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T H E O C CU R RE N CE
O F
P L E U R A L C A L C IF IC A T IO N
A M O N G ASBESTOS I N S U L A T I O N W O R K E R S *
I r v i n g
J.
Selikoff
S e c t i o n on En u i r o n n i e n t a l H e a l t h
D e p a r t m w t
of Me d i c i n e
T h e
M o u n t Sinai
H o s p i t a l
N e i ~ ork L . Y .
Th e ea r l ie s t rep or t s of pu lm onary asbes tos is l in ica l , ana tom ica l ,
radiological ade no men tion of pleural ca lc if ica tion. We can now ap -
p re c ia te tha t th i s a b s e nc e o f c omme n t wa s no t ba s e d upon ina t t e n t ion o r
incom pleteness of observatio n. R ath er , th e asbestos is seen by Cooke, Wood,
Ha ddow, S te w a r t , S ims on , Lync h , E l lma n , Pa nc oa s t , Pe n de rg ra s s , Me re -
wether , was in some respec ts no t the sam e asbes tos is seen today . A resu l t
of exposure under much m ore unfavorab le condi t ions , th e pu lmo nary fi-
bros i s be ca me e x te ns ive a nd d i s a b l in g more ra p id ly , b r in g in g pa t i e n t s to
me d ic al a t t e n t ion a f t e r s ho r te r e xposu re s. Fe w e r ind iv idua l s we re a ble to
work fo r m a ny de ca de s in a s be s to s t r a de s . An o the r f a c to r wh ic h le d to
t h i n n i n g o u t of t h e r a n k s w a s t h e
large
num be r o f wome n a mo ng a s be s to s
te xt il e w orke rs , who l e f t work f o r home a nd w e re los t to indu s t r i a l s u rve y . '
S ince the re w e re , in a dd i t ion , ma ny fe w e r e mploye es in the s e t r a de s to start
with , the num ber reach ing a 20-year- f rom-onse t-o f-exposure po in t o f obser-
va t ion wa s smal l indeed . As we sha l l see f rom da ta p resen ted h ere , calci fi-
ca t ion i s usua lly no t seen un t i l th i s po in t i s reached . O ur p redecessors , who
ma de
so
ma ny im por ta n t c on t r ibu t ions to the prob le m
of
asbesto s is , could
no t ha ve ma de th i s one . I t wa s no t the re f o r the m to obs erve.
H i s
oricn evie
T h e first cases of asbestosis could not, as noted, have had pleural calcifi-
ca t ion . Montague M urr ay 's pa t i en t had a 14-year h is t o ry of asbes tos work
in 1900, and the re i s no record of m edica l exa m ina t ion s made of th e de a th s
in a n a s be sto s t e x ti l e f a c to ry re po r te d by Au r iba u l t in 190 6 ; the s e work -
people , in any case , d ied in m any ins tanc es a f t e r only five ye ar s of exposure . ''
Cooke 's pa t ien t , repor ted in 1924 ' and 1927: ( re po r ts which d id much t o
s t im u la te in te re s t in th i s p rob le m a nd p rov ided the na me f o r th e pne umo-
conios is )
;-
died a f t e r 20 yea rs of asbes tos tex t i le work . Po s tm orte m ex-
amina t ion showed the p leurae to be th ickened bu t ca lc i f ica t ion was no t
mentioned.
Ea r ly in the 1930 's , a num ber o f re fe rences can be fou nd to observa t ions
which may now be in te rpr e ted a s pe rhaps h av i ng been due to p leura l ca lc i -
fication. Sp ark s w rote of
. . .
some smal l ca lce reous depos i t s
.
.
.
seen
sca t te red in the lower zones o f approx im ate ly t h e same s ize
as
th e ca lc i fy -
*This study was supported
by
the Health Research Council of the
City
of
New York.
351
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352
A n n a l s N ew
York
Academy
of
Sciences
ing tuberc les , bu t they have a s l igh t ly le sse r dens i ty and
are
i r r e g u l a r i n
ou t line, ” bu t ma de no me n t ion of s pe cific p le u ra l c ha nge s . D ~ n n e l l y , ~oo,
obs erved c a lc if ic a tion , bu t in te rp r e te d i t a s be ing in the pa re nc hyma .
Gloyne” remarked on “horn- l ike” changes , bu t i t i s no t c lea r whe ther th is
re f e r r e d to bu rn i s he d th ic ke ne d p le u ra o r to c alci fi ca tion . Th e re i s no
mis ta k ing t h e des c r ip t ion of Lync h a nd S mi th , ” on th e o the r ha nd . The y
speak of the p leura be ing th ickened an d co llagenous and “pa r t ly ca lca reous .”
However , the impac t o f th is observa t ion was muff led by t h e m a i n i m p o r t
of the i r case repor t , which de ta i led the
first
case of asbesto s lung cancer.
S imi la r ly , the re was no spec ia l no te made of the observa t ion by Vig l ian i
of pleural ca lc if ica t ion, in his descr ipt ion of tw o autop sies w it h asbestos is
(1940 )
.lo
Pleura l ca lc i ficat ion was no t m ent ioned in th e severa l roen tgenograp hic
s tud ie s of pu lmona ry a s be s to s is ma de in the s e de ca de s. Th i s wa s th e c as e
i n t h e first eva lua t ion of X-ray chan ges am on g asbes tos worke rs , mad e by
Pancoas t an d h is co l leagues” in 1918 and in subsequent s tud ies ,’” ’“ in -
c lud ing the p ioneer desc r ip t ions
of
Wood.I5
t h i s
wa s t ru e eve n in the e x te ns ive s u rve ys ma de by Me re we the r (193 3 )
’?‘
n d
by Dreesse n and colleagues (1938)
?I i
Th e a bs e nce
of
c l in ica l re fe rence to
p leural ca lci ficat ion w as m irro red by
a
s im i la r h ia tu s in pa thologic al s tu d -
ies,
as
in th e ea r ly ca r e fu l ana tom ica l desc r ip t ions of th e d isease by Gloyne”
an d the la te r comm unica tion of Lynch an d Cannon .y7
Th e v i r tua l absence of rep or ts o f p leural ca lc if ica t ion wi t h asbes tos is
conformed wi t h the experience o f the in f requency
of
th is f ind ing in genera l ,
as att es ted by severa l early collected series ,“-:“’ in wh ich th e re la t ively f ew
c a s e s we re u s ual ly s e c onda ry to e mpye ma (pa r t i c u la r ly tube rcu lous ) ,
t r a um a a n d he motho ra x . T he re we re s c a t t e re d in s ta nc e s of “ id iopath ic ”
ca lc i f ica t ion , bu t s ince occupa t iona l h is to r ies were no t ava i lab le in these
cases, th is source w as no t cons idered .
T he quest ion of occupational du st s ca us in g pleural ca lc if ica tion became
muc h more im por ta n t , howe ve r, w i th the s t r i k in g re po r t of S ie ga l a n d h i s
colleagues:”-:” of t h e findin g of num ero us inst anc es of su ch calcification
d u r i n g X - r ay s t u d i e s of t a lc m i n e r s a n d m i l l er s in n o r t h e r n N e w Y o r k S t a t e .
The s e obs e rva tions a re of pa r t i c u la r in te re s t to us , s inc e the s e m e n w e re
exposed to t remol i te ,
a
v a r i e t y
of
asbes tos
;
th e p atholo gy of th e disease”:’,:’’
resembled th at of c lass ical asbesto s is , including th e f inding of “ ta lc bodies ,”
wh ic h a r e no t d i s t ing u i s ha b le f rom a s be s to s bod ies.”:
I n re t rospec t , t h e p leura l ca lc i ficat ion seen amo ng t remol i te ta lc w ork ers
may pe rhap s be considered a vari e ty of asbesto t ic ca lc if icat ion. How ever,
t h i s j u d g m e n t h a s a s a background th e deve lopment of knowledge concern-
in g th e occurrence of p leural ca lc i ficat ion i n asbes tos is an d th e c la r if icat ion
of th e va r ie d na tu re of “ t al c ”, s ome ta l c s c on ta in ing ove r 80 pe r c e n t
of
Clin ica l s tud ies a lso fa i led to cal l a t ten t ion to th is com pl icat ion
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Selikoff
: Pleural Calcification
t r e mo l i te a nd o the r s ha v ing t r a c e s o r none. ’I’ Th is c l a r i ty o f r e t ro spe c t ive
vis ion was less evident at the t ime of the repor t o f A.
R.
S m i t h i n 1952,
when s he found roen tgenograph ic ev idence of p leura l ca lc i ficat ion in 14
of 221 t remol i te ta lc workers 6.3 pe r c e n t ) , bu t in none of
261
asbes tos
workers:” T he obser vation of isolated cases of calcification am on g bak elite
in s u la t ion a nd c a lc imine worke rs wa s a s c r ibe d to the f a c t tha t bo th t a l c
a nd mica a r e us ed in the i r ma nu fa c tu r e . As l a t e
as
1955, s tud ies of bo th
pa tho log ica l and roen tgenolog ica l f ind ings in asbes tos is fa i led to ca l l a t t en -
tion to pleural calcification:’*-’”
I n 1955, in te res t w as a t t ra c te d to th e occurrence of p leura l ca lc if ica t ion
in asbes tos is by th e inc lus ion of t h i s e n t i t y i n a l is t of roentgenological com-
pl icat ions of asbes tos is observed by Jaco b and B ohl ig in th e i r s tu dy
of
343
Dresden asbes tos work ers . ‘ Th ey fou nd such ca lc i ficat ion in approx im ate ly
five per c ent of t he ir cases .
N o
d a t a w a s r e p o r te d c o n ce r n in g t h e d u r a t i o n
of exposure
of
the employees s tud ied .
A
va luab le inves t iga t ion was
pub-
l i s he d the ne x t ye a r by F ros t , Ge o rg a nd Ma l le r , de s c r ib ing 11 cases of
calc if ica t ion among
31
a s b es to s w o r k e r s w i t h m o r e t h a n 20 ye ar s of work
exper ience .44 F eh re rep or ted seven cases o f p leura l ca lc i ficat ion am on g 35
employees in a fac to ry m aki ng a composi tion mat e r ia l (“S te inholz” ) which
c on ta ine d t al c (b u t wh ic h a l so wa s ma de w i th a s be s to s du r in g the pe r iod
in which the men w ere exposed) .“ S ince then , add i t iona l examples have
been recorded,’” i‘’ and t h e use of p leura l ca lci f ica t ion a s a m a r k e r t o d i s -
cover cases of asbes tos is ha s been br i l l ian t ly dem ons t ra ted .” Pa re n t he t -
ical ly , such d i f fe ren t ia l d iagnos t ic use h as been ve ry va luab le in ou r hand s
and pleural ca lc if ica t ion is of ten a re l iab le and accura te index of p rev ious
asbes tos exposure . App rec ia t ion of such d iagno s t ic re liab i l i ty wi ll m ake
fo r inc re a s e d a c c u ra c y in the r a d io log ic a l de te rmina t ion o f the p re s e nc e
or absence of asbes tos is , a problem which has been bu t incomple te ly re -
s olve d wi th ou t th e u s e
of
th is sign.’?
P r e s e n t I n v e s t i g a ti o n
This r e v ie w
of
p e r t i n e n t r e p o r te d l i t e r a t u r e d e m o n s t r a t e s t h a t p l e u r al
ca lc i ficat ion was no t observed in assoc ia t ion w i th asbes tos is un t i l sca t te re d
e xa mple s we re s e e n in the
1930s.
In th e pa s t de c a de, m a ny m ore c a s e s ha ve
been repor ted , wi th much wider apprec ia t ion of th e im po r tan t assoc ia t ion
of
th e tw o condi t ions . Above ,
t he hypo t l i e s i s was proposed that t h i s
se-
quence of e ven t s i s t h e
r 3siilt
of t h e l i m i t e d e x t e n t
of
t h e n s b e s to s i n d u s t r y
b e f o r e 1 9 1 0 i t s expan s i on 1910-1930 and l a t e r
i d
t h e c o n c o m i t a n t n e c e s -
s i t y f o r t h e l a p se o f a c o n si de r a bl e t i m e - u s u a l l y m o r e t h a n 20 y e a r s -
b e t w e e n h u m a n e x p o s ur e t o a sb e s t os a n d t h e radio log ica l appearance
of
pleural calci f icat ion. I f
t h i s
h y p o t h e s i s i s c o r w c t t h en p leura l ca lc if i cat ion
should be seen ioitli i n c re a s i ng f r e q u e n c y in t h e f u t u r e .
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354
Annals New
York
Academy of Sciences
W ith reg ard to th e expansion of t he asbes tos indust ry , i t may be no ted
that asbes tos product ion began on a commercial scale in 1876 ( I t a l y )
1878 ( C an ad a )
.5s
Fro m then to the end of 1909, the to ta l wor ld product ion
was l ess than
700,000
tons:” F r o m
1910
t o
1929,
world product ion was
seven t imes tha t amoun t
4,123,780
t o n s )
54
Ou r s tud ies in th is inves t igat ion were des igned to provide da ta concern-
in g th e second fa ct or apsed t ime f ro m onset of exposure nd a lso to
demonstrate the incidence of pleural calcif icat ion at least in one type of
asbestos work , in order to c lar i fy i t s appl icab i li ty as a diagnost ic radiolog-
ical sign.
Mater ia l s nd Meth ods
O ur s tud y has been concerned w i th 1,258 cu r ren t mem bers of t he In t e r -
nat ional Associa tion of H ea t and F ro st Insu la to rs and Asbestos W orkers
in the New York-New Je rse y Metropoli tan area . Detai l s of th e procedures
ut il ized in th is in vest iga t ion have been recorded.55 Briefly , these m en rep-
resen ted a l l l iv ing members of the insu la t ion workers un ion in th is area
who had been on the union’s
rolls
Dec. 31, 1942
or
who had joined at any
t i m e b et ween J an u a r y 1, 1943 to December 31, 1962. O n J a n u a r y 1, 1963,
1,086 were act ive work ing members , 63 we re re t i red (pr im ar i ly because
o f age) ,
34
were no t work ing because of i l lness and
75
h ad w i t h d r aw n f r o m
the insulat ion union, to take o the r work. One thousa nd one hund red seven-
teen of the 1,258 members were examined , includ ing 984 of the work ing
members , 50 of those ret i red, 28 of the il l and 55 of those otherwise em-
ployed. TABLE deta i l s these da ta . TABLE contains a n analys is of t he men
s ta tu s
Retired
Ill
Withdrawn
Working
Total
T A B L E
ASBESTOSW O R KE R S N I O N
N.Y.
.J. 1943-1962. 632 M E M E R SD E C E M B E R
31, 1942. 890 A D M I T T E DA N U A R Y, 1943
TO
D E C E M B E R1, 1962.
STATUS
OF
MEN
E X A M I N E DU R I N GURVEY 1963-1964
No. Examined Examined
63 50 79.3
34 28 82.4
75 55 76.4
1,086 984 90.6
1,258 1,117 89.9
Status Jan uary 1,
1964 (1,522
members )
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Selikoff Pl eu ra l Calcification
355
Onset of exposure
50+
(yrs . )
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
TABLE2
WORKE X P O S U R E
I
E X A M I N A T I O NF
ASBESTOS
N S U L A T I O N W O R K E R S: A N A L Y S I S
Y
O N S E T OF
No.
Examined
36 28
41 39
64 54
92 83
126 111
18 16
66 61
186 174
225 205
184 154
220 192
Total 1,258
1,117
accord ing to lapsed t im e f rom ons e t o f employment (a nd indu s t r ia l expos-
ure).
I t will be s e en th a t
a
ma jo r i t y of me n in e a ch e la ps e d -t ime c a te go ry
wa s e xa mined .
The presence or absence of pleural ca lc if ica t ion
was
d e t e r m i n e d r o e n t -
genographica l ly . In each case,
a
s t a nda rd pos te roa n te r io r f i lm wa s t a ke n ,
u s i n g
a
200
MA,
fou r -va lve a ppa ra tu s w i th a
2
mm. ro ta t ing a node foc a l
spo t . Genera l ly , 10 MAS wa s u s e d wi th k i lovo l t a ge s va ry ing f rom 60-80
KV, depending on thickness of chest . N o gr id wa s u s e d .
I n a d d i t i o n ,
a
s ec ond , s ome wha t more p e ne t ra t in g film w a s t a ke n in th e pos te roa n te r io r
pro jec t ion in each case, to be t te r dem ons t ra te p leura l ca lci f ica t ion , e spe-
cia l ly in those ins tances in which pleural f ibros is coexis ted
or
whe n the
calc if ica t ion was located in such areas as t he poste r io r d ia p h ra gm a t ic s u l -
cus , beh ind the he ar t , in t he me dias t ina l p leura , etc .
In each case , films i n bo th a n te r io r ob l ique pos i t ions we re a l s o t a ke n ,
ag a in wi th the ob ject o f be t t e r dem on s t r a t i ng p leura l calc if ica t ion . Some
cases of such calc if ica t ion wil l be missed if routine oblique f i lms are not
taken . W e have been ab le to de m on s t r a te p leura l calc if icat ion w i th t h is
t e c hn ique when i t wa s obs cu re d in the po s te roa n te r io r f ilm by r ib m a rk i ngs ,
c a rd ia c s ha dow, d ia ph ra gm , me d ia s t inu m, e tc . Th e p le u ral loca tion of t h e
calc if ied p laques can o f ten be bes t dem ons t ra ted by t h is pos i t ion s ince in
the pos te roa n te r io r f i lm , the p la que s ma y a ppe a r b roa ds ide -on , w i th a n
i r re gu la r inde te rmina te ou t l ine , ye t a re s e e n t a nge n t i a l ly in the ob l ique
film as clearly pleural in locat ion.
Th e observa t ions made in th is inves t iga tion a r e based upon th e use of
the a bove X- ra y t e c hn ique s . I t would be a n t i c ipa te d th a t a s ma ll e r num be r
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356 Annals New York Academy
of
Sciences
of instances of calcification would be found in
a
s u rve y wh ic h fa i l e d to
u t i lize bo th h ig he r k i lovo ltage and ob l ique-pos it ion techn iques . Addi t iona l
roen tgenolog ica l techn iques may be used to fu r the r re f ine the d iagnos t ic
sea rch and would perhaps s l igh t ly inc rease the survey y ie ld , bu t we have
no da ta on rou t ine use of the se techn iques , which inc lude tomo graphy , t he
la te ra l pos it ion a nd t h e u se o f th e Buc ky d ia ph ra gm , a l tho ugh we ha ve u s ed
each of these with good results in se lected cases e lsewhere .
Incidence
of
Calcification
Roentgenological evidence of pleural ca lc if ica t ion is common among the
asbes tos insu la t ion workers . P leura l ca lc i ficat ion w as found in 150 of the
1,117 men examined . The re i s no o the r c ond i t ion now known in wh ic h
such a n incidence of pleural ca lc if ica t ion ha s been rep orted . Ne verth eless ,
the s e f igu re s ha ve l imi te d m e a n in g wi tho u t r e l a t ion to th e work e xpe r ie nc e
Onset of
exposure (Yrs . )
40+
30-39
20-29
10- 9
0
Totals
TABLE3
PLEURAL ALCIFICATIONM O N G ASBESTOS NS UL AT IO N ORKERS
Extent
of
Norm al Calc if ica t ion calc if ica t ion (grade)
o.
1
2 3
121 42.1
57.9 37 20 13
194
65.4
34.5 46
15
6
77
89.6
10.4
0
0
379 98.9
1.1
5
0 0
346 100.0
0 0
0 0
0
1,117 96 35 19
I
of t he men examined . Such an ana lys is is con ta ined in
TABLE 3 ,
d e t a i l i n g
th e incidence of pleural ca lc if ica t ion in re la t ion to th e lapsed period fr om
ons e t of e xpos u re a m ong th e me n e xa mine d . I t w ill be se e n th a t a mong
these men ,
all
with th e sam e type of exposure to asbes tos , ca lci ficat ion w as
re la t ive ly uncommon in less than
20
ye a rs f ro m onse t of e xpos u re . Thu s ,
we found no ins tance of pleural ca lc if ica t ion among
346
men whose expos-
ure began less th an
10
ye a rs f ro m the da te of th e i r e xa mina t ion a nd in on ly
five cases of
379
whos e e xpos u re ha d be gun f rom
10
t o
19
y e a r s p r i o r t o
the i r e xa mina t ion . On the o the r ha nd , a m ong men whos e work e xper ie nc e
ha d be gun more tha n
20 yea rs be fore , ca lci ficat ion was common. E ig h t of
77
w i t h 20 t o
29
years from onset of exposure showed calc if ica t ion, while
67
of
194
whose exposure had begun
30
t o
39
ye a rs be fo re a nd
7 0
of
121
wi th
40
yea rs o r mo re f ro m onse t o f exposure showed ca lci f ica tion.
No t only did the incidence of ca lc if ica tion inc rease fol lowing th e 20-years-
f rom-f i rs t -exposure -po in t , bu t the ex ten t
of
calc if ica t ion s imilarly became
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Selikoff : Pleural Calcification 357
~~ ~
0 24
g r e a t e r . T h u s , i n t h e
13
c a se s foun d in the g rou p o f me n w i th l e ss tha n
30
ye ars f r om onse t of exposure , the e x te n t of ca lc if ica t ion was l imi ted in
e ac h . On the o the r ha nd , a mo ng the 70 me n w i th c a lc if ic a tion in t h e
40
year-and-over g roup , a lmos t ha l f had ex tens ive ca lc i f ica t ion (Grade
I1
or
111).
It
is difficult
t o
separa te the e f fec t o f ac tua l years o f work exposure
f r o m l a p s e d t i m e f r o m first e xpos u re , s inc e in ma ny in s ta nc e s the two
f igu res c oinc ide , a m ong the m e n e xa mine d . To p rope rly s tu dy th i s que s -
t ion , i t would be necessa ry t o observe a s ign i f ican t num ber o f men w hose
work e xpos u re ha d c e a s e d ma ny ye a r s be fo re bu t ha d re ma ine d unde r
observa tion . Never the less , ana lys is of th e w ork exper ience of th e g r ou p
s tud ie d he re p rov ide s s ome da ta wh ic h would s ugg e s t tha t bo th fa c to r s
lapsed t ime s ince first exposure and to ta l yea rs of exp osu re - a re o f im-
po r ta nc e, w i t h the l a t t e r o f s ome wha t g re a te r c ons equenc e. Th us , we ha ve
a nalyz ed the f ind ings ob ta ine d d u r in g the e xa m ina t ion of
331
me n whos e
e xpos u re be ga n more tha n
25
ye a rs p r io r to th e i r e xa mina t ion . We d iv ide d
t h i s g r o u p i n t w o , t h e f i r st c o n t a i n i n g 54 me n who ha d l e s s tha n
25
y e a r s
of exposure du r i ng the i r pe r iod of employm ent and th e second cons is t ing
of
277
men whose to ta l pe r iod of work expo sure approx imated th e lapsed
25-50 Total
T A B L E
P L E U R A L C A L C I F I C A T I O N A M O N G
ASBESTOS
N S U L A T I O N W O R K E R S
E X A M I N A T I O NF
331
MEN W H O S E ExPost'itE
B E G A N
T LEAST 5 Y E A R S
BEFORE SURVEY
Ye a rs of Exposure
i
t
i
i
rade 1
Gra de 2
Gra de
3
t ime f r om onse t of exp osure .
As
can be seen in
TABLE 4,
of t h e
54
m e n
whose to ta l e xposu re te nde d to be me a s u ra b ly l e ss tha n th e per iod du r in g
which t h i s exposure occurred , on ly
11
ha d ple ural ca lc if ica t ion, an d each of
these
11
wa s min ima l in e x te n t . On the o the r ha nd , o f thos e me n whos e
to ta l exposure tended t o co inc ide wi th t he pe r iod in which i t occurred , th e r e
we re
127
ins tanc es of ca lc ifica tion am on g th e
277
examined . Not on ly was
the inc idence of ca lc i f ica t ion la rger in th is g roup , bu t the ex ten t
of
t h e
ca lc i f ica t ion was a lso g rea te r , approx imate ly two-f i f ths hav ing ex tens ive
f
E i c Y E i Y o n
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15-19
3/123
1/39
0/7
0/5
4/174
TABLE
PLEURALALCIFICATION*M O N G ASBESTOS
NSULATION
WORKERS
E X A M I N A T I O N
F
839 MEN WITH 0-24 YEARS WORK EXPOSURE;
ANALYS I S
Y YEARS SINCE ONSET
OF
EXPOSURE
10-14 5 -9 0 -4
Total
10/5
1
9/17 1
1/161 3/209
0/41 0/135 1/18?
0/3 0/19 0/192 0/2 21
1/205 0/154 0/192 23/83 9
Exposure
Onset of exposure (yrs.)
(Yrs.)
40-50+ 30-39 20-2 9
20-24
15-19
10-
14
5-9
0 -4
2/3
0/0
0/2
0 / 1
o/o
3/17 5/31
4/13 2/35
0/3 1/4
1/2
0/1
0/1 0/1
2 /6 8 /36 8 / 72
10/42 12/246
1 /551
40+
30-39
20-29
10- 19
0 - 9
calcif icat ion. These data would suggest that the total amount of exposure
is of c onsiderable importance.
We have also analyzed, in TABLE 5, the findings in 839 men wi th less
t h a n 25 year s of work exposure accord ing to the durat ion of years d ur in g
which this l imited exposure occurred. There were 23 instances of calcifi-
ca tion ( a ll lim it ed in e x te n t ) a mong these 839 men with 0-24 year s work
exposure. Twenty- two of th e 23 occurred in the group in which exposure
began a t l eas t 15 years before . There were on ly 13 instances of pleural
calcif ication am ong men w hose total work exposure w as less tha n 20 years .
Of these,
all
except one had begun the i r exposure
at
least
15
years before .
Looked a t ano ther way , t he re were
725
men whose work exposure began
121 28 65 70
194 96 62 67
77 47 25
8
37 9 340 36 5
346 342 4 0
T AB L E
ROENTGENOGRAPHICVIDENCEF PLEURAL
B N O R M A L I T Y
M O N G
1,117 ASBESTOSNStfL.4TlON WORKERS
Abnormal pleura
ibrosis Calcification
Years
f rom
I Number I Ny
nset
of
exposure examined
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359
Grade of
pleural
f ib ros is
0
1
2
3
Tota ls
??J
G rad e of pl eur al calcifica tion
0
1
2 3
No.
Calc.
240 171
45
17
7 28.8
99 61
25
11
2 38.3
43
15 18 4 6 65.1
10
0 3
3
4
100.0
3 2 247 91 35 19
l e s s tha n 20 ye a r s f rom t he d a te of the i r e xa mina t ion . On ly five ha d
evidence of calcification
(TABLE
3 ) . O n t h e o t h e r h a n d , t h e r e w e r e 22 m e n
whose to ta l work exper ience was less than 20 y e a r s , b u t h a d b e g u n t h a t
work exper ience a t leas t 30 years before . Five had calc if ica t ion.
Relation to parenc/ry mal and p le i r i a l
f ibrosis.
It
i s ev i de n t f r o m
TABLE
6
a nd
TABLE 7
tha t p leura l ca lc i f ica t ion may be roen tgenographica l ly
as-
soc ia ted wi th p leura l f ib ros is , bu t no t in a l l cases . The da ta in
T A B L E 6
s ugg e s t th a t p leu ra l f ibro si s a ppe a rs e a r l i e r th a n does c alci fi ca tion . Am ong
802 men X -rayed , a t a po in t le ss th an
30
ye a rs f rom ons e t o f e xpos u re ,
the re we re 13 ins tances of ca lc if ica t ion and 6 5 of pleural fibrosis .
On th e o th er hand , f ib ros is an d ca lci ficat ion of t he p leura do no t neces -
sa r i ly co inc ide roen tgenographica l ly in each case . I t m ay be th a t pa tho-
genetical ly calc if ica t ion ap pe ar s on
a
background of pleura l fibros is
;
s t u d i e s
in th is regard would be va luab le . Never the less , we have seen numerous
ins tances of pleural ca lc if ica t ion in the absence of roentgenographical ly
demons t rab le f ib ros is . As can be seen in
TABLE 7,
a m o n g 392 m e n w i t h a t
leas t 20 y e a r s f r o m o n s et of e xpos u re , the re we re 240 who had no roen tgeno-
graphic evidence of pleural f ibros is . Yet , 69 28.8 pe r c e n t ) s howe d s ome
calcification, 24 having extensive calc if ica t ion. However,
all
10 of t h o s e
with very extensive pleural f ibros is a lso had pleural ca lc if ica t ion, usually
e x te ns ive . I t wa s e v ide n t tha t
as
pleural f ibros is v is ibly increased, the
tendency to coincident ca lc if ica tion s imu ltaneo usly increased.
Ana lyz ing the 392 men wi th
at
least 20 ye a rs f rom ons e t o f e xpos u re
(TABLE
8 ) ,
of 292 wi th min ima l
or
no parenchymal f ib ros is seen on X-ray ,
t h e r e w e r e 98 with ca lc i f ica t ion . Among the 100 men wi th ex tens ive pa-
renchymal f ib ros is , the re were 47 w ith pleural ca lc if icat ion. Miil ler'G h as
a lso commented upon the g rea te r inc idence of p leura l ca lc i f ica t ion in in -
d iv idua ls w i th ex tens ive pu lmonary asbes tos is f ib rosis , f ind ing s ix pe r cen t
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Grade of
parenchymal
f i b r o s i s
0
1
2
3
Totals
TABLE
392 ASBESTOSNSULATIONWORKERS
I T H
AT LEAST20
Y E A R S
ROM ONSET
CORRELATION
OF
PLElJRAL CALCIFICATION
W I T H
PARENCHYMAL
FIBROSIS
N
O F
EXPOSITRE
Gra de of pleural ca lc if ica t ion
No.
Calc.
0 1 2
56
52 4 0
0
7.1
236 142 58 24 12 39.8
7a
38
23 11 6 51.3
22
15
6
0
1
31.8
392 247 91 35 19
calc if ica t ion in Grade I a s be s to s i s a nd
38
per cen t in G rad e I11 asbes tos is .
Suc h c ompa ri sons ha ve l i t tl e m e a n ing , howe ve r , w i th ou t r e fe re nc e to d u ra -
t ion of exp osure and lapsed t im e f ro m onse t of exposure , s ince G rad e
I
asbes tos is fo l lowing re la t ive ly shor t pe r iods o f exposure ,
as
can be seen
fr om o ur da ta above , cou ld be an t ic ipa ted to have a much lower inc idence
of ca lc i f ica t ion than the same grade of asbes tos is fo l lowing
a
long period
of exposure . I t i s w or t hy of no te t h a t ex tens ive pu lmonary asbes tos is may
exis t wi thout ca lc i f ica t ion
( 5 3
of 100 m e n i n TABLE 8) . I n c o n t r a s t , w e
fou nd fo ur ins tances o f ca lc i ficat ion (a lbe i t m in im al) a m on g
56
asbes tos
insu la t ion workers in th is g roup who had no ev idence of pa renchymal
fibrosis .
Bi la te ra l ca lc i f ica t ion . In approx imate ly ha l f the cases
(TABLE 9)
t h e
pleural ca lc if ica t ion was bi la tera l . In 49 c a s e s , i t wa s p re s e n t on ly in the
le f t he mi tho ra x a nd in 28 in the r i gh t a lone. Whe n b i l a t era l , i t wa s o f t e n
b i la te ra l ly symmetr ica l o r at leas t equa l in ex te n t on bo th s ides . However ,
in 2 8 cases one or t h e o t h e r s i d e w a s d o m i n a n t. Just
as
t h e l e f t s i d e w a s
mo re f requent ly involved i n un i la te ra l cases (49
as
c o m p ar ed t o 2 8 i n t h e
r i g h t h e m i t h o r a x ) , i n t h e a s y m m e t r ic a l b i l a te r al c as es , t h e l e f t h e m i t h o r a x
had ca lc if ica tion of g r ea te r e x te n t in
18.
It
will be noted in TABLE 9 tha t the more ex tens ive ca lc i f ica t ion tended
to be b i la te ra l . For ty -e igh t o f the
54
ins tances of extensive calc if ica t ion
were b i la te ra l , whereas on ly
25
of the
96
ins tances
of
l im ited calc if icat ion
had evident bi la tera l ca lc if ica t ion.
Localizat ion and a ppe a ra nc e . A l though the ma in bu rde n o f th i s c om-
munica t ion i s concerned wi th the inc idence of p leura l ca lc i f ica t ion among
asbes tos insu la t ion w orkers , i t m ay be of some va lue to b rie fly ou t l ine th e
roe n tge nogra ph ic a ppe a ra nce s . Th e re wa s no po rt ion of th e p le u ra foun d
i m m u n e
to
t h i s c omplica t ion . W hi le d ia ph ra gm a t ic p le u ra w a s a ve ry c om-
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Left
Right
Bi la te ra l*
Totals
TABLE
LOCATION OF P L E U R A L C A L C IF I CA T IO N I N
150
I N S T A N C E S
O F
SIJ CH
CALCIFICATION AMONG
ASBESTOS
N S U L A T I O N W O R K E R S
45 4
0 49
26 2
0 28
25 29
19 73
96 35 19 150
361
Location Grade of calc if ica t ion Total
1 1 1 2 1 3 1
mon s i t e , the c os ta l a re a s w e re f r e que n t ly found t o be invo lve d as w e r e t h e
va r ious po r t ions of t h e me d ia st ina l p le u ra . He re , th e per i c a rd ia l s u r f a c e
wa s no t in f re que n t ly invo lve d , pa r t i c u la r ly a long the l e f t c a rd ia c bo rde r .
The r igh t ca rd iac border was much less f requent ly seen to have ca lc i f ica -
t ion a l though the super impos i t ion of ve r tebrd l and heavy vascu la r mark-
ings ma ke a n y s t a t e m e n t w i th r e g a rd to th e r e la t ive f r e que nc y of pe r i -
ca rd ia l ca lc i f ica t ions on e i the r s ide hazardous . Ca lc i f ica t ions a long the
p leu ra c ove r ing th e a o r t i c knob w e re s e e n ; in s uc h in s ta nc e s , d if f e ren t i a tion
fr om calcified a or t ic plaques so me tim es was difficult . The fr eq ue nc y of
an te r io r medias t ina l p leura l ca lc i fica t ions w as low bu t , aga in , techn ica l
fa c to r s s uc h as super imp os i t ion of s te rn a l shadow s may have been re -
spons ible. Ca lci f ica tion in th is la t te r s i te w hen seen on la te ra l f ilms i s o f t en
ex tensive , an observa t ion which corre la tes we ll w i th th e known p a thways
of lympha t i c d ra in a g e f ro m th e pa r i e t a l p leura.:7 Whi le i t i s t ru e th a t the
lower por t ions of t he hem ithoraces b ear th e b r un t of t h e ca lc i fica t ion , th e
uppe r lun g f ie ld s a r e by no m eans spared . T he th ick , she l l- l ike ca lc if ica tions
a s soc ia ted w i th tube rc u lous e mpye ma a r e no t s e e n , a l thou gh t a nge n t i a l
ob lique views m a y s om e t ime s g ive th i s a ppe a ra nce . On the o th e r ha nd , the
ex tens ive ca lc i ficat ions a re o f t en racemic and lace - like on th e cos ta l p leura .
T h e y a r e d e n s er a n d m o r e b u r ni sh e d o n t h e d i a p h r a g m , w h e r e t h e y o f t e n
fol low the con tours of t he d ia ph rag m on the pos te roan te r io r p ro ject ion .
Oc c as ional ly , s ma l l “ bu t to ns ” a r e s e e n , w i th a rad io lucen t cen te r . Some-
t im es th e ca lc i ficat ion i s
so
ex tens ive
as
t o v i r tual ly obs cu re the pu lmona ry
parenchym a. On o th er occasions , it ma y invo lve th e p le u ra o f a n in te r lob a r
f is su re a nd in s uc h c as e s ma y ou t l ine e i th e r the g re a te r
or
l e s s e r in te r loba r
f is sures. On tom ographic s tu d ie s , we have fou nd smal l l inea r a re as o f
c alci fi ca tion wi th in th ic k a re a s of p le u ral f ib ro si s , t he l a t t e r in t he f o r m
of pleural scal lops . Our experience with seria l observations of pleural ca l-
c i f ica t ion a re too l imi ted to more than sugges t tha t ca lc i f ica t ion does no t
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appear , in ex tens ive cases , s imul taneous ly in a l l a reas , s ince we have ob-
se rved ex tens ion of ex is t ing a re as as well
as
increasing density of calcifi-
c a t ion o f e x i s t ing , f a in t a re a s .
Discussion
Evidence now available indicates
that
th e p leura l ca lc i ficat ions seen w i th
asbes tos is invo lves th e pa r ie ta l p leura . Never the less , such ev idence i s no t
ye t ex tens ive and ou r observa t ion of ad mit ted ly in f req uen t ca lc i ficat ion in
the in te r lo ba r f is s ure s ugg e s t th a t th e v i s c era l p le u ra m a y oc ca siona lly be
involved a s well. Th is would co inc ide wi th t h e known fa c t th a t whi le t h e
pa r i e t a l p le u ra
is
most heavily involved by f ibros is in cases of pulmonary
asbes tos is , t h e v isce ra l p leura m ay a lso be found to be th ickened . I n ou r
c a se s , ra d iog ra ph ic s tud ie s a r e c ons i st e n t w i th thos e of o the r s in de mon-
s t r a t i ng tha t , by a n d l a rge , th e c alci fi ca tion s e e n is i n th e pa r i e ta l p le u ra .
Th us , t a nge n t i a l v iews s howe d l i t t le
or
no so ft t is su e between th e calcifica-
t ion a nd th e c he s t wal l a nd c ine - ra d iog ra ph ic s tud ie s showed th a t th e lung
moved independent ly o f th e cos ta l p leura l ca lc i ficat ions , w her eas th e la t te r
moved synchronous ly w i th th e r ibs an d ches t wa l l. Kiv iluo to“ dem ons t ra ted
th e pa r ie t a l loca tion of t he ca lc i ficat ion by d iagnos t ic pneumothorax .
Th e d iagnos t ic imp or tance o f th e presence of bilateral pleur al ca lc if ica-
t ions has been emphasized by Jacob and Bohlig‘” and Kiviluoto.”’ Muller” i
s ta ted tha t ca lc i f ica t ion in asbes tos is i s a lmos t a lways b i la te ra l . Our f ind-
in g of b i la te ra l ca lci ficat ion in a lmos t ha l f o u r cases i s in l ine wi th these
prev ious ly repor ted s tud ies .
However, analys is of
our
da ta p rov ide s
a
f u r t h e r d i m e n si on t o t h e d i ag -
nost ic importance of pleural ca lc if ica t ion insofar as asbes tos exposure i s
concerned . W hi le b i la te ra l ca lc i ficat ion con t inues i t s s ta tu s of be ing a lmos t
pathognomonic of pneumoconiosis (primari ly asbestos is , but occasional
ins tances consequent upon exposure to o th er du s ts
as
w e l l ) ,
unila tera l ca l-
c if ica t ion of the types seen in o u r s tudy s hou ld s imi la r ly r a i s e the ve ry
s t ro ng susp ic ion of p rev ious asbes tos exposure 20 o r more ye a r s be fo re .
Th i s i s pa r t ic u la rly t ru e whe n p re vious t r a u m a t ic o r in fec t ious d isease
has no t been known, when the ca lc i f ica t ion i s ev iden t ly in the pa r ie ta l
pleura , especia l ly when basal
or
medias t ina l in loca t ion , an d i f a ssoc ia ted
w ith ev idence of pa renchym al an d /o r p leura l f ib rosis . In s tud ies e lsewhere,
we ha ve f re qu e n t ly found
a
“calc if ied f leck” on th e di ap hr ag m to be valuable
i n i n t r o d u c i n g
o r
es ta b l is h in g t h e d iagnos is o f asbes tos is .
It
i s s ome t ime s
not apprec ia ted how inf req ue nt even un i la te ra l p leura l calc if ica t ion i s ,
e spec ia l ly in the absence of obv ious re s idua l s o f t r a uma t ic o r in fec t ious
pleural d isease .
2H 30a
M
Th e impor tance o f t he f ind ing of
72
ins tances of uni-
la te ra l ca lc i f ica t ion , in add i t ion to 73 bi la te ra l ca lc i f ica t ions , among the
392 m e n w i t h m o r e t h a n
20
ye a rs s inc e ons e t
of
exposure
is
e v ide n t a nd
emphas izes th e d iagnos t ic va lue o f th is f inding .
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I t is diff icul t
t o
r e la t e o u r f in d in g s i n t h i s g r o u p of m e n w i t h t h e r e s u l t s
o f o t h e r s t u d i e s i n s o f a r as i nc i dence is c o nc e rn e d . S m i t h f o u n d n o i n -
s t an ces of ca l c i fi ca ti on am o ng 261 a s b e st o s w o r k e r s b u t t h e w o r k e x p e r ie n c e
of t h e m e n s tu d i ed i s n o t g iv e n . If t h e g r o u p s t u d i e d b y h e r h a d h a d s h o r t
w ork expe r i ence , t he f i nd i ngs w ou l t l no t he unexpec t ed . J acob and B oh l i g
f o u n d a n i n c id e n c e o f five p e r c e n t a m o n g t h e i r c as es b u t c o r r e l a ti o n s
w i t h d u r a t i o n o f e x p o s u r e w e r e n o t r e co r d e d . I t
is
p os si ble t h a t t h e d u r a -
t io n o f e x p o s u r e i n m a n y o f t h e i r c as e s w a s s h o r t s i n ce t h e D r e s d e n a s b e s t o s
i n d u s t r y h a d s u ff e re d s e v er e ly d u r i n g t h e a i r r a i d s of t h e
last
w a r a n d m u c h
of i t s w o r k f o r c e w a s d i s p e r s e d . T h u s , of t h e a s b e s t o s w o r k e r s u n d e r ob-
s e r v a t io n b y J a c o b a n d B o h l i g i n 1955, v e r y f e w w e r e o b s e r v e d w h o s e
e x p o s u r e h a d b e g u n m o r e t h a n
15
ye ar s before .. , I n Kiv i luo to ' s se r i e s of
env i ronm en t a l ca ses onse t
of
exposu re cou ld no t , of cou r se , he de t e rm i ne d
nor cou ld t h e i n i ti a l cohor t o f t ho se exposed be know n , t o a ll ow a n e s t i m a t e
of
i nc id e nc e o f c a lc if ic a ti on a m o n g t h o s e e x p o s e d . I n t h e s t u d y o f F r o s t
r t
u / . ,
a l th o u g h a n a t t e m p t W:IS m a d e t o X - r a y e a c h of t h e 34 m e n w h o h a d
been a t w o r k f o r 20 y e a r s o r m o r e , n o d e t a i l e d i n f o r m a t i o n i s g i v e n c o n -
c e r n i n g t h e o r i g in a l c o h o r t w i t h w h i c h t h e s e m e n w e r e a s so c i at e d , e x c e p t
t o n o t e t h a t t h e C o p en h a g e n U n io n h a d h a d a b o u t 100 m e m b er s d u r i n g t h e
1930 s;
31 w e r e a v a i la b l e f o r t h e s u r v e y r e p o rt e d .
C o m p a r i s o n w i t h r e p o r t e d f i nd i n g s o f c a l ci fi ca ti on a m o n g a s b e s t o s i n -
s u l a t io n w o r k e r s a r e p a r t i c u la r l y d i ff i cu l t b e c a u se o f t h e p a u c i t y d f s u c h
r e p o r t s . F l e i s c h e r a n d c o ll ea g u es ' ' c o n d u ct e d a n X - r a y s u r v e y of
a
l a r g e
g r o u p of a s b e s t o s i n s u l a ti o n w o r k e r s a n d m a d e n o m e n t io n o f f i n d i n g a n y
ca l c i f i ca t i on am ong t hem .
H o w e v e r ,
9 4 8
of t he 1 ,074 m e n X - r a y e d h a d
w o r k e d f o r l es s t h a n f iv e y e a r s a n d o n ly 51 m e n h a d w o r ke d f o r m o r e t h a n
10 yea r s . Pa ren t he t i ca l l y , i t m ay w el l ha ve been t h e f i nd i ngs conseq uen t
u p o n s u c h r e la t iv e l y s h o r t p e r i o d s o f e x p o s u r e t h a t le d t h e m t o c o nc lu d e
t h a t a sbes t o s p i pe cove r i ng of nava l ves se ls is
a
r e l a ti ve l y s a f e ope ra t i on .
Th e d if fi cu lt ie s a s soc i a ted w i t h t h e s t u dy o f F ro s t an d co l leagues ha ve
a l r eady been m en t i oned . S i m i l a r po t en t i a l s e l ec t ive e f f ec t is p r e s e n t i n t h e
r e p o r t o f B j u r e , S o d e r h o lm a n d W i d i m s k y, s in c e t h e m e n e x a m i n e d w e r e
all
v o l u nt e er s a n d n o d a t a is g i v en c o n c e r n in g t h e c o h o r t f r o m w h i c h t h e y
w e r e se le cte d.' F o u r of t h e e i g h t m e n e x a m i n e d were f o u n d t o h a v e p l e u ra l
c a lc if ic a ti on . I n t h e h i s t o r y o f w o r k e x p o s u r e , n o i n f o r m a t i o n
is
g i v e n
c o n c e rn i n g t h e r e l at io n o f t o t a l e x p o s u r e t o l a ps e d t i m e f r o m o n s e t of
e x p o s u r e .
A m o n g o u r c a s e s, w e f o u n d v e r y f e w w h o se c a lc if ic ati on a p p e a r e d i n
l e s s t h a n LO y e a r s f r o m o n s e t o f e x p o s u re . T h e r e w e r e f o u r ca s e s f o u n d
w h o s e w o r k e x p o s u r e h a d b e g u n l e s s t h a n
20
y e a r s p r i o r t o t h e d a t e o f
exam i na t i on an d on ly one of 555 m e n e x a m i n e d w h o s e e x p o s u r e b e g a n l e s s
t h a n 16 y e a r s 12 y e a r s ) b e fo r e e x am i na ti on . T h i s
is
n o t to
say
t h a t c al -
c i f i c a t i o n c a n n o t a p p e a r i n p e r i o d s s h o r t e r t h a n 10 y e a r s . E l s e w h e r e , w e
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364
Annals
New
York Academy
of
Sciences
have seen a smal l a re a of ca lc i ficat ion on th e per ica rd ia l p leura in a n o il
bu rne r r e pa i r worke r , e xpos ed to f r e q ue n t u s e of a s be s to s c e me n ts , e xa m-
i ne d s ev en y e a r s a f t e r b e g in n in g w o r k i n t h i s t r a d e . E n t i c k n a p a n d
Smither ' repor ted
a
man who d ied
at
t h e a g e of
78
whose exposure began
in
1942
a nd whos e c he s t X- ra ys f rom
1948
onwa rds s howe d e x te ns ive
p leural ca lc if ica t ion b i la te ra l ly . A s no ted , no ment ion i s made in th e pa per
b y B j u r e
et d.'
f d is t inc t ion be tween lapsed t im e f rom on se t of exp osure
and to ta l exposure ,
so
t h a t i t i s d if fic ult to e va lua te th e a ppe a ra nc e of
p leura l ca lc if ica t ion in one man in the i r g ro up who is repor ted t o have had
seven years o f exposure .
Th e obs e rva t ions a mo ng th e g roup of m e n s tud ie d by us
i n d ic a te s t h a t
at
least
am on g workmen exposed t o asbes tos in th e course o f insu la t ion
work , unde r th e c ond it ions wh ic h ha ve ob ta ined in the U n i te d S t a te s a m ong
un ion in s u la t ion worke rs in the pa s t
50
years, pleural calcification
is
ve ry
uncommon i n l e s s th a n 20 ye a rs f ro m ons e t o f e xpos u re .
Summary
1.
Roentgenographic s tudy of
1,117
asbes tos insu la t ion workers showed
pleural calcification to be a common finding. Altogether,
150
instances of
such calc if ica t ion were present .
2 .
Da ta i s p re s e n te d wh ic h de m ons t r a te s th a t p le u ral c a lc if ic at ion a m ong
workme n e xpos e d to a s be s to s in th i s t r a de ra re ly oc c u rs in l e s s tha n
20
years f rom onse t o f exposure . P leura l ca lc i f ica t ion was found in
5 of 725
a s be s to s in s u lat ion w orke r s w i th l e ss tha n
20
ye a rs f ro m ons e t of e xpos u re
b u t i n
145
of
392
me n e xa mine d m ore tha n 20 y e a r s f r o m b e g i n n i n g w or k
with asbes tos . S imi la r ly , the ex ten t o f ca lc i f ica t ion a lso inc reased wi th
dura t ion of exposure .
3. Ava i la b le da ta s ugg e s t s th a t bo th to ta l a m oun t of e xpos u re as well
a s l a p se d t im e f ro m ons e t of e xpos u re
are
of impor ta nc e . In th i s g roup
of
me n , th e e a r l i e s t c as e se e n wa s in a ma n e xa mine d
12
y e a r s f r o m o n se t
of exposure. E lsewhere , somew hat sho r te r pe r iods f r om onse t of exposure
have been no ted , bu t such cases a r e ra r e .
4. App roximately half th e case:; were bi la tera l . I n unila tera l cases , in-
vo lvement of t he le f t hemithorax predom ina ted . Ex tens ive ca lci f ica tion was
usually bi la tera l .
5. Bila tera l p leural ca lc if ica t ion is a lmost pathognomonic of pleural
disease associa ted with pneumoconiosis . Asbestos
is
by f a r t h e m o s t co m-
mon ind us t r ia l du s t invo lved an d b i la te ra l p leura l ca lc if ica t ion in th e
absence of ev idence of t ra um at i c o r in fec t ious p leura l d isease can usua l ly
be cons idered to be due to asbes tos exposure .
6.
In ha l f the cases , the ca lc i f ica t ion found was un i la te ra l . The appear-
ance and loca t ion of such calcification
is
descr ibed and no por t ion of the
p leura w as found to be immune . Th e d iagnos t ic im por tance of such un i -
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Selikoff Pleural
Calcification
365
l a t e r a l c a l ci fi c at io n i s s t r e s s e d s i n c e e v e n u n i l a t e r a l c a l ci fi c at io n i s u n -
c o m m o n i n the g e n e r a l p o p u la t io n a n d w h e n i t o c c u rs ,
a
t r a u m a t i c o r
i n f e c ti o u s h i s t o r y c a n g e n e r a l ly b e o b t a i n e d . W h e n t h e c al ci fi ca ti on i s
i d io p a th i c , i t s h o u l d s t r o n g l y s u g g e s t a s b e s t o si s a n d
the
p r e s e n c e o f u n i -
l a t e r a l p l e u r a l c a l c i f i c a t i o n i s a l m o s t
as
s t r o n g l y d i a g n o s t i c of a s b e s t o s i s
as
i s b i l a t e r a l c a l c i fi ca t ion .
7.
T h e p l e u r a l c a lc i fi c at io n
is
p r i m a r i l y f o u n d i n
the
p a r i e t a l p l e u r a ,
m o r e h ea v i ly i n t h e lo w e r p o r t i o n s of t h e c h e s t . Data c o n c e r n i n g c o r re l a -
t i o n s w i t h p l e u r a l f ib r o si s a n d a s b e s to t i c p a r e n c h y m a l fi b ro s is i s g i v e n .
P l e u r a l c a lc if ic a ti on n o t i n f r e q u e n t l y i s p r e s e n t i n t h e a b s e n c e o f v i si b le
p l e u r a l f i b ro s i s a n d o c c a s io n a ll y m a y b e p r e s e n t i n t h e a b s e n c e o f r a d i o l o g -
i c al ly v i s i b le p a r e n c h y m a l f i b r o si s .
8.
In a d d it io n t o s t a n d a r d p o s t e r o a n t e r i o r f il m s, i t h a s b ee n f o u n d a d -
v a n t a g e o u s t o
use
t w o a d d i t io n a l s i m p l e te c h n i q u e s
; a
s econd pos t e r o -
a n t e r i o r f i l m t a k e n w i t h
a
s l i g h t l y more p e n e t r a t i n g t ec h ni qu e a n d t h e
use
of ob l ique pro je c t ion s .
9. A t t h e p r e s e n t t i m e , i t i s l ik ely t h a t a s b e s to s e x p o su r e i s the m o s t
comm on ca us e o f p l eu r a l c a l c i f ica t i on . T h e f i nd i n g o f s u ch ca l c i fi ca t ion as
d e s c ri b e d h e r e g e n e r a l ly i n d i c a t e s a s b e s t o s e x p o s u r e m o r e t h a n 20 y e a r s
be f o r e .
Referen ces
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
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