Document rnqXed2xoJ0LYJrXw9OaoZQr
1 inn-
ASBESTOS INTERNATIONAL ASSOCIATION^!
(Limited by Gu*r*ntec)
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68 GLOUCESTER PLACE, LONDON WtH jHL
MEMORANDUM
^
TO: Member Associations FROM: Director General"
AIA/7/3/PROD 12 February* 1981
**Asbestos 6 Health in the Friction Material Industry"
The airshed position paper on Asbestos A Health in the Friction Material Industry is forwarded for information. It has been authorised by the Executive -Coonittec who recommend that it should be used as a background reference paper to help members deal with questions in asbestos and health which may arise.
**
FMSI-0355
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>:yros Aim it/its ir ?f.-: raicucm
Th Prqbleo
lirpoKure to eebertoe dust Is rseosnisod ss o potential occupatlonl hazard.
Jcr>r.r vur>: people exposed to high concentrations of respirable asbestos
drat, (ench as is hnovn to have occurred Virfore present day dust control
r+apurcs and vork procedures were introduced) cases of career and
erb^slfiris have been reported, throughout the world. * 1; The difficulty
of reliably identifying the occupational hietory of those where health
hts Ken effected ."**ny years after hec resulted in any contact vitk
--
aebertos bsins reerried vith caution snd ell neteriels containing asbestos heir.' attached frdircrireinately.
Since friction naterisl ie widely recognised as one of the products for V'Mnh ae'.eetoF is rn inmorteni ingredient, it has attracted euch attention. Ir.'crd, the asbestos industry, in remindins everyone of the vital role played by asbestos in brake linings, has atisulated such attention. TV'eythclcs* the occupational health record of tha asbestos frici.oa ttrrtrl Industry is good and only a few cases of esbestos-relatsd disease m on record. Hovevrr, tits widespread use of friction notarial in all types of vah<files has raised the aueetion of potential pollution of the environment with ea aasuasd con*euent dancer to the health of the c*nere.l public.
T.j fraction notarial industry, therofero, he: two basic problems. The I'z"*., lh: occuprtlnnal health probles, has in cany erei K-:r. resolved. Fovv*r( the lndvtetrs* surt continue to ensure that those eaployoA in the ^'ur.'fjrture of these mtcrisis are not exposed to dust levels which are
An sxtonsion -f this pr^blsa is the need to or ^re that workers crylryod in the suVssiwvnt use os lriotlon naterisls, ti-ctr in tbs Fitting of the products or the aalotcnanee of vshiclss, axe not exposed so hc-rcfcl dust levels.
O
The other problem for the Industry, that of possible environmental pollution, is aort difficult to resolve, based as it is on eaotlonal anxieties (vhich are is no way justified by the evidence). A eliaate of concern for the effect on the environaent of expanding towns and industries has led to the Botox vehicle being Included ae significant factor in this pollution. This feet together with the publicity gives to eebestoa and Its
4 classification as carcinogen have all eonbined to lead people to question the use of asbestos-based component* Is aotor vehicles.
I The eutoootiv* industry la also under attack for a nuaber of other reasesa, (e.g. pollution, waste of resources and congestion) and vould gladly be***
without the asbestos problea although it oust accept that for son* years, current laodels of aotor cars will need asbestos-oontaining material for replacement!. The friction saterial industry Itself suet therefore dispel anxieties about asbestos-containing products in notor vehicles by ensuring that the existing reassuring evidence' is made manifest and is properly understood.
Tackling the Problea
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In order to tackle the problea most effectively, it is Important that the * origins, investigations and remedial aeasures Involved should be veil understood. This Is especially necessary since the existence of the friction cattrial environmental problea it to a large extent based on confusing two very different phenomena; on the one hand the occupational health experience and dust exposure date related to manufacture (and the subsequent fitting and servicing operations sometime called "para-occupational . and on the other hand an aesuaed eolation of similar duet Into the general environaent as a result of the dally wearing down of brake linings and clutch faeings. An exaaple of this confusion may be seen la the evidence
given to the Vt Asbestos Advisory Coaaittee, where claims that the general mblic are et risk are supported solely by reference to survey of aotor vehicle maintenance workers.^
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These f*cta_vill be reviewed under three heading!, the firat two covering the Occupational areas of Manufacturing;and Servicing, and the third heading covering that of the General Environment.
Manufacture of Friction Materials
There is ample evidence to suggest that, in the manufacture of friction
materials, the concentration of asbestos dust compares favourably with that found in most other modern asbestos operations. Vithin the last ten years efforts to observe a 2 f/ml* standard have led to further improvements in dust control and ,there are now many operations where levels well below this maximum allowable concentration are achieved^.
4
Very few cases of asbestos-related disease arising from friction materiart"
manufacture have been reported.
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In evidence presented to the IK Advisory Committee,^ Ferodo Limited, who
have been using asbestos in brake and clutch linings since 1910, reported
8 cases of mesothelioma and 5 cases of asbestosis. The mesothelioma
.
cases had all been exposed in the manufacture of railway brake blocks
. between 1928 and 1933 or during the war years up to 1943, to crocidolite
as veil as to the chrysotile asbestos more generally used throughout
the plant. The asbestosis cases ware all involved in mixing processes
where masks should bsve bsan worn.
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In tha same volume of' evidence, o report from the two Cepe Industries1
factories manufacturing both textiles end friction material (one since
1901 and tha other since 1923) cites 9 esses of asbestosis and no esse
of mesothelioma.
**
*
Ferodo report that "many millions of man hours have bsen worksd on finishing
operations of asbestos-based materials; though the dust eoncontrations .
associated with thsse vara at one tiam vary high, there
*
f/ml - (asbestos) fibre^ per millitre
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has net been" a ainjle diagnosis of aebeetosie aa a result of this exposure". In core recent years (l?68 - 1976) however, average concentrations vore well below 2 f/nl following contir.ioua Iciprovc-rw-nte in dust extraction methods.
An investigation in 1975 by Heidemanns, Kuhnen, Schvtz and Pxoeh*cka^
into dust hazards which might ba associated with the nanufacture and
us* of erbestoa-cent* nlnj friction aaterlals (uptetei in the Research
7
"aport of the Gerr;*n j-enifsgenosscnschaften c* ootea concentrations of nicre-dwat in the range of 0.09 to 0.20 wg/c' during grind;rg, drilling,
sawing, turning and rilling operations (the current
value ie
0.10 r.g/nv or 2 f/sls on this haaia the current range ia 1.8 f/nl to * 4 f/rl), on average just belov or just above 0.1J cg/s^ or 5-f/nl.
Fuch operations, tinless subject tc dust control, will erit duet containing
oabestos. A number of surveys of such operations have been carried out
in Cerrsny 7'9* F*
USA 15.14 J5.1fi17 a;:i
5.59 tnd
it is clear that, under son* conditions of voii'inj and where euch operations are ezrried out contlnuouely, duet concentrations above ? f/nl (or tha 7RX of 0.10 r.g/n') can ba raaebad. Thr-re is son* tvidence of affects on health
ercocig r*n engaged for a long period on such* work. Medical and epidemiological investigation* by Preferaor Vhltovltz, Valantin and others ^ on vr-rkirs who
had been contlnvounly exposod fo? at laaat 10 and up to 29 years to asbestos *rt suggest* a ainilar risk level for nen employed on finishing operations
g^irdlrg and drilling) in tha autonotiva industry, to the risk Israel of trr*rer in th* renufsettling industry 7,9
It vr i>otd thst tha automotive Industry group studied had had long a
cj^arur'/ free* a vary tarly age. A group of nan carrying out brake
ITS Technical Control limit
* Out of 94 workers (including 45 woner.) in mcnuftct jrlrc. thers ware 3
probable cases of msbestosis-and 111>osaible". i&iony A3 man employed
in finishing operations on brake lining la tha autonotlve industry.
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caJnttmnee_sorvices with exposure primarily during the cleaning and brushing out of 'brake drum duet gave little evidence of inhalation effects in spite of long years of exposure.
Professor Selikoff's Investigations 19 quoted indications of abnormalities
in 32 out of 67 motor vehiclt mechanics (6 out of 39 vith five or sore
ycare intermittent exposure shoved signs on X-ray of changes consistent
'
vith asbeatosle). Another report of the seme investigation quoted 2<J4
of 9> bril:t service mechanics shoving chest shnorrjtlitiss not nseessarily
ar.tcstoc-related and It is emphasised that there vers no confirmed eases
of asbestos-related disease. Dust levels quoted in connection vith this
Investigation (in USA) ' 1 refer to mean concentrations for blov-out ^ -
of brake druas, grinding of used linings and bevelling of new linings of *
` 15.9 3-8, and 37>3 f/ml respectively - much higher than any found by any
other researchers. J7o Information Is provided as to the duration of
these samples - they are frequently referred to as peek concentrations or
the mean of a number of such measurements. It is also clear that in ths
case of bloving out of brake drums, no ssbestos fibres vera visible by optical
microscopy; some ehrysotile vas Identified by X-ray diffraction. Fibres
Identified by electron microscopy vers all belov the minimus site apecifled
fk
in the definition of ssbestos flbrs (l.e. 5 )u 1 length) . It should be
noted thet the methods of sampling sad ths criteria for measurement of
occupational environment! did not conform to ths methods used by
governmental agencies and by other investigators la Germany and UX.
For comparison, concentrations of ssbsstos dust during brake maintenance reported by Cleklsh and Knight ^ shoved an average dally exposure of
0.68 f/sl (range 0.21 to 1.12) during brake service of 11 ears. During
truck brake service, the average vas 1;75 f/nli vith peak, during cleaning
of ths brake drum, of 7*09 f/sl*
.
Ths German investigation la 1973 ^ (now laeorporated la the Berufegenoeeenschafte: m
report *) reeoxded high concentrations* la ths brake asrviee departasat and
* 0.03 to 0.79 m^a^ aad vi^h background workshop atoosphere of 0.03 to 0.05
vhvre rc!.jn>nj v*s c'c-n1* without ibist extraction. Although Mfh
censentr^i'ons of f.nr.t vcre observed during blovin; out, no chr'EQtll*
e>str>s crnld be detected by infm-red p*ctrcr*tr7, end- the Individual
fibres which could bo detected optically could not be identified is
asbestos.
"
7be Cer*. * r 1 Tnv 1 mrr <* n t
Tur'nr tkr eyi-l'rati>n of i'ium br.V-es, di&c j>?c z>~ clutch fae'r.^c,
'
e.xll rit :os of f'O czr/Vce of the friction .v.trr-'sl sr von away.
These ualeriels contain between`50U to 6<v.` of *tb*sios, end it has beej .
sav-arsd by sons that thereby larje quantities of d*r.'erour esbestes curt
are beinj regularly discharged into the atnosphere. This, it i* argued,
creates dangerous atrosphrre a':In to tlt which hts produced olettos-
relsted A<erase (especially cancer) in sone working environments. "ire*
the estirwted coneuaption of ssbestos in friction r*te?ial is annually over dO,CO? tons 22 *for Europe and oyer 50,000 tens in the --cSA the novnis
Evolved =-ro substantial* An salinate carried out by the Fendix
Ccrpcrct'on with the support of the VS Civirosaeatel Freteeticn Agency (Z7A)
calculated that the anovnt of friction nisterial worn svey in brakes end clutches aiur'*lly in the USA it around f0,000 tons,1*' (of which 17,000 tons
'? the eslosios content i.e* 6<Y/. In FHirope the content of brake linings is nearer 505*). However it is clear free nsacurenenta nade at a number of locations with heavy road traffic that inslcslfieant quantities
2% 2A of 'os?lrblc ssbestos dat ere *? saltted*
*m * -fc* c.-st irportaat* faodOr in dispelling anxiety is that tha asbestos
content of the wear products of friction seterisl is not saltted into the stsosphers in the for.*, of respirable esboctor dust. lilted, a number of enbisnt sir investigations indlcats that it,is difficult novtdays to find asbestos fibres, in ary significant quantity, regardless of sise, in the
2i atnosphere - even in the vicinity of asbestos esnufaeturing plants*
Keasuxevents of the anblsn^sir even in heavy traffic conditions do not
show any significant level f
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confined tunnel cnvlronnsnt night be thoucJit to create the worst conditions, no significant build-up of asbestos dust he* been detected.^'
The explanation la simple and la confirmed by a niober of careful scientific investigations. The heat generated In the process of applying the brakes or the clutch (the reason in fact why asbestos is such s vital coaponent) la sufficient to destroy the original structure of the asbestoa fibre. From a temperature of 450C the chryaotile structure begins to convert to a non-crystalline amorphous phase, leading to a loss of stability of the fibre structure. The mechanical strain applied during the braking process has a pulverising and grinding effect, leading to disintegration of the fibre structure. The German report ^ calls it
"a kind of niero-milling so that the dust no longer contains any fibres".^
Froa e tesperature of 650C a new crystalline structure develops called
Forsterite, vhieh will be fully developed at temperatures of above 700C.
Generally, forsterite cannot ba traced in brake lining duata. This neens
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.e. m
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that temperatures beyond 65O C either do not occur or are only very short
lived. The decrease of tha chryaotile content, however, indicates that temperatures beyond 450C are reached because the amorphous phase of the
chxysotlle cannot be traced analytically (by either infra red-epectroeetrie
or X-ray dlffratcnatlc methods).
*
/ Examination of the rsaidut of wear products in brake druaa eonflzsa that the asbestos eontsnt Is usually leas than 1J of the residue.^ It has
^ been suggested that tha dust escaping Into anbient air nay contain s high er proportion of the fine respirable asbestos than dust left la the druse but
. ' careful studies designed to entrap this escaping portion of the vear . . product shov that tblo is not so. Various investigations into the amount of
..asbestos remaining In the residues froa friction processes have been carried
out vhieh indicate hov minute Is the fraction of asbestos released In the
application of fxiction. The latest report, from Germany, confirms that
technical lnvestlgatlone In recant years have repeatedly shown that the
duet generated by friction of the linings in use - as opposed to duet created
o
... ........-----------
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during the finishing and handling of new linings - ** rule contain* only tracee of free ehrysotile fibre, i.e. of the order of 1J4. The working party was unable to provide clearer Infra-red spectrographical evidence of ehrysotile. U*ider phase-contrast and electror.-nicroscopie scrutiny* the dust contained Just a few isolated fibres which could not even be definitely identified ac asbestos. This is consistent with the investigation by UK govemnent and industry investigations In 1969 ^27
vhleh reported that the fres asbestos content of wear products of drua 4-
brake lis<njs rarely exceeded 1$. 'J[l disc brakes ths content was even .
lover.)
4 'r
The Jendix'investigations for 1H0TE in USA in 1975 G*v* a rang* from
1.65J: to 0.003Jj - only three tests vers sbovs 1}S and the overall average
was 0.2&. This study also determined that only J.# of ths asbestos
content of all ths vaar products over the whole rang* of US motor vehicles became airborne -- estimated at $060 lbs. annually.^
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The Ford Kotor Company carried out study 28 based on dynamometer teats which shoved that during brake usage lass than 0.03' of ths lining wear was released in the fora of froo asbestos. Ths study estimated that concentrations of ssbsstos fibre in ths urban atmosphere la the US due to brake usage was less than 0.07 * 10~^ i/a? (.07 nanogrsos) (less than ons
Rillloath of ths 2 f/ml oocupational oontrol standard).
Itsasurs.^nts carried out at points of heavy traffic concentrations in' the *
UK by the Arbestoils Ssseareh Council* under the observation of ths TUC
Centenary Institute of Occupational Fsalth, also found no greater
concentration. Even In ths underground railway system, this surrey found the asbestos content to bo of ths ordor 10*" g/tP to 10"^ g/m\ (10 ags -
to 100 ngs/5)24
* .*
Finally, soas observations mad* within ths last thre* ytars by two salnsat occupational health experts, oa oocupational risks and risk* to the general
T
?0 Pr. John Gilson, ' rwii-vin* rnb'slos
on occupational ha?rd fn
Crnorrl group *n '''ich lie Include* friction natcrisls, cay* "Despite the thousands of products containing kcbeeto*, *-v-.rt.ee of ill effects from
lhair u!*e 1* very snail". T.t adds the qualification tint occupntiono
involving brake nhoa r.a.inicnunce have Veen shorn to l *t rich in th* pt*t.
'Although nest of the asbestos in brske 3hos J* de^radeiS, th* dust in ths
l r:'..e dror.s st<ll toniMns a r.r.%11 percental'* of ejbeatoa". 'Tre rajiitude
of the risk (of aelestosi* tn<i sei-othelloc* in there v-.r>ins regularly in
this e:
t) i* r.ot J.'novn but is likely to r *:_all." Profcnor
.".i ` in his report on public 'htflth risks, concludes "There is *
ev;/*53 cf no e>:rer.s :c:*k of nesothelin.:i from aibanics pollution vhic^*
hss exlr-ved in the ua-^'.bourhood of ckrysotile and arosits trines. Thsre i*
,.r.s .c-vifence of s risk to the general public at present". Lsier he repeat*
Ik*? v'?v in hir general conclusion "There 1* no established evidence
that, trve t.i.Vent *vjvosv:v, as prevalent in Vest cm 2uropS*n countries,
*t this raor.ont c-.niec such a definite risk; hemevsr, there exist too naay
v.r.cert*'ntica to > or.;- a;:;h a .ricv, though if th* rifk ws substantial it is
lively it r.r:*nip"?CiVj
ju < been detected V;* nov".
*
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Cere cea be as occupational health rich is the ranufsetur* of esbestos-
h** frietir* r*teri^ls. Rcvcvcr, experience he* choua that this is a very
V' '.\*i hjrlth r' r): and that it can b* ffactively controlled by veil tested
equipment and work procedures.
#
rt/n*:rds based on svrtcneiv* experience in the industry have l-een established
and equipment ic svaiisVla to naiataia these standards so that tbs
occupational health risk ran bo controlled, In fisay couatrJM thaao
stenforda are enforced by legislation* but in asy east trade and industry
have an obligation,. * vlth any occupational rafety problee, to inpleacat
the effaetlva fV
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JV'.f'.'ctt".
Proceedings of the International Conference on Pneunoconiosis
Johannesburg, S.Africa. 1969
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m * -v.V *of A *'.^3*r r ` Ir f.o i.vnro ?J (7 - e) ?CJ - ?:t C-v.ly *i7?.
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r.-'-u':n,l '._c:.:y f .-Research on Oivrr.
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Crorr, A.i, f^roer Ureelnr General, As-tf si or li.Iera*-t'i.--.l
Aaroefallen, London. "Prepress In Itc Control of Asht-rtos Iwrt
?.r Vic Vor^lnet'*. Ii>V j -ri: nz,l< C:r..V-:-r *t or. -ocMiierJ a,
Cavecet. To^tnVar 1?7?.
Gosran Pntesatlon of Iniastrisl lee'dent an* Safety Insurant*
Colorations' Z.T,
r-T*,*.ncv<*fi <n (^rn,*\r<ryxy).
research report - Achenlo*. "Invs stintless' Into Eealth IT*'JirAc
throng Dusta Vy BraVr#-HninrT* centslnln; Aabeatot*'. (Analytical
epidaaiolojioal and aninal. Investigations) HtGOthaz 1?76.
.
"Kyften* Standards of Airborne Asbestos Ihtct Concentration* for
MS* with the Aeb#ete
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)'<.<<. v Tnt K':<(' *i rf.fi "sl/il*
r-jr^s.*: r.:h 7*i*titu{e of
FeSfration of
Tcnfe Assoc'*ticns (?i'.jf*j*rioererifa>.?flf;n),
*?in, <Vr..r.y), and r r.dT:Vt (iVivnr'e.n Stale, Institute for
In.*)-, 'rirl "'fel;', '*?pch) "Taver ti^Vout i:i'-o t!ie r>rsrda
t;.* .1; *t of .'clr-5-*rs-contn'n'nc fi^sttrn lining*". J.ne 1575.
10.
CiPfcrir.re on "`vrnr.-re .? A'-V.^lce <Ju 'r.v
<<n<i Cluich
*r.re. Fr-nAv.-yid, L'. ^y, 2::.-]tr.n, :>.ch
e) I*e G.L: TrJtieh lijiend, LouJa-^f.j*, "irrsia^h-j!"., \
'T.-V'cvinj C.'sts frer; .Trfilra AwKi'jMt; farir.j Servieinj .Otcrr.etlv* Cltsninj !>thocs".
--
---
V) r?tch,D., ferouc, Ch?.pal-er.-l*-?r` th, Certyehrie, rcclani
.
*
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.
''Possible Altorafit. ves to Asbestcs r.r Friction ]>t*riel".
#
c) K.L. end Efe'irh, D.5., Keditsl S'i"'ic*s, 7crd ofTcJ tetri, !Ti*pritv-oofJ, Freer,
"Ir.vc-r.ti.?t?on.* *r.te. Alt*j$*.i2va 7its of Control'for'Ihst i/r-eratcfl C'ir'ng the Clc^ntR" of "re?: AsreiiblJrs ear*. BrJcs".
fi) rJc-:: sh, C.C., end-2a2iM, X.L,, (ss above) "j-poeure to Aebrttos dw<xs3 Tir.'-.e !Mivic-rmcen. *J2 Annuls of
-- Cos-pat i real Eyjiane. Vel.lJ 1J7C.
11.
* 12. 13.
Sentient M.L; Kinter, decide/ ton, Tor.'-.rhlr#, Ch.U.nd. Personal
eoK&unicatloa to A.A.Cross - Asbestos Casts - test durie* drua
. brake calntenan* ee. Kay 1974*
.
.
Cross, A.A.; Chaixnan, H.virercental Control^ Conj-.itVie, A3C . 2bri*ysi. "ielestoc Cast In TrJsticn F-ter'rlr". Peptcr.Ver 1975*
' . . /ecVo, CuChame, Saner*f ftendix Soxyo. and lijviron^estsl Trotertien `^ency, USA 'Brtks and Clutch Delation durinj Vehicle Operation''. Automobile Engineering Keeling, Detroit, Hthirta, USA Ksy 14-18 1973.
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*ylnrt 3=*t r>vf.il *o - r>ltv. of Ver':*w. (SYcpAftrY). 1?75.
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Ic*#sTit`t,.on2 Confcrcae* on Oec-patirTi?l Eolith, JSri^tca,
2c,lta3. r?j' atcr 1975.
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2d. .`rlrrtcj'is .-oaeerch Cornell,'Tr-ehr el e, Hi!~l*r.. Personal coc-Trorvication to A.A.Cross* "Investigation into levels of airborne asbestos dust in the London Underground, etc.". 1978.
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Jo; z,*-'Ivov< 11r} Senver, Colorrdo, USA. Tontor. :vV.f -
3rnk Liclsj* Caission 1977.
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Vinton Laboratories, Surrey, Inland.
no cause for elans".
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TuffJ.fcy, U.L., Ferodo, Chapcl-or.-lc-Trith,
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Feraonal Conr^ftiination - Asbestos Content of **enr Cr'-ircts fno
Friction Materials. June IJfJ.
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Anderson, Cealer, KeCune, Spry*; Ford Motor Cor^any, USA.
"Asbestos ZSissioaa froa Brake HjynaMpeter Tests". ($ef. as 13) e
Cileon, J.C.t fodner Director of Kedloal Researeh Council
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"t;ir.>r,.9 Institute. Pr.mru*, T'ov Jersey, VSA. October 1973.
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