in which

you presented an approach by the National Bureau of Standards to the

performance of two tasks which I previously requested in my letter of

September 1, 1976. The tasks are as follows:

(1) resolve the variability in the definition of asbestos

fibers in talc, and

(2) determine the asbestos content of a series of talc specimens.

I am in total agreement with your statement that the first task encompasses efforts by others than staff of the National Bureau of Standards

in order to resolve current uncertainties in the definition of asbestos

fibers in talc. It is also clear that for a most meaningful resolution

of this question the properties of fibers in talc as they relate to

epidemiological studies in the talc industry should be examined. I fear

that the formulation of the study plan to approach this task will require

a period of time of at least six months. However, I agree with you that

this long range project would have a great deal of meaning for the assess- ment of both the occupational and environmental exposures of individuals

to asbestos fibers. Therefore I would like to approach with you the

establishment of a study to address Task One.

The second task also requires resolution and I was pleased to learn that

the Bureau can undertake this during a period of time represented by

approximately four-man months of effort at a cost of $25,000. This is

recognized to not be a research task. However, current disagreements

in the occupational health field concerning the results of analyses

performed according to procedures in the Federal Register (29 CFR Part

1910) are causing great difficulties to those of us concerned with

implementation of the Occupational Safety and Health Act of 1970. Therefore, analyses by your laboratory of approximately 80 samples would

1-6
2

enable us to proceed with enforcement on the basis of the current methodology. Even after conclusion of your analyses there are those who

may challenge the current methodology, but we will be in a better

position to provide relief to those being exposed to asbestos if there

is at least consistency of analysis with respect to current recommended

analytical methodology. Therefore, please consider this letter an agreement on my part to proceed with Task Two.

For purposes of discussing both Task One developmental efforts and Task

Two procedures, I request that you remain in communication with Dr.

Byung Kwon of this agency, who will act as the project officer for both

endeavors.

I wish to thank you for your prompt and encouraging response to the

needs of the Occupational Safety and Health Administration on this

occasion. I hope that we can continue to work with you in the future.

Sincerely,

Morton Corn

Assistant Secretary of Labor

1-7
3 NOV 1976

*^ru o*

UNITED STATES DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, D.C. 20234

Dr. Morton Corn

Assistant Secretary of Labor

Occupational Safety and

Health Administration

U. S. Department of Labor

Washington, D. C. 20210

Dear Dr. Corn:

I am writing in reply to your letter of October 8, 1976.

The National Bureau of Standards is pleased to be able to

participate in both of the following tasks as described

in your letter:

(1) resolve the variability in the definition

of asbestos fibers iit talc, and

(2) determine the asbestos content of a series

of talc specimens.

With respect to task number 1, Dr. C. C. Gravatt, Deputy

Chief, Analytical Chemistry Division, will work with

Dr. Byung Kwon of your staff to plan the NBS component

of this interagency program. It is my understanding that

they will be meeting in the near future, possibly with

representatives of other Federal agencies to begin the

development of this program.

The samples to be analyzed by NBS for the second task were

picked up from Dr. Kwon by Dr. Gravatt on October 29.

The samples were contained in a sealed package sent to

Dr. Kwon by NIOSH and were thought to be blind samples

i.e., the identification of the source of each sample was

not to be in the package. When Dr. Gravatt opened the

package on November 1, he found 80 samples indicated by

the numbers on the attached sheet but also a document

which identified the source of these 80 samples. Dr.

Gravatt is the only person at the National Bureau of

Standards who had read the document and after checking

the sample numbers against the list, the document was

placed in a security safe at the National Bureau of

Standards. We will not read the document again and

will await your recommendations as to its deposition.

1-8
2

Dr. Gravatt informed a Mr. Darrell Mathas of Dr. Kwon '

s

Office of the existence of this document. We will initiate

analysis of these 80 samples in the near future and expect

to complete the work on or before March 1, 1977. We will

be in contact with Floyd Matson and Willard Dixon of your

Salt Lake City Laboratory concerning the specific

procedure to be followed in this analysis. It is our

understanding that Dr. Kwon will be forwarding a purchase

order to us in the near future to cover the cost of

this analysis.

We are glad to be of assistance in both of these projects.

Sincerely

,

Ori^ir.-n

b

° U

' "< i-. John D. Hoffman

Director

Institute for Materials Research

be: Signer

Dr. E. Ambler

E. Horowitz

A. Farrar

G. Sinnott

B. Morrissey

310:00: CCGravatt : ghb 11-1-76

v

1-9
Samples Received by NBS from OSHA

October 29, 1976

001

002

003

004

005

006 cap open § some loss

of material

007

034

035

036

037

038

039

040

041

042

043

044

045

046

047

048

049

050

051

052

082

083

084

086

087

088

089

091

092

093

094

095

096

097

098

099

100

101

102

103

104

105

106

107

108

109

053

054

055

056

057

058

059

060

061

062

063

064

065

066

067

068

069

070

071

072

073

074

075

076

078

079

080

081

1-10
APPENDIX II

The following set of notes were taken during a meeting with Mr. Willard

C. Dixon of the OSHA Analytical Laboratory, 390 Wakara Way, Salt Lake

City, Utah.

Willard Dixon (WD) is in charge of the microscopic analysis of

samples for "asbestos" fiber content. As a result of a recent contract

NBS has been requested to analyze several samples for "asbestos fibers"

according to the procedures used at the OSHA laboratory. The purpose of

the visit to Salt Lake City was to obtain information on their methods

of microscopic analysis.

Meeting Date: 12/13/76

Sample Preparation

The preparation of bulk talc samples by the OSHA labs in Salt Lake

City is done by the following procedure: Two drops of a mounting

medium are placed on a clean microscope slide. Next, the end of a paper

clip is dipped first into the two drops of solution and then into the

bulk sample. The amount of material sticking to the end of the paper

clip is mixed with the mounting solution on the slide. Finally, a cover

slip is placed over the top of the preparation. The OSHA labs assumed

that the talc samples were homogeneous when received. They do, however,

draw two "representative" samples from different areas of each bulk talc

sample

.

Fiber Counting

The fiber counts on the different samples were done according to

the procedure outlined in the draft of the article "Asbestos Fibers in

Air" which was sent to us by WD on November h, 1976. | In addition,

after November 21, 197^ they also used the revisions as proposed in the

Department of Labor field information memorandum #7^-92 dated November

21, 197^ » when analyzing asbestos in talc. | liiis memorandum, among

other things, suggests an aspect ratio of five to one rather than three

to one as the definition of a fiber. WD commented that the change to

the larger aspect ratio did not have a major influence over the results,

for tremolite asbestos in Vanderbilt Nytall Talc.

The "bundle of sticks” criterion mentioned in the memorandum is not

strictly implemented because of the ambiguous nature of the statement.

The OSHA labs move the slide coverslip when necessary to determine

if a given particle is a fiber or a talc plate standing on end.

1

1

-

1
Analytical Procedure

WD considers light microscopy tests to be of qualitative value

only . Quantitative analysis of a mineral vould be done by x-ray diffraction J if the results of light microscopy testing are not sufficiently ~Vonclusive

. j ~

The OSHA labs followed two different analytical procedures for the

analysis of talc samples by light microscopy.

The first method was used prior to June 2, 1976. (On or about

June 2, 1976 the OSHA labs were visited by a representative of the

Vanderbilt Talc Co.)| The first method used phase contrast microscopy.

The mounting solution was a Cargi lle liquid with a refractive index of

1.5^6; {l . 47 media was also used.l The index of 1.5^6 was used because

this is the index where quartz and

j

chrysotile asbestos dispersion stains)

[blue in bright field using a Zleiss phase contrast microscope.^ All

fibers in the samples were counted according to the procedure outline

in the article "Asbestos Fibers in Air," [except as modified by memorandum #7^-92 for asbestos in talc. When the sample is not on a membrane, this will require modification of the procedure. The procedure

doesn't specify the use of auxiliary methods of examination such as polarized light, or retardation plates, however WD will use any auxiliary method he finds helpful in asbestos identification. The study of

polarized light color patterns with a first order red retardation plate

and crossed polars was an important technique in fiber identification

before June 2, 1976.

The second method of sample analysis which was used after June 2,

1976 was dark field dispersion staining. The dark-field effect was produced by mismatching the phase contrast objective and the stop on the

annulus in the condenser. The samples were mounted in a Cargille high

dispersion liquid with a refractive index of 1.600. The results were

reported as two separate fiber counts based on the dispersion staining

color. One count reported the fibers which dispersion stained orange.

These fibers were considered to be Itremolitef asbestos. The second count

reported fibers which dispersion stained blue. These fibers were not

considered to be asbestos.

After careful study of fiber characteristics, morphology, and

colors in both bright field and dark field the fibers were counted in

bright field at ^00 X. If a fiber could not be identified in bright

field the counted switched to dark field for identification then back to

bright field to continue counting.

According to WD, there is a question concerning the validity of

reporting the fibers which dispersion stain blue as not being asbestos.

He said the shift in analytical procedure on June 2, 1976 was induced by

the discussion with technologists from the Vanderbilt Co. At that time,

the Vanderbilt Co. convinced him of the merits ofj l.59 or 1.60 media to

[distinguish between Tremolite asbestos and talc fibers.

1

- 2
WD had learned about Dispersion staining from Walter C. McCrone associates

literature and then began us ing dispersion staining to assist in diffentiation using 1.60 media.

{

Just recently, however, WD has received a sample from the California Department of Health which is called "White

Tremolite." This material, which is fibrous, dark field dispersion

stains blue in a liquid with refractive index of 1.600. If this material

is in fact tremolite, then the fiber counts done by dispersion staining

would under estimate the tremolite asbestos fiber content of the samples.

The OSHA lab is currently studying the "White tremolite to determine if

it is in fact tremolite. WD has given us a sample of the material

which we are now studying using micro-Raman and x-ray micro-analysis.

The sample of tremolite along with a second sample called "purple tremolite" were obtained by the California Department of Health from

Wards Natural Science Establishment, Inc.

P.0. Box 1712

Rochester, New York 14603

phone 716/467-8400

Other Procedures

Routinely the samples of talc are also analyzed by polarized light

microscopy. This procedure would separate materials such as fiber

glass from asbestos and with a first order red retardation plate helps

to identify talc, asbestos fiber, plant and other fibers by the pattern

of colors produced and the color changes with rotation of the stage.

Miscellaneous Information

Mounting Liquids:

WD commented that the liquids made by Cargille with refractive

indices less than 1.4 may deteriorate, but the liquids with refractive

index above this value are very stable.

Sample Grinding:

The OSHA lab assumes that the talc samples sent to them are representative of the bulk product or of airborne talc dust. The material

is not further ground in the lab since in further grinding the fiber

count would change.

Mounting Liquid:

WD said that if the talc samples were mounted in the mounting

solution (see membrane filter method mentioned in the article "Asbestos

Fiber in Air"), which has a refractive index of approximately 1.47,

then it would not be possible to tell asbestos from talc in the dispersion staining method.

1 1 - 3
Filter Standards

The filter samples sent to us by WD were the NIOSH Proficiency

Analytical testing samples (PAT). These samples are used for interlaboratory checks on counting. The fibers on these samples are ex- tremely fine chrysotile fibers and are considerably more difficult to

count than the fibers in the talc samples.

Problems with Inexperienced Counters

WD said there are two problems with new counters

1. They may not use the fine focus enough to detect fine fibers.

2. They may count membrane filter structure as fibers.

The second problem applies specifically to air samples so that it

will not affect the counts on the talc samples. Dixon commented that

the fibers in the talc samples are fairly large and are easily seen at

Uoox so that the first problem should not be severe.

Asbestos Material in Talc Samples:

The main asbestos material detected in the talc samples was tremolite. fWD has 1 earned since talking to John Small that some of the

fibers he had th ough to be talc fibers in Nytall may be anthophyllite

asbestos fibers.

Mismatching Phase Contract Objective and Annulus:

When the operator mismatches the phase contrast microscope, the

magnification must be recalibrated.

Method of Identifying Wollastonite in the Presence of Amphiboles

The sample is treated with hot concentrated HC1 for 20-30 minutes.

The silicon dissolves leaving a Wollastonite shell behind. This shell

is white and spongy and retains the original shape of the mineral. The

amphiboles are unaffected by the HC1. The Wollastonite can also be

distinguished from the amphiboles by its shape. It has a feathering

appearance on the ends while the amphiboles usually have a prismatic to

right-angle cleavage. | (i.e., 56°, 124° and some cleavage closer to 90),

|but cleavage faces are straight rather than tapering. I

Plant Fibers

Several varieties of vegetal fibers, especially under low magnification, may be identified as asbestos fibers. One way to eliminate

the interference is to ignite the sample. It should be noted that the

sample must not be heated above about 900 °C since chrysotile convert s to

forsterite mg (SiO,

)

a part of the olivine series at approximately

650°C.

^ 4

1 1 - 4
Nytall 99:

The Vanderbilt sample Nytall 99 is believed by WD to be the sample

in contention. The material does contain tremolite which was determined

by x-ray diffraction. This fact has been confirmed by Vanderbilt. The

main question is the identification of the fibers which dispersion-stain

blue, and the definitions of a fiber.

Bulk Standards

WD said that there would be no way to prepare bulk talc samples

doped with asbestos. The only way they could be calibrated was to have

a multi-lab round robin. He has never had any standards for bulk talc

made

.

Sample Size:

WD said that many of the light tests would fail if the fibers are much less than 1 pm in diameter.

"Bundle of Sticks" Effect

For interpretation of the "bundle of sticks" effect, WD usually

used his own judgment. One solution where there may be a problem is in

a sample with a palisading effect, i.e., tremolite (see attached figure).

WD says he would call this a fiber, but Vanderbilt may not. He

says he employs the 3 pm width

(

and 9:1 aspect ratio to determine what

|is a fiber in talc samples.

Interference Samples:

WD showed me several talc samples and materials which can be

confused with either talc or one of the asbestos minerals. These

materials were mounted in both 1.5^6 and 1.600 liquids and studied with

polarized, phase contrast and dispersion staining microscopy. They

included

CaSO^ Talc

Mica Soap stone talc

Wollastonite Nytall

Fiberglass

Plant fibers

Diatomaceous earth

Vermiculite

"Asbestos imitiation"

Natural gypsum

A sample of each of these materials except the talcs was obtained

for study at NBS.

1 1 - 5
PALISADING EFFECT

1

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APPENDIX III

W. C. Dixon

W. J. Campbell,

and staff

M. Ross

B. Mason

E. Jarosewitch

W. Bank

R. Thompson

M. Staunton

W. Banfield

A. N. Rohl

A. M. Langer

J. R. Kramer

C . Ruud

W. McCrone

A. M. Harvey

C. S. Thompson

W. H. Ashton

H. D. Stanley

R. E. Norwood

\ List of Persons Consulted

OSHA Anal. Lab., Salt Lake City, Utah

Particlulate Mineralogy Unit, Bureau of

of Mines, College Park, Maryland

U.S. Geological Survey, Reston, Virginia

Museum of Natural History, Smithsonian

Institution, Washington, D. C.

MESA, Denver, Colorado

EPA, Research Triangle Park, North Carolina

NIH, Bethesda, Maryland

Environmental Sciences Lab., Mt. Sinai

Hospital, School of Medicine, City

University of New York, New York, New York

McMaster University, Hamilton, Ontario

University of Denver, Colorado

McCrone Labs., Chicago, Illinois

R. T. Vanderbilt Co., Inc.

Norwalk, Connecticut

Johnson § Johnson, Baby Products Co.,

Raritan, New Jersey

Pfizer Inc., Minerals, Pigments § Metals

Division, Easton, Pennsylvania

1 1

1

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1
o i

’

'
f’PT’'u7s.*bEPT. OF COMM.

* BIBLIOGRAPHIC data

SHEET

1. PUBLICATION OR REPORT NO. 2. Gov't Accession

No.

3. Recipient’s Accession No.

. TITLE AND SUBTITLE

A Report on the Fiber Content of 80 Industrial Talc Samples

Obtained From, and Using the Procedures of, the

Occupational Safety and Health Administration

5. Publication Date

6. Performing Organization Code

AUTHOR(S) 8. Performing Organ. Report No. Philip D. laFlpur. EriilQrL

PER FORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

2. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Occupational Safety and Health Administration

U.S. Department of Labor

200 Constitution Avenue NW

Washington. D. C. 2Q21Q

13. Type of Report & Period

Covered

14. Sponsoring Agency Code

5. SUPPLEMENTARY NOTES

6. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

The fiber content of 80 talc samples supplied to MBS by the

Occupational Safety and Health Administration of the Department of

Labor have been determined. A statistical analysis of a portion of

the samples has been made.

17. KEY \vORDS (six to twelve entries ; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) I Asbestos; fiber; microscopy; talc

18. AVAILABILITY Uni imited

1 For Official Distribution. Do Not Release to NTIS

1

1 Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SP Cat. No. CU

[

I Order From Nat ional Technical In Springfield, Virginia 22151formation Service (NTIS)

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