Selikoff - Asbestos Insulation 1965

8/20/2019 Selikoff - Asbestos Insulation 1965

1/17

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


2/17

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


3/17

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 .


4/17

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 )


5/17

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


6/17

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


7/17

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


8/17

358

Annals New

York

Academy of Sciences

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


9/17

Selikoff

:

Pleural Calcification

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


10/17

360

Anna ls New

York

Academy of Sciences

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-


11/17

Selikoff Pleural Calcificatioii

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


12/17

362

Annals New York Academy of Sciences

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 .


13/17

Seiikoff

Pleural

Calcification

363

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


14/17

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 -


15/17

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.

12.

13.

14.

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A . C.

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COOKE,W .

E. 1924.

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K.,

T .

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P.

PENDEKGRASS.

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A m .

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J.

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366

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York

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of

Sciences

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

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37.

38.

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40.

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WOOD,W .

B.

S R. GLOY NE. 930. Pulm ona ry asbestosis . Lancet 1 : 445-

448.

ELLMAN,

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WOOD,W. B.

S.

R . GLOYNE.1934. Pulmonary asbestosis. A review of one

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FULTON,. B., A. DOOLEY, .

L.

MA TTIIEWS R. L. HO UTZ . 935. Asbes-

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fab r i ca t ing p l an t s on the hea l th of a g ro up of workers . D epa r tm en t of

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50:

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B.

1936. A survey of a g r o u p of employees exposed to as-

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J .

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229-239.

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M. D IIR K A N . 955. The effec ts

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15:

69-81;

15:

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15:

152-159.

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Documents

Selikoff - Asbestos Insulation 1965