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l'hAlNTIFF'S
ASUESTOS DUST DEPOSITION AND RETENTION , IN RATS
KXIIiniT KD-194
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.. ' J. C. Wegner and J. W. Skidmore '
.
Aferfieo/ Rr.ttarch Council, Pnaumoeoniocie Bcetarek Unit, Uandough Hotpilot, f'rnarth, Glamorgan, Great Britain
; - . . INTNODVCTWIN . t .
.
In previous animal dusting experiment) histologies.! studios have eatab-
.
llahed differences in the ffbrogenic properties of various types of asbestos
. .<*.i"' : *'
(Wagner, 1965 and elsewhere in this monograph!. Experiences with hu man cases of pleural mesothelioma have indicated that these have occurred mninly in association with (he Inhalation of crocidolilc, but in a current
research project the intrapleural inoculation of a variety of dusts -- ehry- ' .
stile, crocidolite, amosite, and silica -- into rets haa induced pleural
mesotheliomas. The amount of dust inoculated, 20 mg,, appeared by bia-
' tnlnpiral examination to be greatly in excess of the amount found in the
majority of human cases of pleural mesothelioma, '
.
in sn attempt to clarify the position a aeries of dusting experiments was
planned, and for this it was desirable to produce sn experiments! method
by which cgua) amounts of any asbestos dust could be deposited in the. lungs ft! rats by an inhalation method. Additionally it was necessary to ascertain
whether the various types of aahestoe were, retained in the lungs to the .
wtn* extent and had a similar histological distribution. With these objec-
'
lives a method was devised for producing the dust clouds and a preliminary . -
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Wfty-aaven male -and M female standard WiatarAlbino'Wla'Vert '-rifM* ftiif the' experfmenCand idveit weiit randon^^nocate^W aftnCatisticat
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'basis tipt* 6 *Toiipa,.Tour ttf'ttjs
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' fetuslsrst* were exposed to airborne eibuda of ehrysotJle,' erocidoiite, amt^. ' ' ^; j site, or powdered glass; the first group*waabot exposed to duit. and theV'^yii:': ttU staking up thta group were used as'eontroi*. The powdered glass was - " iintl.uded as an Inert nonflbrous duit for compsrative purpo**a.^:;*V!
' -,' jRhodtsian chryaotlle and South African erocidoUte and ''amosite were .\i
. '`bbtalnei'ln the most finely ground commercial grade, and each waa further ..vJSukV i microhammer mlll'to .break doyrh l
itlf^idbiejr
ground*
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Winner 4 Skidmorv: Deposition ami Retention in Rati tOO'
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DIAMETER U D l S MICRONS . t
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riituu t. 9iw iffertiwi characteristic of horizontal elutriator. ;i.-.
elutriator wm uaed. The design sise selective characteristic of the elutria-.. ' -'
tnr li shown in FIGURE 2. The free-falling apeed of a particle is dependent da it* site, shape, and density and is conveniently expressed in terms of the sphere of unit density having the same falling speed. Particles with falling speeds greater than that,'of a 7.1 micron unit density sphere would fall Impenetrate the elutriator and to were excluded from the collected
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y- vfSfcl ,VvV;rt|
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it* deposuad.yi
the Vacant cage compartment and s.ampled co. ntinuouaty during each '"^^?^;
jaher> Per jMja 'ftP0*01'*Pfr!.P4i A.f*wanples werealsoohUlnedln each inhalation
1ied)*WM ooSfSl
With' a tohfc "Running TvTmaV'ProcIpltator,'' Which Incorporate* * ,
. "iH her `was atihol
-'tbiRar elutriator. to determine the particle length distribution*/]
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K$i , s Duruffem o/ Btpoiwi\*i Surviit! '
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The rata were exposed to tha dust clouds for 7% hour* per day, on 4
.entretions'dfyil , 4fW of each week over a period of.6 week*. At the and of.each dayYex-.
usCinoluding^ 'ij*"*
"'r* tranaferi^'.from'^^^TO^I^W^.lhr^A^v* ^
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$000 0975 PRODUCED BY FORD
M
i&i
80 Annals New York Academy of Sciences
Wagner A S
were killed with chloroform. Similarly selected groups of rats were killed acre evaluated at U
2$ and 68 day* after the laat day of exposure.
' together with the st
.. L*nj> Itolotion and Analytit
to, Table 1. The le thermal Precipitato
Following the method of Mottura (personal communication), the track* jpithetrated the eloD
was tied off before opening the thorax and removing the lungs which wen' Ml prevent their p*
then fixed in normal saline. After four days a sagittal slice was taken froo ;;Four male and f
the left lung for histological examination. Both lungs, including all the 'ti, and 68 days aft
material except for three histological sections, were then available fortW determination of the dustoontent..
j'w'T.yt.he method pre'
it.'
*"* order of k mg. and since ail the types of asbestos contain appreciakk ta of splca, the lung alliea .content waa detebnined urihg'njidairC
'
`
: The rats were randomly`allocated .into the 5 groups, and each rat WM
fcbihce b^w^^^e^uif grbupe^'he four ihlutiatlon units were set op
.- and the dust cloud generators adjusted to give approximately the aunt ;-v* :'
, concentration a* measured by the Gravimetric Thermal Precipltstot (G.T.P.l. The'rata'were exposed for M daily duatlng sessions over a period
to*
of 6 weeks during which time 2 rats died of bronchiectasis. The samp)*
of total and respirable dust, obtained over the whole period of exposure
* **.
|.:sf-4
'1 I'I'X
t?
' .*!
,',J -
.'V DMuIaUt V**>:. r'ChryootU*
CrocldoUte
Amoalte
Total Duat , , ' 8td. Deviation
ee. . .
0.8
Jff.8 ' ' U.t
. 0.0 13.8
..,.1uptraW Duat 8td. Deviation. ` e.8 ,
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'-i.o 11.6
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PRODUCED BY FORD
Wayncr A Skidmore: Deposition mid Retention in ft*t#
were killad ,
we evaluated at I ho ahd of a*ch day. Tho a vamp* dual ouncfiniratione.
hifether with the standard deviation* aliout I ha tivrraft v#lua. aiv *ivn
lu TaiU.it 1. Tho k'liflh distribution* obtained from the bona Kunninf .e ^Whea';,., Thermal Precipitator sample* are ehuwn in nm/ar 8. Situ* all the particle*
fwhich war* ,'*{. '"'aken from
)e *11 the v
>VW for thf :V<
would
penetrated the elutriator it follow# that their free-fallint apeoda would aot prevent their penetration to the alveolar refiona of the luuf.
' Pour male and four female rata from each duat group were killed l.
Jt, and 68 daya after the laat day of exposure and their Junta extracted
by the method previoualy deacribed. Histological aectiona were obtained
irom the left lunf of each rat.
.
ipprtclabW ,
.
Histology .
'.
by a eoloii- '? Iculsted by. ;* V tb* dusts"'
Examination of the histological aectiona from the animals exposed to crocidolite and amosite dust showed similar features in the animals killed
acted from j formamide s$ croaeopieal
.eh nit was
o( ih< male
i sifniftcant ;.:a jvereaetujv^ ]='
1y the mw ;.. jvecipltator ij. .. . ,, ..ear a perfoi'j$
PRODUCED BY FORD
82
. .!> Annals New York Academy of Sciences .
' , Wagner
24 hour* after the final exposure. Recognizable fibers and dust partida made by first ar ' ' were observed in alveolar phagocytes thst were concentrated In the alveoli . .metrically. The
arising directly from the respiratory bronchioles. The majority of the content of the r fibers were within the phagocytes, bat the larger ones projected out from . silica content of
them. A few phagocytes were observed lying free in the large bronchiole*
and bronchi. '
. j. '
; .. '
.. Sections from the animals killed on the 29th and 68th day after exposure
showed the phagocytes In the same distribution with progressive organi
sation in the alveoli; some of the phagocytes bad fused to form giant cell*. .:
-' The silica eor airborne clouds -
40, 50. 51| and control rata eon small difference
' In the sections from the rats exposed to ehrysotlle and killed 24 boon ' . rate of the G.T.1 . v after exposure, phagocytes were seen In similar distribution to those pn-.
* viously described, hut instriking cohtrwrt oniy occajrional sTnsll fragment*; .'".usefully be ooin
of fiber were present, in these cells. In the rats killed 29 days after expo*urt; vof the rats kill*
these phagocytes had become large,'foamy, and vacyoltted/and only wy'- ^cumulative weif
. occasional fragxnents of fiber were mm. By tbs KStb day', although the'erJ
*Vfof the four dm
the'dust M^'j^ng'plugMytm''^^in^`M<^iona froro'tiie' rats klOed'
24 hours after the end of exposure was much more widespread. Phagocyte*. .v heavily Isden with dust were seen scattered through the airspace*. By the' ` , 29th day these phagocytes were mainly concentrated in the alveoli arising
*'frA'wt>> vifi,><*<'-'~i
Dust
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"` Lv%o butiAnalytU *'''' The quantitative .assessment of this weight of dust in the rat lungs wsi ; 'i1
-
bung c.t.p.
x
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Tasus 2.
exposure
sev/y-V,.' to.dust,..
fy * w.JyylV. tivH
:* SO
'li-r'i'fe-- 'Wm
Bex.
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^Weight of Dust la 'twijpf^
'i'btdi Brrw of mean. ChrysotUa brocidoUU , Amoalia;*:1
OltM
j,VYlungs of the
;:ib4n plotted
0.08 g 0.04 9.M X 0.8* 4.10*0.10 8.04 X O.U
.ra..t.s*., li,re,,spp*
0.58x0.19 1.5010.51 9J6 0.99 5.60jtO.M r ;*. irresalon line
0.99 a 0.0) 9.5410.00 9.99 x 0.97 8.80 x 0J0
0,97 x 0*15 S.tO^^OAl ,Mg 0.91 t.ioxo.ir
"glass, araoslte which are not The slope of ti
o.u i o.oa 1.18 X 0.91 9.98 10.89 8.80 a 1J7
O.tS x 0.09 1.V84 0,18 9.18 a 0.18 9.80 a 0.4*
,. ..The difference i ' .'al ths ond of
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PRODUCED BY FORD
Wagner & Skidmore: Imposition and Retention in Rats 83
dut*prtie)e ) in the alveoli ' %jftrity of the
hrfthchioie*
"Nter axpoaur* >ivt orrtnk' ;'; S m giant cett*Y.'.v illed 24 hour* i to those pre- ... nil fragments i'iitttf exposure ..'.and only very -/. bough the or- .' ' to crocidolite Vi
i . <
> i t distribution' `the rot* Willed 'd. Phagocyte*.' ,'.p*ce*. By the liWooli *rilng''
alveoli were filiation even
Ittsde by first ashing earb lung and determining the silica content eolori-
metrieally. The weight* of dust were calculated by reference to the silica
content of Ihe airborne dusts, similarly determined, after allowing for the
silica content of unexposed rat lungs'. The value* are presented in TABLE 2.
The silica content of the slie-selectad dust sample* collected from tb*
airborne cloud* of ehryeotile. crocidollte, amoalte, and powdered g)a* were
40, 50. tl, and 78 per cent, respectively, abd the hing* of the unexposed
. control rsts eonUloed 0.11 rag. silie* (range 0.05 - 0.16 rag.). There were
smell differences between tht airborne dust concentrations. The sampling
fate of the G.T.P. wa* 100 mt./min., which approximate* the minute volume
of the rat, and the net uptake of the dusta over the exposure period can
usefully be compared by expressing the weight of duet found in the lung*
of the rat* killed one day after the last exposure as a percentage of the
cumulative weight of dust collected by the G.T.P. The comparative uptake*
of the four duct* are shown in table S. Tht uptake of the chrysotile i*
only about one-third that of the crocidolite and amoalte; the uptake of the
powdered glass U twice as great.
.
..
'
Tabuc
.
. -.
Tut Umxr. or Purrs rx tiu Rat Luxes
' ` -Dust C.TJ\ mg.
Chrysotile 95.4
Crocldebu 91.9
AmosiU 41.1
Glass 49.4
'
tefl tinging. '
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jrat lungs >a*.i ^s**** `unV'^vif-fo
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m
.fikvg*
.If
Glass .Aii " djesr-*
'h.M'i'dJ t.WsO.MS
m
**f ^ilni'forehryadtfio'is -d-MI practically three'tlmee gmlsir^_
f lists'dUfi1nee;ln'WM! jstfffct U{**ke of thethrx* ubegtes
DM^`'and^of
posura "iSn^thoii' b* expuined'%jafereiioa
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PRODUCED BY FORD
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with deposition* by the site-select''
Thoroughly dii killed one day eft prepared by stir nltrocelluee in a trlbution* of the the powdered gt with projected t .amoslte ehsmbei
'microns tong W extracted from 1
Tkt differtnet T
/tract Ibpre^j regions. ' '
.
A method .-of ^Miltnsl Inhilntl
tb* dinits ` respirator/ bro tungs of the rs' ' but the subee< Weight* of dust ... collectedly th
nflbroui^dns 1 ? :ipper xeaplieuh ./'^ertieies to 'the .... otUe bu boen
trocl<MH* reduced fibrog elimination ra
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PRODUCED BY FORD
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Wapier & Rklilmurt': i>c|Ktat(i<iii mmI ftUiiiLi<iii in KnU W
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with depuallioit* of the Cut| iJiNvily rvlataJ lu the weight of dum cuJi<x-imj
by th* atse-solectiv* sampler.
Thoroughly dlapertisl Tnplo* of dust* Mlrorted from vK* luug< of ru
killed ono da,v after ojgtnourv and of the dusts tnllscled by the C T.I".' were
prepared by stirring k small amount of dual In a viscous aolution of bvi.
nftrocelluse In amyl acetate and examined microscopically. The sue dis
tributions of the dual extracted from the Jung* and the G.T.P. dust from
the powdered glass chamber were very similar, both containing particles .
With projected diameter* up to 10 microbe, but from the crocidolite and
amosite chamber* a marked difference wa* observed between the lung and
templed dusta. The duet from the aampler* contained fibers up to 250
micron* long but fiber* longer than 60 micron* could not be found in that
extracted from the lung*.
:
The tixe ejection of the horiiontal elutrietor take* no account of the' '
hape* of particles except in to far * they affect the free-falling apeed.'
The difference in the uptakes of the compact glass dust and of the fibrous
asbestos dust clearly indicates the higher efficiency of the upper respiratory'
tract is preventing the penetration of the longer fibers to the alveolar
region*.
: . ' .
. Discussion
A method of producing asbestos dust clouds ha* been deviaed and an animal inhalation ex|>erimeftt carried out to test It Observations on the Msiologica) distribution of the dusts in the lung* of the rata have shown that the dust* tend to accumulate in the alveoli arising directly from the respiratory bronchioles. The weight* of the asbeatoa duata found in. the lung* of the rata at the end of exposure were found to differ considerably, ' hut the subsequently determined elimination ratal indicated that, the ` weight* of duet deposited were in a constant ratio with,lbe weight* of duieV
WpS$mv<
1
iMS Pi
t&m
.''iMiioed librogenicity of this dual. The .reason'for the differeneein the
x tilmlnetioo rate remain* t
1*
mmm ' CmirtlCRt, J'.k f. V>\ flxtnuoa*. J9C4. The else dfstrtbotton'of duat retained & -.;j ?a
' f.j fa> th* tang* of rsu and duu collected by site selecting samplers. Aon.*',' .-.ivL"
iWihd mineral fluttaAnalyat M
90tO 0981 PRODUCED BY FORD
PRODUCED BY FORD