Document by2MxJpymY517Y0LEq6k4DOGg
FILE NAME: Colonial Sugar Refinery (CSR)
DATE: 0000
DOC#: CSR008
DOCUMENT DESCRIPTION: Journal Article - Survey of Dust Exposure and Lung Disease in the Asbestos-Cement Industry in New South Wales
f
Studies in Industrial Hygiene leu 24
'i I \
v
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A SURVEY OF DUST EXPOSURE AMD LUHG DISEASE IM
THE ASBES10S-CEEHT INDUSTRY IN ' i
NEW SOUTH WALES , l I
1
*1 '
\
` t
Cecil G*
Roberts and Harry M. Wh.ai.te * . -4 1
___________________ t *'
1
'
* `
`
1 ,
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4
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a suitvhTt u f II, irin
. , , ,hi ,u.D liUh
i ^ Lu..-,,.j Tum s m in
sl:UTll U T 3 _
!
njSTOHICAL
e 'f asbestosis
Probably the
V r ray* In London, Hi 1500, con-
that reported by Hontague -urr^y Vl,.0 .had been ex-
^rninfthe `ieath of a workman,
y ^ . In 1910,.
-,o/ed to asbestos dust for soia. L n -attenti.cp to the de-th
--rt-pr the tiegistrar-Genei'al had ,.,irfnai*v fibrosis", nodi
of^an asbestos worker from "acute
iD the factory
cal examinations were made oj^
aspect's -of the in-
which had employed him and tn. ^ ^ e s s ) - Serje 'investigated.
austry (e.g. dust, ven ? d but did not -rovp, that
rhl, investigation R e s t e d
^
. A later case Con-
cf nictthuarte, gr;voauopv
of
i& t g
Pecrxsp<0S6^Ci
i ^
ufbestos/othoert'*asYb6e&stcto~sblmixed
with a very Siiia:L]:,,propor^ 0o1.t10f about 2000 were examined,
fibre. In all 565 persons out of M M
factory being ;
tsheolescet ewdit. h Othfe thloonsegesetxaiii^ed^J^w er found to'hathvea tdiwfifthus_e
fibrosis of the lungs. h ? h
rhe fibrosis would bo
exposure to high dust concentpations th.*
pQfsible death
fully developed in seven to nine y r ,. after about thirteen years, with lesse
-concentrations, <as twenty-five
maturation of the fibrosis mig * figures of- dust con-
ears. Unfortunately, only
figurs apply to .
centration are shown, and most of bestos textile, industry,
processes connected only with tho
. exhaust' ventilaT
Opening and handling fdby> .."irh dust Concentration opera
tion would be regarded as a ..lgn
w o u i be common
U S ; and this is the only one listed^tnat^woul^
to both ;the asbestos
c% frmd that neither age nor
of the industry. The
incidenq, of the .
sex appeared to have any effect on the m
^
,
fibrosis.
.
1 .
j.
-n>>Tiihed. bv SB* McPln.eters
In 1956 a repoJt^ SD^ s o n s exposed t .asbestos .
of a survey of a group h n ?ndust?les. Twenty: doubtful,. dust in the asbestos-cotton Indus ^ caseB of asbestosis
twenty-five moderate and eW
, the ,,nolo, group of
were found. The average exvosune ^ aflTanced; a^bestosis
thirty-three persons with
e with- moderate asoes-
was 10.a years. ?avadoxically, t h o s e ^ ^
e with
tosis (10.5 years) had a greate
as,some evidence
advanced asbestosis (.TO* ^ ranidlv in young*?*' persons.
that asbes tosis develops more rapidly
as^stosis
Those under forty 26ilTS *Eest0SiS in 9.0 years; ;the in 9.5 years and advanced asb st 51 forty yeaj:s were
corresponding figures rf
No activating or aggrava-
fiit ^ f e S - o / S r ^ r r S b f r ^ l o s i a was observed.
.
I
I,,0 vears later the Uhl'-"" Servlce , * * < * ^
of *a^s"T * "'
&facstories. Ihe dust sample -r ^.
**ere hade of
impinger. In
Xudges^al breathing level. ^r)d of
settled dust taken from lodg
filter. ` Owens' dust (
airborne dust collected by b
dust exposure of ;
counts were used for sizing
o-vpnrs pef cubic foot
each workmen in millions pdJ t couJ t for each operation;
was found by multiplying the t and sumiaing ,the pro- ,
by the number of years JP?Bt
* total number of years
ducts so obtained.
the weighted dust cbncentration
the worker was
that period. Ifrls method of
:fslfsSgeexpyoEr e h a f C n adopted 1 thia repprt.
Since their tests were made by
^vey
Only three persons oat " 8 g i i ^ p a r t i c l e s per weighted dust concentration b^"1'; exposed to a greater
cubic root but TO fffefted by asbestosis. Frqm these
concentration were effected oy
clean-cpt cases of.
figures, the author. "TM u^ V s t c o n c e n t r a t i o n s exceeding
asbestosis were found only
fDO+ and ^becailse they . .
five million particles per cubicCentrltions, f^ve-million ,
were not found loJ du^ e rcgarded as the'threshold
S a i n e d asbestos-dust exposure until better data are avail
able.
'
. j j-j _. n t- v'ork cn asbestosis experimen
The most signifioan '
carried 'out in the '
by tally produced in aninals
United States Vorwald.
was Du
"="f ratt. t cats
nJ. animals used andidogs. From
of^theirexp erLuonts^the*authors made these ob
servations, among others.
,
1. Long chrysfitile a^ e^ S-L^ g 1`esiSiiarCto 'hu^an asbes-
chiolar fibrosis of the
mouse and'the dog.
tosis, in a l l - ^ ^ f a i l u r / o f the' mous4 and the dog
TtoereesSond M ^ o ^ Long asbesto, fibres were
necessary to produce the reaction.
^
.
2. The mode of action f ^ c h ^ i c a l ^ a n d Ippelrs^o
depend on flexing action since
fibres do not produce fib -ne-ibility destroyed by
fibres which have had their fle.iDiii^a.
,
heat.
'
' '
.
S. Evidence was pro^uced shOTving that
of 1SB million P y U j l u s per cubj.
^"" ^ a S i i i g (i.e.
0.6> fibres greater than
under 1 million asbest
ter than ten . r pI.0|Uce,.experimental
microns per cubic fooU
actual lower limit of
asbestosis in guinea P*?*; ^
to'produce ex-
^ S iS ^ S S
" c. , i i W = ,
4. Ihe duration
m-
versel^proportional0 to" the concentration of long . 1*
' r.
t
1
. rli cl `S ixi Pho ^
''
^`bout tfc million
produce a very early
posure of 50 m i U ^ );Ta [ h fibrosis u l u bo qal
,i.. * 1
~> . .
T" ,er CuOO 1(/0^ ' ^ i U t 'vvlth au ex
pel* cuuie ^ut
,K.a.
'
^ ierl4illIltla
Further conclusions reached^erv cllscontilluance of
* asbestosis ceases
A ^ ^ a t i o i of asbestos dust
dust exposure and m i 1
final ,ou Iconic of cx
did not
t>vo series of guinea , 4 ^
perimentul tuburcult.-ai- m x .
( .
exposed to that dust.
.v
,
nwRP.RTPTlOM -QjLX HFl I^DTJTBX -- -- ---------- -
_tos'industry of New
The major activity of ^ ^ t o s cement'and its
c llth Yjales is the manufacture of
^tixiii and into a largo
fabrication into flat and
^ ^ V
f
ranee of moulded products. In t l t l. illteHaed to ueal
^itn^otbe^sactions8oftho G u i t r y in . separate t e ^ . U
Ihe manufacture of
S o f t 's f e c ^ o f tSe S # S & apptoximatel* one
thousand persons.
' ' j^gment and
The raw materials used ^ eb^jiefrcul/West Australia,
ter The asbestos is received Id
fr0m'Baryulgil in
S r .s
s s -
"
Ih. c.n.nt Is " t m l j r s c l v c ^ b u l l . ^ i t n
^
rail wagons or trucks, Wili
bucket elevators? ana belts ;
conveyors. Inc conveyors feed * bin6- .* certain.amount of
which carry the cement to stc g
gainst .any nold-up
cement is received and stored in fc
asbestos are man
handled S S ^ S ^
eroups of men generally knw n . ^ . emptying and. mixing with
step is blending of the asbestM by
mix is then
shovels the contents of appropria
|
This work is
shovelled or hand-fed into the p tilues joibwn*'as ."blower
carried out by a further group, so:"^ ^ ,, n i l l s . Inc
man The pulverisers are eitner A oi
|tfa EtoraBe
Pulverised product is then W " E AE required, the blown
hn-ners usually known as fibre, rccms.
doors;tnto barrows,
asbestos is generally raked ^ out^ e" m s -or fedaters -..here
wpiehed and then wheeled to th ^
into these machines
the asbestos-cement mix is prep t*P fibre added. Towards
water is run and the weighed asbestos fibre
^ minuteS;>
Ihe end o? the beating perif !
from a conveyor belt,
a weighed quantity of cement is ^ Vese earlier stages of
She Only ttiose operatives taking P manufacturing process are llfcel
ce l s i dust, but there is a minor V
^ exposed to ex ^reclaiming dry
bu.f one which is,
scrap which gives rd
nesvuebrstehqeuleensts,staag|es0^ofd^
mainly carried out wet.
_
ner than that found in the
u|Acture where the lionesses are ht ^ C l o n e d , ' h e r e that there
j- &
.
... *1
f
is little exposure to c-c^nt us opp*.
t-O i*iIIJoLLUb tl*-ib a
.,iid in any case cement dust aues not constitute tiny Various
Hazard to the luncs.
I
From the tide mill or beater the liquid mix oi
ashes tos-cement is run into an agitator-whonde it it- ^
as required on to felt belts of the su^et waiting a^ "in':b,t Here most of the water is removed by filtration and suction
through the belt. The sheet how in course of .preparation
S ?Mnsfe?red
tlie belt tn to rollers of circwufemiee
appropriate to the length of the sneet required, aria is ,
built up to a desired thickness as tne rollprsrotate. .It
B ay be cut and removed from the rollers eitner.manually or
m-.chunicully. For a flat sheet, it is then stacked between
steel lates, but when a corrugated sheet is Required it
is first hand moulded on a corrugated steel'sheet and then
stacked between corrugated sheets. In some cqses the nun_ling
of these wet sheets is entirely manual and In ethers highly
mechanise:. The sheets are then allowed to stand.for curing
ana drying. The reaction welch takes place is exothermic
and hastens the process. Some sneets are taken away fro.m
the machines for the manufacture of a wide range oi moulded
articles. After moulding, these articles are,placed in
dryers to expedite the curing and drying process and so
increase tne turnover of moulds.
.
:
After the sheets have been cured olid dried, they
are in most instances trimmed to size by guillotine, bana-
sciws and emery wheels, a recent devclopment/has beamvdt
trimming of the sheets to the final size pfiojr. to tne
curing and drying process. In this way 'the amount of dry
scrao is being reduced and with it the exposure to aust
already mentioned in connection with d^y scrap.
ASgpS p,:.p:ur OF THE DUFT l.yVOSUHK --
1 14 . \
In liew South V.'ales, dust concentrations are usually determined by the Owens* dust counter, an average of several counts being maae over a suitablq period of time usually one half-hour or mere. However1, in order to be able to compare our figures with corresponding American ones and with the American standard of five million par ticles per cubic foot, it has become customary to use the midget impinger when sampling atmospheres containing air
borne asbestos.
.
* '
.
The midget impinger, a more portable development
of the Greenburg-Smith impinger, is a jet-type, instrument
in which 0.1 cubic feet of air per minute is dravaa through
a one-millimetre orifice, and impinged on toithe flask
bottom five millimetres below. The flask contains ten
cubic centimetres of a collecting liquid which, in this Division is usually twenty percent ethyl alcohol in distilled
water. he liquid is carefully filtered before use through
a double thickness of filter paper in-order to. remove any
suspended dust.
, . .
After test, the collecting liquid, is- diluted to a suitable volume. This volume depends on visual assessment of the amount of dust collected in the liquid^ -An aliquot part is then run into a counting chamber. . The -on.e we use is a Spencer bright-line haemacytometer. From-the cell count, the total number of particles in the'collecting liquid can be calculated. The volume in cubic feet.of air .samples is found by dividing the time in minutes.of sampling by ten. Division of the former quantity uy the latter gives
the dust concentration in particles per cubic -foot.
f
There are 1k ,m . ...av-mh-C d-
U ib^dVcU tube's in
tl ie u s e of trie m i d g e t i - z h j ^ r . I'tie ^ic roscobl ; sei-Ujj
. i r t i c l ^ a -bui-uv* one m i d on
used for counting does not rtsolfe p - . ,
lol4,cr
in ci7(i This may not be suen a disadvantage 11
particles of LSestos (,,.g. litres over ten nicrous m length) have the signillcance ascribed t them.by seme invessttiigeaattoorrss.. SShhaatttteerriinngg ooff the llaar-r.^eir- ppaarrttiicelless tends to
cm- but this defect is con.cn to ull jet ,,gupiiiig 111
ruments ln hieb the austy alt- is <*ravn turqagh an orlde
assessment of the relative dustiness of the dtfierent jbases of an operation, nor may statistical analysip be made of
the result.
Generally, dust samples taken in
=u TM ey ' f
covered a period of ten minutes, or longei if^l-1
the operation being tested had not been covere .
1
e x p o s e of each workman in millions of p-urticle-yours per
cubic foot was determined by multiplying 1trie -dust count icr
each operation by the number of pears ne had spent on it,
and sumuing the products so obtained.
\
The weaknesses of this method of assessing a .
workman's dust exposure are obvious. It assumes that m e
dust concentration obtained by test is approximately tue mean
dust concentration to which that man has been exposed over a
period of years; it ignores both short-term, (<e;.g. hourly)
fluctuations in the dustiness as well as long-term (e.g. .
over periods of years) trends towards more dusty or less t
dusty conditionz. The former can be minimised,by making
more dust tests at all working points, but the< latter ^cannot
be estimated without having taken tests some years ueiord
m the same places. Unfortunately, this had not been done
in any of the factories concerned.
'* -
Full details of the dust tests'taken, are not given
in tuis report but, in Table 1, wuieh fellows,; the average,
the minimum and the maximum aust counts' are shown for tne.
processes described above. Tuey are set out Ip des-cenuing
order of average dustiness.
-
Position of Tests
Asbestos pulverisers & disintegrators
Tide Mills and Beaters
Scrap bagging points
Ho* ul Tests
4
6
S
Table 1
Nature of Work
Asbestos unbagged,
blended by saovel
L fed to uisinteg-
rator
.
lildget Impinger Count
mill, part./cub.
iAverage
... r ' t \ '
Low est
': lb.7 O
ft. high"
est
4.7
* 1 '. 1,,
- Blown asbestos usu 1,, .
ally raked into bar 1f1 :.6 0.1
7.6
rows & wheeled to 11,"! .
beater. Y/et-mixed < -i
with cement in beater .* ^
Pulverised & blown scrap filled into `
,M
4
t
2,. 6
0.8
5.5
bags from hoppers r***. *
`
f
-
^ + x.-,i r,r 175 had been eB^loybd for
surveyed, 95 cut ox a tot<~l o
cf considerable import
less than 5 years, Mentioned* asbestosis hai .'only been
for. as already mentioned,
e
'even vdth .
found to occur after prolonge
tUe Ji^ase.is rare
i o S in very high dust concentrations, tne^o Vrthenaore,
in workers with less than 5 ye.ro
` rtil different Jobs
aanv of those surveyed had during their ea.loyuent in t
and there uas a ^ ^ r/ of sorvi\;e to have
within tuc
individual!^ exPosuro r
C u ;1 - i-c OJi jei-
o be ^c.-Ul 1 lo- CeUip-I'llJ
tion of tnc beli, lC^' oat wl 1 7b,
employee
LfiO dust ccuctntru Lii_ia ouS or. tuCiaVC ia^c 0.0
Table 2
Distribution of Employees on Various Types of Wn-r-v Tested ''< TM rT` nr Rnrvev
----------- -- -- Type of Work
1 ""
' 1A-. of , Employees^
- {' l
Asbestos Pulverisers k Disintegrators
18 . <" .
Tide Hills & Beaters
42
,' .
Scrap bagging pointsSi Fibre Rooms Cutters k Bandsaws
o
*
f
'*i '
* ro -
1* . ) . ). '
Scrap Reclamation Plant
5
, '
General factory atmosphere (handling, moulding wet sheets)
i 1 1 ;
105 -
--1 '
--
TOTAL
175, ' : .
T-------------------------- --- ------ ( "
Ho employees occupied entirely on th'i^
work.
' < t
million particles per cubic foot and such exposure cun be regarded as negligible. Having regard to the tw6>factors of turnover of job and widely different concentrations- of dust experienced on different processes, it was considered that a very suitable method of assessing the individual's exposure
to oust y u s to measure it in terms of partiele-rye'ars, .per cubic foot. For this purpose dust concentrations for each process cere taken as those found at the time ojf the survey. In the factories where the survey was carried oi}t, it seemedprobable that dust conditions had been fairly stable for a considerable period.- nevertheless, the possibility of dust con centrations varying from time to time cannot be dpccluded and the estimate of exposure can be no more than an approximation. The results obtained by tnis method are classified in Table 4.
'
Table 4
- '
'
I ..
'
i
'
1 , '
Classification of Individual Exposure to Dust
H O 1
H CD
Million particles per cubic foot x vears 0-4 5-9
25 - 49 50 - 99 100 and over
TOTAL
Ho. of , Employees ,,
> i
127
1
16 ' ,
11
o .;
3 `
175
,
LJ V -i- G U S S Li i \ ;
.. M I t u i U u O l l O i - i l C l ' C 1., -*I^i ' ` 'C^ 4-- d
r^j,.-rfud to, nave sho.:.i tu^t
ti,,is is ao^ lively a..
,
occur unless exposure nas exceecea b million ^urticles for
more tiu:n b years, that is to say 25 million' parwicle-y~ars.
It will be seen from the table that in only 14 oases had this
level of exposure been reached and in view o f this a ion
incidence of asbestosis viu to be expected ana was, in
fact, found.
. . !.
1
CLINICAL AMD X-RAY FINDINGS
. 1.
f
The clinical examination of all the subjects
was carried out by medical officers of the Division of '<
Industrial Hygiene and chest x-rays, either by.the Tuberculosis
Division of the Health Department or by the consultant radio
logists to the Division. For the x-ray examinations 14" !x 1111
films were used in all cases, Lucre exposure had reached a l o v d
at wuich asbestosis might be expected, the films were re
viewed by two or more persons skilled in the assessment of
such films and the final judgement on the film was based oy
one of us (C.G.H.) on the general consensus, of opinions given
by tne viewers. In reaching the diagnosis the' clinical
findings were taken into consideration, but tjhe clinical
evidence of disease was negligible and in only, 'two cases
did the symptomatology contribute to a diagnosis of as
bestosis. The following table related the cases of asbes
tosis to dust exposure.
Table 5
, 1 I t.
Incidence of Asbestosis related to D^st-
Exposure
i '
Exposure in Million particle-years per cubic foot
Less than 10
10-24
25 - 49
Persons Lxposed
145. . 16 11
_ .Persons
Affected i .1
t . ' t
;'o '
A
\
'
,. * '
2 '
i
'
' 4 '
50-99
,
100 and over
TOTAL
0 .
< ;-0
. i
1 r '
5 i'<3
175
1 9
. i,
1 fI
'
* .
,
`
!
*
It will be seen that only two cases 'of asbestosis
occurred among men with less than 25 million particle-years
per cubic foot exposure. In both these cases ;the estimated
exposure was 15 million particle--years per cubic foot.
Dreessen et al, whose survey has already been referred to
foui.ldi l i5 iuCiiuspeu ritni c1l e9-1y e -errst o ipoer v.Citunbicexjf^ooutilu.re 1o f1 nl eass s bethenan
.cin tea
out
tuat
such
e, itiuiaticis
of
1
exposure 'are
lo
more
than ayjjt cxiaiu.Lioiis u.iiO it is Quito jacssible that these stray
cases ..here exposure vas apparently within tn& Units of
safety v.-re at some period exposed to Higher concentrations
of dust than v;ere found to exist during the survey on the
processes where the men had worked. The incidence of cases,
four out of eleven persons exposed at the 5-9 million 1
particle-years per cubic foot level of exposure is con- '
siderably higher than that found by Lreessen, (iiamely three
cases out of eighty-four persons exposed. Itis interest
ing that the small number of three persons who had an ex
posure of over 100 million particle-years per cubic foot all
snowed signs of asbestosis compared with roughly half in'
hreosen's survey. However, the numbers with'nign lev--Is'
7 Me2> osure
in our survey are so small' in comparison
that tne differences mentioned are of no'
statistical significance.
. !
* (I
.
Advanced stages of asbestosis are seldom found!
e n s u r e of less than 100 million particle-years per
thpi5ifCOt and
tuis survey only one case was found where
`i L f h n f ?hC0Ula be regarded as having passed the earl? utage anu the x-ray revealed the characteristic ground ^lass
e ^Po "e wasf 1l67M m?il?lionflpealrdtLi`clAe-"yetar`rlss pcearsec'utibhiecg^faooit.e S SS
ci";enee ,, / - i ! f s!?0,'s
relationship between the in-:
bes-ttooss aduSsstt." ihe latter is notiennegcthessoafrielxyb imdreen ttio casw-m-.
occupations" (ilT entt1f the ljldustry (Iable h / lor certain
"posuii to fc;Bi A t `Cll"iari' dellTery
have no
1
Table 6
t
Incidence of Asbestosis related to 1
Exposure Time
, <
i.
\
--
Exposure Time in years
Persons' 'Persons. Exposed Affep'ted -
Less than 5 5 -'9.9
10 -19.9 - 20 and over
TOTAL
. 1
C2 O i--1
42 .
1 ' ', t *
5, * 4
26 ' ' 2 '
. i
5
1' '
1 .
i `
i *
175
9.- `
, Xt wil1 be seen ttiat only about'one
S ? l c t S r^ i L f l b 0u t StS tha" flT e y e a rs '
five years. e x p o S r f s ^ e f S i g n f o ? L ^ **"?
'
- cu xu co-ses {6J0) in 88 persons exposed for
r
les- trian five years, and 03
(40; ) 1r.'O ,c r s c h s Luc .
V e m: S T A M M S l i ^ n ^
s ^ ^ w s ssrsA S tt'- * - ~
testos texti
relatioiiship between
A ^ ^ r s t e s t o s l f a i the .eiitod dust conceu- the incidence of usbestobxa
trati on, is given below.
i
'
Table 7
t
in this table nearly three
cent^of the^orlouen
exposed to a weighted dust c a n c e l ectea. . So were
t
million ^ a r W e i g h t e d dust concentration.**di ^
of those exposed to ?
cubic foot.,Corresponding
million or nore particles p
et i V;ere *-3 out of 108
f i b res from the report of ^reessen g^ioyees!. (or 21) . It
emtloyeos (or 9 *
? L i ? L S t d i f f e r ^ between
o u r l l d u r l s r - S ' * 'is table, end tbe orrespondi *
American ones.
, 1
.
m e number of ? . f " *'| S \ * S & E , S T i ^ t S n might b*r expected.
Table 8
1
,
I ,..
i . .'
Cases of B..pir?tor, Disease other t * *
^
Disease
Tuberculosis - Active
ii
Healed
Bronchitis
Other
TOTAL
Humber "it, nf Cases >i'_
4
1; . r
. n /. ;
'
5
*
A'"
. * '
*
-------- -
In the two cases r hc. i.ve .oiluon-ry tuberculosis
,e^se was c<-riy :*nu e>-~
>covoi cl Ly' tf he u.'ts'r-ut*rvreny',' ] the i l l i o n and C
^article-
cne
suggest -lCy ^ t; ul,Jtlsy ac undergone sanatorium treat
ment four teen**years^reviously and - c e t e e ^ p l o ^
*.v,p industry for nine years v.itn an exposure o-r *-b mill - .
par title- yea rs ,,er cubic foot v:ltUout mere being any .
evidence of re-activation of the disease.
^
In eight of tne eleven cases of brpAchitis ex
posure to dust had amounted to only 5
'Pa:T.t,icle"
vears per cubic foot or less. In the remaining tnree ca^us,
exposures were `6. 17 and 14 million particle-years per
cubic foot respectively, and in these cases jjLt/ispos&i _
that dust exposure may fiave been an aggravating fdC or
in their disease. The undesirability of persons pith .
evidence of respiratory disease being mployed in the uusty
sections of this industry are obvious and the finding of^ evidence of past or present respiratory disease in cases
out of the 175 cases surveyed emphasises the desirability
in this industry of pre-employment medical examination,
including chest x-ray.
CONCLUSIONS
( '
The results of this survey confirm the experience
cf earlier ones in regard to the quantitative relationship
between dust exposure and the onset and development of
asbestosis. However, in our survey, the percentage of persons
affected was i.ess because the dust concentrations of the
working environment were in general lower. Nevertheless,'
processes were found where the dust concentrations were high
enough to lead inevitably to the development -o'f asbestosis.
provided the employees remained long enough infthose particular
lobs. Fortunately, these processes employ relatively few
workmen, but It Is recommended that steps be taken to give
these men greater protection against dust. , *t ".
.
There are three main methods of duct;suppression.
Firstly, certain dusty hand work could be^ mechanised, as 'the
following shows. Prior to this survey, one firm had installed
a screw conveyor to transport the blown asbestos from the fiore
rooms to the tide mills; since the survey, the-same firm has
installed a belt conveyor to feed the dry nixea asbestos to
the pulveriser It Is considered that both these measures
have lessened the exposure to asbestos uust. ,Such improvements
do not entirely eliminate tne exposure to dusttslnce there
are occasions, such as during repairs or uuripg; the complete
emptying of fibre rooms, when men may have toenter conrined
spaces and snovel the fibre for short periods. in these
short periods, an approved type of dust respirator would afford
\' i ' adequate protection.
, /
Secondly, the asbestos could be wetted, eitrier with
water sprays or with oil sprays. However, thid renders both
mechanical and pneumatic transportation of the .-fibres difficult,
because the wetted mineral tends to adhere to,the sides ol
ducts, conveyors, etc.
r>
'
Thirdly, exhaust ventilation could be'provided a.t certain dusty working points, with partial enclosure of these points in order to increase the effect of the-exhaust. A< minimum air movement of 50 feet per minute across the access opening in the enclosure is suggested. Such an-,ait movement would tend to carry away the fibre, hut this.copld, of course,
-lc/
be rec ovoreu in bag filter's. Drt.essen c t . J give tiibles siioi.xng dust concentrati(ns citn curd j.ihcut exhaust venti lation. For pi-ocesses cannon to both th= asbestos-cement and t-xtile sections of Lire industry, reductions in dusti ness of u to 90/2 were achieved with exhaust air Id ov.'s of up to 1000 cubic feet per minute. Processes which lend them selves to the use of exhaust ventilation with partial en closure Include unbagging and blending the asbelstos an.j feeding the dry mix into the pulveriser. In %\ie l a k e r ' case the air used to blow the crushed'uabesLos 'to the fibre rooms serves to ventilate the crusher intake, <but additional exhaust air and partial enclosure may also pripy.e -necessary.
In addition to the use of these measures it is 1
suggested that employees working in the dustier'sections af the industry be adequately supervised medically! Such
tri^nn^T011 woyld include pre-employment examinations and
triennial examinations, including x-rays, thereafter.
'
,, , ..
?ncf k ie eak ier stages of manufacture are passed
ana the v/et mix is being prepared in the tide m'ills the
Si r - C011
wdfch the possible exception of'*those
reclamation plants, and some cutters and saws
cease to be significant. Therefore, over a major part'of
the process there is no call for greater aedichl o?hygienic
measures tnan is desirable in industry generally',
ACO;UV7LEDGDDI; TS
i
1 ' -
' 1
t
r co-op^tSf
i r rzuLthis " f f rs- jsbesto, Products Fty. Ltd., James Habile l Co Ptv
of the clinical examination!:
'
C^ rled out most
REFe r e m c i -:r
. '
i
*
1, Murray, M., Charing Cross Hospital Gazette'(1900)
U.s. Government Printing Office (1938)..
;
5.
* 41*