Document 1grV85xLGrm33jwJo5ywpn44X
FILE NAME Plastics PLAS
DATE 1975 DOC PLAS002
DOCUMENT DESCRIPTION Journal Article - Handling Asbestos Chrysotile Asbestos in Plastics
%
.
.
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7
Handling Itt ELA a
"
A. ed
g Sade, xe
ChrysotileChrysotile AsbAestossbestos
ON
JOURNAL OF PAINT
TECHNOLOGY an :
tee:
seen .
a
a
|
Ag of
w Laetamewing yt ates tar
tld
Union Carbide Corporation
ARTE eB beter
me tcc teend bee qretleeds ijunafik
Rete
eel
-
esa
|
.
:
molding .
ett,
inibeww
received
feeb
Le
af
a
ren rmee na ede og Fanegy iter FoeW
recent By
taf:
oy oe Daan
APS
Se
oa
orf
Wt
Sy
phenolic
ag bpcs
has a great deal attention Asbers eceit vedos
and publicity in recent years floor tile and in phenolic molding -.
in < especially after it was designated a target health hazard by OSHA and a compounds It is also used other -
hazardous air pollutant by the EPA Many of the articles on asbestos by
the
plastics such as polypropylene
poly- ~
press have been
oriented or distorted and in some cases
.
polypropylene
al
emotionally polypropylene poly- stories have been sensationalized based on obvious misinterpretation facts ester nylon melamine
, epoxy siomly i-
Asbestos The use of truths orunsubstantiated statements has led to general con-
cone and vinyl
provides a
_ fusion and the unfair castigation of asbestos and containing asbestos valuable function in such products as u=ho ~
The purpose of this paper is to put the matter of asbestos use and asbestos ~ i brake linings clutch facings electrical a3=:"
paper the hazards into a logical and practical perspective In this
|
different components automotive furni- *-
types of asbestos and their many uses are discussed along with government ture boats sealants coatings adhe- -
regulations controlling the use asbestos The health hazards associated with ~
| *
of and mastics The asbestos
both
occupational
and
environmental and
some industrial ex-
sives -functions
-functions
most important
asbetos in
.
measures -functions oinfofrcemnt asbestos in plpasltaicssticsstability perience with air sampling and dust control
are also covered
<<<:
KEY
WORDS Asbestos Plastics
wt
Cte
Te -
UY
::
Air pollution Toxicology 5 samen al
" VON LT ST
RP SeL tt. e e Br ee y
-
func
purpose filling Most of the
:
supplied
ar
by
tions are suppbylsihe ordt -
eS
Ge eee
ann
chrysotile asbestos fiber * although What is
longer chrysotile fibers and re- Asbestos is Asbestos
a commercial
generic
insulation Although there are some a
or
Ababa Ababa Ababa be
=
rh
3. cath + fy
2
in deposits of anthophyllite
the U.S.
most of it is imported from Finland
longer
quiredquired for
.
fibers
and
other
other
particular propertiproepersties >:
Ttehrme Assibxestos is coarmemercial naturanaltulralyy for Whyparticular as com chrysotile Chrysotile apart from occurring asbestiform minerals that
It used primarily a filler
--
Use are fibrous hydrated metal silicates . polypropylene and in insulating ma- : -
advantages varieties divided into two terials comparison of the four Among the several
classes
serpentine and amphibole -... Evarieties of asbestos which are
crystal
mercial importance is
chrysotile
* the
which set it
and
serpentine amphibole minerals based presented in . their
onlymember structure widespread and Chrysotile is the
- Table 2. It should be noted that there for its
while increasing availability availability me serpentine class
the amphiboles are significant differences between age are world
include
include with regard include
crocidolite
amosite antho chrysotile and amphiboles
chanical strength flexibility
content soft- phyllite tremolite and actinolite to chemical composition and certain surface charge low iron
of
account
us-
positive
Chrysotile is by far the most physical physical properties _
.
_
.
conservatively estimatedthat chryso- variety
-
variety and accounts for over 95 of
.
U.S. consumption as noted in Table
1
gure
.. Where is Asbestos
. Used and Why
-
tile
in
tile asbestos is used in over 3,000 ap-
plications and in most of these appli-
Crocidolite also known as blue asbestos is imported from South Africa
and good Because of its high mechanical
strength
resistance to acids
and alkalis it is used to reinforce a
limited variety of plastics where its
pronounced color is not objectionable
Amosite also imported from South
Africa is used primarily in thermal
So
she
Coden
ute
Society's Man-
agement Seminar held Golden San Francisco Man-
JuneMetals Div Niagara Falls N.Y. 14302
VOL 47 No. 611 December 1975
Asbestos has served mankind for for which no replacement is readily
more than 100 years in a broad vari-
available
shows
that ety of applications The general areas '
The information in Table 1 shows
_ in which asbestos is used in the U.S.
that the use chrysotile asbestos and
are shown in Table 3. Based on infor-
its share of the total market are stead-
-
mation from asbestos producers and
ily increasing This is due partly to
consumption surveys it is estimated
that the plastics
about
industry uses
technical advances permitting the broader use of chrysotile in plastics
33 of the 800,000 tons consumed an-
|
nually which makes it the largest "
asbuse er s of t asbo estsos fiber
The largest uses of asbestos by the
and the general decline in the use of
asbestos in certain fireprooafndining-
sulating materials In addition there is increasing evidence that crocidolite
plastics industry are in asbestos and amosite are more hazardous to
sale OREN ee
meme
eR ee - ee ae an mimes
a
~
-19 -19
a
Year
1967
1968 1969 1970 1971
*
Table AppaApparrent ent U.S. ConsCuonsmumpptiton ion of AsbesAsbtesotoss Tons
Total
+ Chrysotile
Amosite
Crocidalite
720,583 817,563 784,321 728,131
"
686,044 95 775,711
12,558
14,917
20,467 13,965 1.7 10,558
3/5
749,708
96
>
3"
14,618
1.9
5
1.3
> =~695,770 96
~* 14,261 2.0 ce. *. 8,9361.2 <
.
_ 6,953 0.9
Table Apparent U.S. Consumption of Asbestos
By General Use Areas
Area of Use General Percent of Consumption
* 7
;
Friction and packing
-
1972
and
a Information
on import
production
Bureau of Mines Minerals Yearbooks - parentheses
b Percent of total shown in parentheses
= A ery
3 _ Insulation rievo
we take< f Pi Textiles 22.2 8
wherever possible cigaretteftisbhmeaorkting atndhelung cwahnocehravaes is evidenceon of an aosfsocmimaaintxeiytvouinyrdeeoeasfnrcsmmeieansgeoso- . Hazard -- caused solely of excess risk aasbsesb tosestAnoothser evidence - chrysotile yon caused solely
inhalation inhalation cers aeo,f StEhHe Inta ernationaA l gAe gennc cyy for '
oC
human health than chrysotile Since or
by inhalation
:* cers
Research
Cancer a division of the
1970 the use of crocidolite in Britain _ *
important con-- World Health Organization There
has been restricted after panel of sideration is the relation between ;
.
*
experts concluded there was suffi
Dr. E. C. Hammond and thelial tumors with air pollution in
cient evidence to suggest other types
reported by Selikoff In this study they
the neighbcroocidr olithe ood
of fibre should be substituted for Dr. I. J.
__
seems clear then :,'" and of factories using
*
as-
crocidolite
reported
It
bestos fiber types The
re .,
on any SeDAD aR at GE
2 . that lung cancer is wuonrckoermsmon among ... lates to conditions of
~~
What isthe Asbestos Hazasbar_~*d *
insulation
_
and
There is
history of cigarette smoking
.
of no
.-
=
is accepted if the asbestos air . It readilyreadily
that asbestos
. no that risk increased
such in-
of mesotheliomas from
7.
is not great neighborhood like many other foreign bodies can
+"
crease
increased =-- venta
EER te mt Seth
A
tate neighborhood mesothelioma
and amo +
neighborhood of chrysotile amo -
mesothelioma mesothelioma has cause
disabling
lung
damage pul- ttohird disease mesothelioma mesothelioma
commonly
mesothemelsoithoelmioama as asbestosis This disease and
raasorciateed of bronchogenic carcinoma lung can-
mesothelioma
.persons erecntxly poesedxposbedeen asbesMteosos- ences on
.persons
is
s
is an extremely
or causesof
thelioma common as- cer are the two most
~
related diseases It isimportant
peritoneum to note that based on epidemiological
In contrtao sthte diseases the data these diseases have occurred
. that primarily in workers with high long ent term exposures to asbestos dust It is
high fiber and noted.re- noted.re- of further interest that one
not in- searcher has reported that neither of
these diseases is peculiarly related to
of
the lining of
the
chest
pleura or .
the abdominal cavity
lung
there +
is some evidence
mesothelioma
can occur after brief exposures to
relatively
levels
According to the member Ad-
visory Committee on Asbestos Can-
oe ypog
_
deyTt
dertoais
4.
also also concluded that
no evidence of lung damage by asbestos to the general public
such evidence as there is does dicate any risk of cancer resulting
.
< =".
zt
<! -
from asbestos fibers present in water .
Minerals
Minerals
><
beverages food or in the fluids used 2+".
~ 3 Table Comparative Data for Asbestos
~~
for the
~ re.
administration druggseneere"al of Formula
the is oF
Chrysotile
Crocidolite
Amosite 7
Anthophyllite 85O
3MgO2SiO No
1O .5MgO 7M O
While While
seems be
vO
that public not <.
.
2"
-* agreement
=
asbestos it
is also that excessive long- danger from Composition % : ~
49-53 49-53 ON 56-58
"' any present recognized
56-58 term SiO
we
37-44 ne
49-53 we
-
a
34 i!
-
occupational exposure can cause man- |
MgO
39-44 Ong
Cele" 54-44 ! too 2 uo
problems Also man-
FeO
Los
i
13-202
F
1:
made emissions are not controlled . -
Fe
Al
-O
HO
i
.
.
+
-5 " --
12-15
7
2-5 ;
|
29
sreg. gg. nT Be
%a
:
tA.
ez
Dat tet
Ome
W6
C
O
Na 22 7%"
NaO
aA
Ste oe
me
Crystals -.
Fine fibers
__
"
Color
Gray green _
Texture
Soft silky
Brittle fibers
Blue
Harsh . Good
-
-- Prismatic .
brown
Harsh
Good
Prismatic
Gray Harsh
Poor
Flexibility ;
Hardness mohs
Fiber diameter A
Tensile mpsi
.
..
.
254 .180-300 800 Positive
4
600
5.5-6 -
600-900
-
200
"
. Negative .
5.5-6
Surface charge . Resistance to acid Resistance to alkali
Poor Good
Good
_ Fair eo
ead
. Good .vig
~
-
mee
.
v
Plastics Encyclopedia 1978 and Encyclopedia of Chem a Sources Modern
Tech Vol 2
could could approach harmful levels -
been enacted by the During the past two years significant
legislation has
reduce ~ and
Federal government to
control occupational expostuoraes-
environment Addi- bestos fibers
emissions to the
tional standards
environment
environment
or regulations
have
been
proposed enacbt y e mad ny
states and local
.E
.
a ne on
Summary of OSHA Regulations
The William Occupational on Safety and Health Act of 1970 be-
came effective April 28 1971 with
repo ,7e
wre
Journal of Paint TechnolOGY
*
the following Congressional purpose
Improper interpretation of the reg-
EPA Standards
mercury identified employees To assure so far as possible every ulations has created many miscon-
Whereas OSHA is responsible for
working man and woman in the na-
ceptions about equipment and pro-
the protection of the worker the En-
tion safe and healthful working con- cedures needed to properly use vironmental Protection Agency EPA
ditions and to preserve our human
asbestos If exposure limits are not
is charged with improving the en-
resources The Act established the 1 exceeded there are no further com-
vironment to which the general public
Occupational Safety and Health Ad- pliance requirements except for med- is exposed On March 31 1971 as- |
ministration OSHA within the De-
ical examinations Medical examina-
; bestos along with beryllium and
partment of Labor which has re- tions are required for all
;
"
hazard-
was
sponsibility for administration and
|
in
any occupation airbtooairrbnornee 3
. mercury
ous air
the
"
pollutant by the
Administra-
Administra-
we
~.
The enforcement Research and related concentrations of asbestos fibers =. of the
Emission 2
relatively simple and EPA National functions are handled by the Depart- examinations are asbestos were ~ no
tor . Standards for
then pub-
ment
of
Health
Education and should cost more than 50 per the National ' year per emplop yeere --
lished
by EPA
in
Federal Regis-
than the fare HEW through
~
and year Respirators employee clothing , ter Vol 38 No. 66 April 8 1973
Institute of Occupational Safety
Respirators and special clothing Although no numerical
operating stan- ~ dards were Health NIOSH Five million em-
are required in the construction trade
established operating ori-
ployers and 60 million of the nation's for the spray application of insulation teria are prescribedprescribemisionsetdo prevent out- or ..
- 80 million workers are covered
~
and fireproofing materials and the limit asbestos emissions the out- -
OSHA Specifically excluded . from removal of such materTihias lspse- ; side air from asbestos mills roadways ~:
coverage are government employees cial protection is not required for any certain manufacturing operations - .
unless exposure and operations which are protected other use of asbestos
~
building demolition and the spray
under other federal health and safety - limits are exceeded This is also true application of materials used to in= ->.
for other as laws In a news release issued January
items such specially sulate or fireproof equipment and.
4 1972 OSHA announced a Target
change
equipped tools change rooms clothes
machinery The law further requires -.
aimed
disposalRes- that spray materials used to in-
wimiptrohvinwgorHkainzgards factors asociated ;=,laundareeriang conditions The follow- pirators not substitute en-
sulate or fireproof buildings struc- TS
shall.con ~
substances were but the law allows tures pipes conduits shall.con ing five
designated gineering
..
on
7
implemented use while controls situations situations tainless than This asbestos significantly to be the focus of initial and con-
implemented controls special situations weight basis This should significantly -"
asbestos cotton dust silica lead and the time new At present standards
have been established established only for asbes
tos although of the 8,000 toxic substances on the NIOSH list only 500
are covered by standards and many of those need updating The new Standard for Exposure to Asbestos Dust was published in the Federal Register Vol 37 No. 110 on June 7 1972. The basic exposure standard is
an hr time weighted average TWA of five fibers longer than 5 micrometers per cubic centimeter of
air The TWA limit is to be reduced
to two fibers per cubic centimeteorn
July 1 1976. A peak concentration
of 10 fibers per cubic centimeter is not to be exceeded at any time All of the fiber concentrations are those
to which an employee may be exposed without protective clothing and equipment The first basic require-
adequate
emergencies for eral public may exposed especially
adequate in and large urban Administrator frequent short assignments in
Administrator of EPA
required + Caution labels are required on prod- the Administrator of EPA =".
ucts containing asbestos except where
has determined that in order to pro
the fibers have been modified by bonding agent or other material to prevent dusting during any normal
subsequent use or handling Besides raw asbestos fiber products which
vide an ample margin of safettyo
protect the public health from as-
bestos it is necessary to control emis-
sions from major made sources .
of asbestos emissions into the atmos-
require package labeling could in- phere but that it isnot necessary to
clude dry acoustical spray products
~
and joint cements unsaturated roof- . . In this determinatitohne Admin-
ing felt and textiles and some in- ~ istrator has reloinethde National ~
sulating products made without ade- Academy of Sciences report on as- --
quate binders The labeling of prod- -bestos which concludes is ~
rS
uct does not prohibit use It
-
*
here that | should be noted
at least
the known 90 of the products containing es-
bestos the fibers are solidly locked
too important in our technology and ~~
economy for its essential use to be
stopped But because of
-
serious effects of uncontrolled inha-
into the product thereby presenting little danger of dust generation dur- .
lation of asbestos minerals in industry and uncertainty as to the shape
ing normal use and handling of the
product flee we
7 M eTTT aut
7
one
ete
<
and character of the curve in man it would tpt ar ee *
response
be highly im-
a}
ws
ment of the new standard is monitor-
ing to determine whether or not fiber concentrations are in excess of the
pliers provide a monitoring service to customers and a similar service may be obtained from state health depart-
af
JOHN L. MYERS Marketing Manager for the Calidria Asbestos Group in Union Carbide's Metals Div received his B.S. Degree in Chemical Engineering from Purdue University in 1951. Joining Union Carbide that same year he served in the Nuclear Division until 1966 when he be-
ment officials insurance carriers or
private consultants The law requires that monitoring be repeated as nec
came a Research Engineer in the asbestos group group He was
promoted 1970. vw By
to his present position in
meget cchyaty 7
2
- ..
Tanah ake 6 07
essary to ensure that employees are not exposed to levels in excess of the
OU BOTT ee ttue. ae Ute?
rake ets
VOL 47 No. 611 DECEMBER 1975
prudent to permit additional contamination of the public environment
with asbestos Continued use at min-
Table Typical Air Sampling
Results
Ceiling |
Control Measures
Asbestos producers and users are
imal risk to the public requires that Type Plant Plant -
Concentration
spending a considerable amount of
the major sources of made as-
Or Operation
Asbestos Fibers
.
time and money on various dust -
_
bestos emission into the
atmosphere and
.
defined be controlled compoundincgompoundinag eJs oa
What IndustryDoing is , similar conversion ___
i Floor Polyester tile. She ebeeet, Polyestercompounding
:si Phenoliccompounding *
WF.
1-3 Feet
tral measures Conventional means to . achieve minimum dust levels include - ~_
equipment
local
kg equipment local ventilation for saws -
and
,
to
~
=:
Associa-
Information sealants wetted operation pack- The Asbestos
Associa-
HanGydpslucmoimpnougncomdpousnds ae aging North America reports that dur-
GypsuGmypsum a
Source ing the past 30 years the asbestos - a monitoring
pel- dustry has spent millions of dollars to <
clean more leakproof
eS
andcsompounds md
vacuum
care in
_
UniwoenyCCaarbirdeboitde Corp. from
*
air bag disposal and other asbestos waste
reports "rw. YENCorp. age, 2h : handling and automatic bag openers
_ Unusual innovations includeopeners
improve mining milling and manufacturing methods The establishment of safer working conditions has been a
able level 10 fibers short avail-aa prime target and this work continues
vk
aR
fae,
ee Bt
~ Stale
et
letized asbestos special packaging
is OSHA
, 0 ante 4 .
and treated products893,05 avail- ,
able Only
chrysotile is
In able as pellets but
serves .
this product unabated and in close association with
independent Pellets -- : government agencies and
most cases the TWA exposure level a fair portion of asbestos marketSi.
would be well below OSHAstan-
-7
not only reduce dust during
were collected conventional medical researchers independent tet.
dards Most of the data
*oe
handling but they are
asbestos special The ultimate goals of the
before the installation ofany
15
e
Monitoring also available in bulk hopper cars and be industry are Reduction of work control measures
of
can
can transferred and usedin
.
*.
totally _ dust to minimum levels Protection - shows that
obviously dusty 7~~ ~
con- enclosed systemsBarring leaksthe
asbestos in of workers from
dis-
ditionscaused bymaterials other
system
system
wor wok rk
areas
is virtually
Used preclude eases Maintenance of environmental
~
than asbestosThis does not
f- ieeliminated
inbulkasbestos
warehouse shipping costs emissions at levels low enough to pre- _ the need for controlsbutit could"* pelletsalso reduce =
;
~
public faciltae shiping clude
easdah de _" change their scope and facilitatecom* e. liminate warehouse storageand
endangerment sah regulations pliance with government
handling facilitate automation reduce
Sampling iar Air aX * Becofabau d s pree ss asbestisoscleaunp and eliminate bagbag handling
frequently ordered out ofuse without - and
The
containno
withOSHA - or air are be not In order to comply
., regard to whether
hazard~binder and friableenough to
-
"
standards and to determine the need
actually dispersed dry form .
exists dueto air contamina-
in
or
or
aqueous 5 " ther o for dust control measures air monitor-
tion If acceptable dust levels are or resinoussystems with
.
conventional ing should be conducted in areas
feasible there is no need to replace shear grinding equipment
packaging where asbestos is regularly handled asbestos at the expense of product Several types of special _
packaging
suppliers or used OSHA standards require that
quality or economic penalty Gordon _ are currently available and
-
Ae: for unus- all determinations of airborne con-
Everett of EPA points out that in-
consider customer requests
centrations of asbestos fibers shall be
formation on the biological effects of
~-
ual requirements The floor tile indus-
-
oe made by the membrane filter method
asbestos is very limited and that the
try can obtain asbestos in plastic
bags - at 400-450X magnification 4 milli- effects of many substitutes have not which can be added directly to the
meter objective with phase contrast been investigated at all Before as- compounding operation Asbestos in
illumination The equipmentthan for bestos is replaced it should be cer- bleached paper bags assembled with
collecting air samplescosts less than
-
stain
that avail- . alternative 2 glue printed 2
a safer
is
soluble
with
400 andis readily available A phase
dispersible more able ~
begrunde begrunde
Bik people
.ink canadded ~~.
Obviously people more making finishes contrast microscope can be obtained
there are
directlyto
added
or
containing for as little as 600 or an existing exposed to products
_
asbes- - acoustical tile formulations
rasng
tn Cape
,
is microscope can be modified for
a Tent ~
tos than thereare to raw asbestos ' -,
Althoughwetted asbestosis not
available counting the asbestos fibers in com- fibers As noted previously more than generally .
most .
-
suppliers pliance with NIOSH criteria .
90 of the asbestos used in this coun- are working with customers to pro-
Air samples have been collected
try is in products in which the asbes-
vide dustless products When
justi- and analyzed on a regular basis by
tos is locked in or bound with ce-
fied by market demand asbestos can
the asbestos industry for years Ex- ment plastics or other bindersso be treated with water mineral spirits
cept for a few applications where dust that there is no release or at least no __
glycol or other materials
>
control is an engineering problem in- significant release of fibers in work with the
or
compatible dustry is finding that dust levels are
areas or to the environment Materials
eigr
application system "
already within acceptable standards or products with looked fibers
we
~
we
Conclusion industry's or that minimum changes are nec-
would include floor tile polyester
wait
essary to achieve compliance Al-
industry's though data on many asbestos
resins phenolics sealants coatings brake linings friction materials rub-
Asbestos is oneof
many
raw materials which involves a po
applications are not available the summary in Table 4 is typical of our
ber roofing compounds and reinforced plastics Since an abrading ac-
tential hazard when not used with
reasonable respect and care Although
measurements of dust levels during asbestos handling in various types of plants and operations The dust levels
tion on some of these products could " all forms of asbestaorse recognized
release asbestos fibers appropriate monitoring and control measures
as hazardous to health when inhaled -
excessively there is growing evidence
reported are ceiling concentrations
should be instituted if it is thought
that crocidolite and amosite are more
and it should be noted that the allow.
. that such action would release fibers
hazardous than chrysotile Fortunate-
TOLINAL OF BAINT TECHNOLO TECHNOLO
ly the plastics industry uses primarily
chrysotile asbestos and in
lockeprdimarily ucts the fibers are
to pre-
vent airborne contamination Al-
though asbestos dust levels are gen- 9
erally lower than expected industry: =':;
continues to expend large amounts of
no
oo,
we ee gw
Chrysotile asbestos is an important
and necessary raw material vital to
the nation's safety and economy and : with proper control it can be used -
safely and in compliance with govern-
ment regulations Medical scientific
government and industrial personnel.
*
References
312 Arch Environ Health 27
Nov. 1973 C. paptarnters
ee
TES
:
Ann Hyg 2 Wagner J. C.
Occup
15 61 1972
A nn FH Gemsee nad
3 Wright G. W. statement before
* ,'_. U.S. Dept. of Labor Occupational
Safety and Health hearing on pro-
~ -
,
. .
wot
0
wr
Lot
i,
os
.
oo,
.
co
.
dard March 16 1972 3 _
J. 4
Relation Cigarette Smoking Of Relation
Risk of
Cigarette Smoking To <
Asbestos
Death Cigaret e ated Disease among Insulation
Workers in the U.S.A. presented
at meeting of the Working Group
to Assess Biological Effects of As-
bestos International Agency for Re- .
search on Cancer Lyon France
Oct. 4 1972
5 Report of the Advisory Committee
Brit on Asbestos Cancers
dustr Med 30 180 1973
J. Ina
3.3 Asbestos
Safety EOE
National News 3.3 Oct. 9. 1973
Emission 3.3 National
MVE a
Standards for
Hazardous Air Pollutants Federal ;
Register April ,. 38
66 8820
No. Worker 8 P1rot9ect7ing3 Protecting "the Asbesr toe s e eae) wt
Booklet No. 101D The Asbestos
Association . Industr 9
Medicine 10
Information
America p 5 Selikoff I. J.
39
No. 4 21 April 1970.
Standard for Exposure to Asbestos
Dust Federal Register 37 No. 110
11
,
, et al
Procedures EquipmentMillipore for Mounting
Asbestos Fibres Filters and Counting
Equipment
Fibres
by Contrast
Microscopy Bureau of Occup Safety
and -
Health U.S. Dept. of Health .
1969 cation & Welfare Feb.
,
12 Asbestos
Health
Question_Per-
Question_Per-
-
-
. plexeEsxperts EngNews Y AsbestosInformation Association -:
N. W. . 2 VAS 1660 L Street ~
VOL 47. No. 611 DECEMBER 1975
Washington C. 20036