Document b5Qxa37VkbBb3N6VELpnZ7wpg
FILE NAME Manhattan RBM
DATE 1977 June 22
DOC RBM053
DOCUMENT DESCRIPTION Unpublished Presentation - Medical Aspects of Occupational Exposure to Asbestos
[7
MEDICAL
MEDICAL MEDICAL
ASPECTS
ASPECATSSPECTS
ASPECTS
ASPECTS
OF OF
OCUPATIONAL OCCUPATIONAL OCCUPATIONAL
OCCUPATIONAL
OCCUPATIONAL
OCCUPATIONAL
Lewinsohn MB
Medical Director
.
Raybestos
Manhattan Inc.
100 Oakview Oakview Drive
Trumbull Connecticut 06611
Talk to Members of Friction Annual Meeting
"
.It always pays to define asbestos even when it seems that it is unnecessary to do so because of the sophistication
of the audience being addressed Asbestos is a generic
tem for a variety of hydrated silicate minerals which have one common attribute namely the ability to be separated
into relatively soft silky fibers Although the name is ordinarily associated with those varieties which have technologic importance it is applicable to all minerals which fit the above description The term asbestiform
minerals is perhaps most descriptive
There
There
are
are
two two
main
main main
classes classes
classes
depending
depending
depending
upon
upon
tthheeiir r
their
their
crystal
crycstralyscrtyasltal
structure namely serpentine and amphiboles The sole member
of the serpentine class is chrysotile asbestos which comprises
nearly % of world production There are five asbestiform
varieties of amphibole namely crocidolite amosite
anthophyllite tremolite and actinolite
The uses asbestos are many and the chemical
properties of the different varieties determine their commercial
importance The medical complications resulting from exposure
to asbestos are also related to the physical and chemical
properties of this fibrous mineral species
Tin Tin " "
"
a
T PT ETTITTeT fie
PME WAP PH
1
gee
ee At
Se ra IPL
a
B. The Asbestos Diseases and Other Conditions Associated with Asbestos Exposure
1 Benign disabling conditions
a
Asbestos corns warts or callosities callosi warts t or cai llosie ties calls osities callosities
Workers handling raw asbestos fiber as it arrives
from the mines often get splinters in their hands
These splinters may cause an inflammatory reaction
_
which eventually subsides leaving a hard thickened
raised area of skin with a central core of
tissue There is no information available to . in-
dicate whether this mode of asbestos penetration
complication of asbestos warts The skin continually continually
renews itself and the corns eventually merely mark
the spot where fibers once were
b Asbestos Bodies
In Belfast about one in five of elelderly derly men coming
to autopsy had a sufficient number of asbestos bodies
in his lungs for these to be detected by examining
one or two microscopic sections
2
2
Thomson
in
in
1964
1964
reported
reported
on
investigations
investigations
investigations
investigations
which began in Cape Town South Africa in 1960
These investigations were intended to determine the
extent to which the ordinary urban dweller is exposed
by
occupation
or
environment
to
the inhalation
of
of
asbestos Over 25 of the lungs of 500 consecutive
!!!! a
a
{see
1 a Re
3
autopies on subjects of 15 years and over showed
asbestos bodies by the method use~ Thomson started a similar study in Miami Florida in 1961 while
exchange professor there The overall positive
findings were remarkably similar to those in Cape
Town In 25 of the positive cases the bodies were
scanty were not associated with pulmonary changes
and were regarded as the result of
contamination of
the urban atmosphere
e..
In % of all the males examined
the bodies were numerous and were
presumably of
occupational origin
I have classified asbestos bodies under benign
disabling conditions because they are not in
.
themselves indicative of disease Asbestos encapsulated fibers probably inert and indicative
are
of
asbestos exposure The implications of Thomsor.'s
findings will be discussed in this -
paper 3
According to Selikoff asbestos bodies do not appear
randomly distributed among the general population of
New York but are related
to an important extent
occupationally
Asbestos fibers are not all coated and converted into bodies Uncoated fibers may persist for many
years after exposure to asbestos ceases
It would appear that asbestos bodies contain
inactivated fibers and that the uncoated fibers are the t
ones associated with disease causation Other mineral
OEE ee
Sibers can form similar bodies and some people prefer
5 the
the term ferruginous bodies
fiber
Glass fiber
silicon
silicon
carbide filamentous aluminum silicate and fibrous tale
could be confused with coated asbestos fibers 6
Pooley has found that asbestos bodies in mesothelicm
cases from 4 different countries were associated with
amphibole exposure and that asbestos bodies detected in these lungs were all derived from amphibole fibers
c
The lungs are invested by a thin layer of connective
itself in the midline to cover the inner surface of the
chest wall
layers
^ potential space exists between
of Inhalation
.
asbestos dust results in very - CE
characteristic changes in the pleura which can be
regarded as an index to exposure Pleural changes may
also occur after infections such as pneumonia and pleurisy tuberculosis injury to the chest wall and
exposure to commercial talcs
Pleural plaques are defined areas of pleural
thickening which are found on the domes of the diaphragm
along the rib margins and in the gutter which runs along
paravertebral
the margin of the vertebral column - the paravertebral
gutter These may be recognized on rays but often
are not seen and are primarily discovered at autopsy
Pleural plaques or pleural thickening may become
calcified Pleural calcification has been described by
7 Kiviluoto in Finland
These studies drew attention to
the widespread presence of calcification of the pleura
i in n communities exposed to asbestos dust
Kiviluoto
reported on the finding of pleural calcificationcalcification among people in a rural community living in the vicinity of
two open cast
and Michailova recently
pleural calcification and found that pleural calcification among Quebec miners was not due to exposure
to chrysotile itself but to dusts produced during
m min iinnging operations The distribution of cases within the Quebec industry showed that exposure to dusts
responsible for pleural calcification occurred mainly
in
in
Thetford
Mines
and were
therefore
associated
with
local geological formations
Talc and mica in the
Thetford area were considered the most likely agents
responsible for pleural calcification calcification in Quebec
chrysotile workers
Are these pleural changes truly benign or should
+
v
we
fee
a
they be considered as precursors of malignant changes This question cannot yet be answered adequately but in Gibbs study persons with definite and suspected pleural calcification showed no overall excess mortality when compared with all persons employed in the Quebec
asbestos mining and milling industry industry born between 1891
and 1920. Elmes found pleural plaques in 25 of cases
of mesothelioma studied by him in Belfast He stated
thatthatthat that
when
when when when when
the the the
exposure exposure exposure exposure exposure exposure
was was was
mixemdixed mixed mixed mixed ,
i.e. i.e. i.e. i.e. to more than one
population seemed to indicate a level of exposure
capable of producing mesotheliomas mesotheliomas Edge
shipyard
shipyard
shipyard shipyard shipyard
shipyard shipyard
workers
workers
workers
with
with with
pleural pleural
pleural
pleural plaques who
had
mixed
exposure to asbestos without evidence of pulmonary
lung
cancer when compared
Leathart12 described
increased
witinhcreased
the lung
general population
function results in
191 asbestos workers and concluded that asbestosis was
usually but not always associated with lung function
defects
on lung
while pleural calcification alone had no
function Becklake showed that while
effect
pleural
calcification alone appeared to have no adverse effect
on lung function diffuse pleural thickening was
accompanied by a reduction in certain parameters of
pulmonary function
Pleural changes have been known to be associated
with asbestosis for a long time but changing circumstance
ETT ETE tol ETE A TtMr I ieee m mAIh TT Iii Mi en Ihmill vg {IIih oui Di Saal
in industry have and intermittent
reduced dust concentrations in factories
exposure elsewhere The typical
asbestosis is becoming less common and less
severe than
it used to be and has become
replaced by a very slowly
. '
progressive disease in the lungs while the well re-
cognized pleural changes are still occuring to the same
extent because
These pleural
the underlying
changes have lung disease
become more is minimal
obvious There
may well be some instances where pleural changes
in the absence of underlying lung disease
occur
20 Asbestos Diseases
a
Asbestosis
Asbestosis is a fibrosis or scarring of the lungs
resulting from
fibers
fibers
high
in high
the inhalation
concentrations
concentrations
of respirable respirable asbestos
usually
usually
a
for
a
prolonged
prolonged
period of time
Some authors include include include include include the the the associated associated associated associated associated asociated associated as ociated associated as ociated
thickening of the visceral pleura in this definition
The dependent lower parts of the lung are
affected af ected affected affected affected affected affected affected first first first first first and and the process progresses as the years
| go by even after exposure ceases The diagnosis of
asbestosis depends on
1 history of exposure
2
finding of fine inspiratory crackles crackles at the lung bases on
auscultation with a
stethoscope
3 clubbing of the fingers
diagnostic sign
not an essential
4 ray changes
5 lung function changes indicative of restriction of ventilation or impairment of gas exchange
The ILO / International Classification of
Radiographs of Pneumoconiosis 1971 has been developed for epidemiologic purposes and is descriptive not
diagnostic A diagnosis of asbestosis can only be made
by examining the worker the ray the lung function
tests and the occupational history history Other respiratory respiratory
diseases such as chronic bronchitis emphysema asthma Y
and
and
certain
certain
chronic chronic
chronic
lung
lung
diseases
diseases
can
be
be
mistaken
mistaken
for
for
The severity and
progression of asbestosis appears
to depend on the amount of
From the time symptoms are
asbestos retained in the first noted most workers
lung
can
-
- - continue to work for 10 to 15 years and may live another
5 to 10 years after finishing work usually having had
to reduce the work in
gradual stages because of
increasing shortness of breath Asbestosis is unusual
under the age of 50. Other conditions leading to the
necessity for light work and early retirement may precede
asbestosis in this age group As mentioned earlier
improving industrial conditions conditions over the past 20 years
have resulted in a less severe form of asbestosis than v was seen in the 1930's 1940's and 1950's This disease
process may not appreciably shorten life in
present
day circumstances
b Asbestos Cancer
According
to
14
Gilson
it
was about fifty years
after the
commercial exploitation of
asbestos began
that lung cancer was first thought to be caused by
the dust 1935 about
another ten years before this
v
was
generally
thought probable
probable
1945
and further
ten before it was finally established in the asbestos
resulting from exposure to
conditions
previously previously 40 years years
previously
previously
In some sections
industry
industry
industry
industry
industry
the
the
effect
effect
effect
of of
of
improvements
improvements
improvements improivmperomveemenntts s
in
in in
more than 30
of the
asbestos
dust
dust dust
dust
control control control
>
on
on
the reduction of asbestosis
incidence
ing contrast
according to Gilson
risk in
between
chrysotile miners and milmilllers ers in 1891 and 1920 and the high risk
Quebec in the
born
in-
sulation workers where exposures have been to
mixture of chrysotile and amosite in the U.S.A. or
U.K. ) to these two and crocidolite in the Asbestos fibers have a large surface area and
readily allow adsorption of other materials materials
Lung
cancers have been blamed on substances adsorbed
on
to the fiber such as trace metals
cigarette smoke
and hydrocarbons
is important and
from other sources Cigarette smoke
the interaction of
cigarettes and
|| IE TEE
TETSa R
MT
||
;
MT TA : '
SII
SEEyM ume a
CH
ey et e
pg spe gg iil al
=
10
asbestos exposure has been well documented by Selikoff
smoking asbestos workers rarely get lung cancer The types of lung cancer in smoking asbestos workers
do not differ in their effects from primary lung cancers in other people The majority of affected individuals
die within a year of diagnosis Although lung cancer is usually associated with underlying underlying asbestosis some
authorities authoaurthoriitiestiautheoritsies believe that this is not always the case The risk of premature death from malignant chest disease
seems
to be
confined
to
those with high
dust
dust
exposexpuosurerexposure e
Asbestosis Asbestosis
Asbestosis
Asbestosis
usually usually
usually
usually usually
no
longer
kills
kills
killskills
because because
because
improved
improved
dust conditions have resulted in
milder form of
disease Less mortality from asbestosis occuring ocuroing ccuring occuring occuring after
longer periods of exposure has resulted in survival of
workers through the long latent period of lung cancer
c Mesothelioma
The association between exposure to asbestos and
diffuse malignant mesothelioma first attracted wide
uu
attention through the publication of a series of South
African cases by Wagner Sle^^sand Marchand 1950
Subsequent comparisons between cases of this patho-
logically controversial condition and control patients
have confirmed a statistically significant association
with hood
asbestos Wagner et al also showed that neighbor-
or community exposure could be associated with
this malignant tumor
1
aa
EET ELTETT T e
ggpe
11
Exposure in some cases may be of brief duration
and there is a long lapsed period latent interval between first exposure and diagnosis or death This lapsed period may be from 20 to 40 years or more Disease diagnosed today probably had its causation causation causation in in working conditions which prevailed between 20-40 years
The tumor affects the pleura grows slowly doesn't
spread readilyreadily to other parts of the body and it kills
by slowly compressing the lung and vital structures structures
associated with it
Peritoneal tumor is less common
and is
similar in its
effects The tumor can occur
from about the age of 35 onwards but more than 50 do
not develop until after age 60
not seem to be a causative
Cigarette smoking does
Cigarette -
According According
to
a
review
of
the
epidemiology
epidemiology
epidemiology
of
mesothelioma from estimates of incidence presented by
Alison and Corbett Corbett McDonald at the XVIII International
Congress on Occupational Health in Brighton in 1975 the incidence of mesothelial tumors is
extremely high in three situations among insulators among those who work in or live in cities with shipyards and among those who work in or live in certain cities with large asbestos
plants
The most definite association with mesothelioma
is following exposure to crocidolite fibers from the
Cape Province and Transvaal in South Africa and from
a a a 0
12
Western Austraiia, McDonald McDonald McDonald
concluded Western there ere
indications most types
of exposure exposure that @ gradient in the
mesothelioma inducing potential of gradientifniber with
crocidolite the most most
amosite hezardous,
less hazardous chrysotile chrysotile
least hazardous McDonald has
recently demonstrated that
ceses from the
chrysotile mines Quebec Quebec Canada&, Were
due to crocidolite Crocidolite used for the the
Canadian army respirators and this fiber processed
S&C the site of the
major Canadian chrysotile
processed mine
experience used Crocidolite was
similarly
The Canadian ^as
mask workers
in gas masks Britain
ezecc
Eriteis,
on the same
= process using Australian Australian Crocidolite ir.
Nottingham England
of mesothelioma after
McDonald c^'lculetes tha- the crocidolite
expcsure in least
risk
circumstances described
would ePppear to be chrysotile chrysotile 50
times greater than that
associateg with chrysotile
production
There There is evidence that the from fibers fibers
et at risk
developing ambient Occupational Occupational histories
measurable measurable in embient air.
which attempted
re deficient in those
Studies measurements with
mesothelioma mesothelioma
correlate
environmental correlations increasing increasing
incidence The correlations between
increasing
G ' E MeN PT eT |
re
13
utilization of asbestos during and since World War II are more reliable indicating the likelihood of occupational risk rather than public health risk
C. The Issues at Stake
There appear to be three major issues at stake at the present
1 Can asbestos products be manufactured se cly
i is there any risk to users of asbestoscontaining products and
ii do low levels of exposure constitute a
.
public health risk
2 Can substitutes be found for asbestos 3 Who is going to provide the answers and make the
-
decisions
:
@eeeeeaceveevoeoeeeveevseeeeveesoseeoeonseveanene ef 8
1 Manufacturing of Asbestos Products
myriad
The uses of asbestos are myriad
Many
_
of the
E,,,
uses
of asbestos are probably unnecessary and continue because
o
ee
ee ee
traditions die hard It cannot be replaced by suitable
Vv .
i
:
substitutes as yet in many areas
There is satisfactory evidence in the world literature
to indicate that asbestosis is a response related
disease There is furthermore adequate evidence that a
reponse also exists for the carcinogenic properties of
asbestos The fibrogenic ability to produce lung fibrosis
14
effect and the carcinogenic cancer producing effect of
be asbestos appear to
similar for all varieties in commercial
use The scientific opinion with regard to the proposed
gradation of effect attributed to crocidolite amosite
,
chrysotile tremolite and anthophyllite in the production
of diffuse malignant mesothelioma of the pleura or peritoneum
is divided Although most observers believe that crocidolite
particularly that from Australia and the N.W. Cape Province
of South Africa is the most dangerous fiber that amosite
holds an intermediary position and that chrysotile presents
the least hazard some authorities do not accept this thesis
Having weighed the evidence presented by both schools of
thought I am of the opinion that crocidolite has greater
mesothelioma producing potential than amosite or chryschile and that its use should be strictly curtailed In the
United Kingdom the use of crocidolite has virtually
disappeared and no raw fiber has been imported or handled
in production since 1970
In reviewing the literature it is obvious that advances
in the control of asbestos manufacture did not proceed at
7
the same
Industry
pace in the
Regulations
industrialized world / The Asbestos
1931 which came into effect in the
United Kingdom in 1933 preceded the rest of the world by
approximately 40 years or if not impossible to make
more . Although it is
comparisons of working
difficult
conditions
in different countries for the same type of industry there
are indications that the health experiences are different
a
ial a TP AE a
SST CN
DS Sl
not
totally totally
not suitable for
L
analysis
{
Environmental Hospital Hospital in
Sciences
Chrysotile asbestos
New
miners miners
in in
equally
Quebec Quebec have
studied
Nicholson Nicholson
demonstrates quite
McDonald
Nicholson
clearly the a
20
which
which
16
Asbestos Standards which was published in 1968 and recommended a cumulative standard of 100 fiber years for chrysotile
asbestos In 1970 NIOSH reported that records of dust
concentrations between 1930 and 1967 in one asbestos textile
factory and between 1948 and 1969 in another were assembled
in
i in n in the Pennsylvania Department of Health In report _
presented at the Western Industrial Health Conference by
Howard Ayer it was disclosed that using using lung function as
the most sensitive indicator of asbestos health effect it
appears that cumulative exposures below 50 fiber years cause
no reduction in FVC and exposures greater than 200 fiber cc
years
are
usually usually usually usually
usually
associated
as as ociated sociated associated
associated
with
with
reduction reduction reduction
in in
FVC
FVC
If If
If
this
this
exposure
exposure
were
were
spread
spread
over
30 30
years
years
this
this
would
would
would
mean
mean
no reduction in
7 fibers would usually lead to a reduction in FVC as well as ray changes in 10 or more of workers
le
we
come
me.
OHS
ee
ayes
TR
The present standard in the U.S.A. and most of the
world is 2 fibers and is based on the BOHS Standard for
chrysotile
In the United Kingdom and and certain certain certaincertain other countries
crocidolite is dealt with more stringently because of its
association with mesothelioma
In October 1975 OSHA proposed
of
a tightening tightening tighteningtighteningtightening tightening tightening tightening tightening tightening of of the standard to 0.5 Fibers and in December
1976 NIOSH recommended that it be 0.1 fiber
The argument regarding the adequacy of the standard is
dependent upon the no safe threshold for a carcinogen theory
There is qualitative evidence that the 1931 Asbestos Industry
.
a
eee RE Se Oe
17
Regulations in the U.K. had the effect of markedly reducing the incidence of asbestosis and similarly reducing the excess
deaths from lung cancer in the same factory studied by the
23 BOHS
Some residual effect is still being seen in this
factory because dust levels were still relatively high in
many areas until very recently Bearing in mind that the
BOHS Standard was not published until 1968 that new Asbestos
Regulations were not made in the United Kingdom until 1969
and that the 2 fibers standard was not officially applied
there
there "
there
until
until
1970
1970
1970
it
it
is
is
obvious
obvious
obvious
that
that
no
conclusions
conclusions
can
as
yet be drawn with regard to the level of risk still attached
to working in conditions in total compliance with this standard
asbestos manufacture the answer to the question posed is
obviously that we do not know for sure but
the evidence
is pointing towards the conclusion that when adequately
controlled the risk of asbestosis and lung cancer can be
reduced
reduced
reduced
to
virtually
virtually
virtually
nil
nil
Dr.
Reach
24
Reach
has
summed
summed
up
the
situation as follows
A problem arises when it is appreciated that there is
no exposure which can be said to be
risk There is no single threshold
absolutely free
of of
of
exposure held in
common by everyone There is consequently this gradually increasing risk in relation to exposure The application of dust control to meet a TLV an MAC MAK value or other similar hygiene standard will limit and
control the risk but is unlikely to reduce it to zero
It has to be remembered that asbestos is very widely
used and brings real benefits to the community A standard could be made so stringent that the
at large
cost of
dust control is prohibitive that the production and
use of asbestos ceases to be economic production
use is discontinued and
the
associated
associated
benefits
are
lost The benefits gained by reducing reducing the risk of
y
SS MITTEE TT] li rnp) rT Fe TPT pn ef [i WIN
fh ale pital reife 7 Myre j i ae Oa
asbestosis through reducing air contaminant exposure have to be weighed against the possible loss of direct
and indirect benefits to the community from the use of
the material
He goes on later to remark
The air quality attained in industry in different
countries does differ and no doubt will continue to differ A wealthy country can afford to spend more
_
money on aircontaminant control Also a country very conscious of the slightest risks to which its
workers may be exposed through their
expected to have different standards
not
where
other
health
health
health
health
health health
risks risks
may
be
occupation may be
from one which is so much the greater
benefits
the the the
products products
balance balance balance balance balance balance balance against against
that that would
exposure
the community from the use of inexpensive products have in some measure to be weighed in
against the benefits to the health of the
accrue by reducing asbestos dust
The further comments of Dr. Roach are of interest and I quote
To derive hygiene standards for an air contaminant which
provide a known degree of protection against a health
hazard it is necessary to have a body of data showing
the amount of air contaminant to which people are exposed
and the corresponding effects or lack of them in the people
It is also necessary have grasp of the consequences
-
to industry and users of limiting and controlling emissions
of the contaminant Our present information is very
imprecise particularly in terms of the practical
consequences of recommendations
Hygiene Society
specific hygiene
for a hygiene standard
committee found
relationship between exposure and
area of uncertainty A much more
problem was to decide on what in
level of dust control
standards In developing standard the British Occupational
that knowledge of the the
risk risk was not the greatest difficult difficult and contentious
fact fact was an acceptable
More information is needed for example on the expense
of
dust controcontroll .
Where this is done by ventilation it is
important
know
know
know
what
what
is
the
the the minimum amount and what kind
exhaust
ventilation
ventilation
exhaust ventilation and
dilutidon ilution ventilation is
Recessary to achieve achieve a given degree degree of air cleanliness in a
work place
since
costs
tend
to
to climb as
the
cube of the
Research is needed to determine the balance balance between local and general ventilation which produces a specified degree of control at minimum cost By setting setting down the capital
19
o
cost installation cost running and maintenance costs
it becomes possible to grasp more firmly the consequences
adopting of
particular hygiene standards This kind of
information is needed throughout the field of asbestos
dust control so as to be able to weigh up the costs of
achieving high air cleanliness
This does not reduce the choice of an air quality standard
to a mathematical equation nor does it avoid the need
to exercise wise judgment in the choice of standard
_
the However
judgment can become a little less
arbitrary than at present
The second question posed under the above heading is in
regard to the risk to users of asbestos containing products
Asbestos is used throughout industry and until recently
outside of the manufacturing industry users took few 2
any precautions Because asbestosis is related no
immediate
immediate
immediate
health health
hazard
hazard
was
was
apparent
apparent
apparent
from
from
this
this
cause
cause
in
in
users
users
cf
cf
asbestos
products
products
products
The
exception
exception
exception
to tt hishis
rule
rule
is
is
in
in
the
the
insulation industry where the upsurge of cases became marked
SS
nie
a.
in the late 1950's and early 1950's probably as a result of
the increase in asbestos usage under poor conditions during
ne
World War II The process of spraying asbestos onto girders
enn
of rise buildings
spraying asbestos on the interior ci
nn
buildings for heat and sound insulation and the extensive use
of this process in navalbuilding
one
of
.
the
most
hazardous
uses
ever
operations Mechanical operatoperaitoipoenrsoationsns
such as the sawing
drilling or abrading of asbestos products
ee
will
create
_
tools The
dust and
quantity
power tools create
more dust than
.
of dust produced will also depend
hand on the
amount of asbestos in the product and the nature of other
components Most demolition processes where asbestos
Any lucts
)
fn.
vel
ies +
P~ ro~ducts are beiss re;
removed products are being
.
asbestos asbestos
result are
usually exposed
asbestos products
intermittently products dose dust dust the same period
and
accumulate accumulate
period time
continuously exposed
time
workers
manufacture manufacture asbestos
asbestos
Mesothelioma may occur the absence
products kes
occurred
absence asbestosis
electricians
in plumbers
carpenters Mesothelioma Mesothelioma were
workers exposed in the
etc. etc.
vicinity insulation insulation
using asbestos It has
Workers
PeETSOAS Who
also been = <porced
have lived in
mines
close
ene milis and
proximity crecidolite crocidolize
factories or
crocidolize
building @sbestos asbestos used From all the
sizes at epidemiological
there
epidemiological ere between 5-30 % mesothelioma
no there
cases of
no
evidence evidence
mesothelioma in It been
exposure exposure
shown shown
asbestos cen Se urban community community
nearly everyone who lives in
has
en lungs
comunity has
There There has been great
Geal os
asbestos
health in terms
brake terms exposure exposure of
surveys conducted
Constitute mechanics
service population
conducted on
The epidemiological epidemiological epidemiological o=
have
carried
population very very recently by available
and no epidemiological epidemiological
There There appears to
evidence
available es in
some
service
of
service mechanics mechanics
radiologic Selikoff Selikoff
the group
evidence
studied studied Selikoff
frank disease disease
Group
American American
Thund of frank
At At Annual American
Cisease,
Travers
month NICSH presented data showing that the use of proper work
practices would reduce the asbestos exposure of brake service
mechanics to an extremely low level Approximately 20th of the presently permissible OSHA level NIOSH will shortly issue ^ technical bulletin outlining acceptable work practices The
recommended work practices will be almost identical to in-
structions provided by Raybestos to all friction
material customers for the past 2-1 years
There is obviously some risk attached to the use of certain
asbestos containing products but many give off no dust and
4
others once incorporated in machinery ,
etc. never again see
the
use
light of of day
Great care
ee
of asbestos and materials
should
.
alwaysalways
be
-
taken
in
the
containing and the dust levels
should always be bulow the minimum required nese
The main non-
industrial
materials
use of asbestos is in yourself building
There are also some domestic products which contain
asbestos such as some electrical appliances There is
negligible risk of fibers being dispersed from domestic products
in normal use provided they are in good condition
_
ST,
To prevent
sho(uld always be
the misuse of asbestos products warning
affixed and work practices advised }
labels
In answer to the third question it should suffice to say
that there is no published epidemiological evidence to support
the hypothesis of a possible danger to the general public
The biological effects of asbestos have always manifested
Pa |
.
themselves in individuals or groups of individuals exposed
to dust concentrations many orders of magnitude greater thar
;
22
levels measurable in the general environment One major area
of concern is the ingestion of fibers from water carried in
asbestos cement pipes or from the filtration of wines beers
spirits beverages etc. through chrysotile asbestos filters
This concem arises mainly because of the demonstration of an
excess incidence of intestinal cancer in certain heavily-heavily-
exposed asbestos insulation workers and heavily exposed textile
workers It is interesting that the textile workers studied by
the BOHS do not exhibit a
similar
excess
mortality
from
from GI
cancer
If the use of chrysctile asbestos filters is discontinued this
would be a retrograde step The ingestion of chrysotile asbestcs
and other types of fibers in experimental animals has failed to
produce mesotheliomas
From human
evidence only people with a
severe exposure to asbestos dust have contracted peritoneal
mesotheliomas and these tumors have not been found in any of
the asbestos mining areas except those mining crocidolite in
spite of the very heavy dust exposure especially in those
exposed to chrysotile
Asbestos Substitutes
The major health problem associated with asbestos exposure
is mesothelioma As has been stated earlier in this paper
asbestosis can be controlled and lung cancer appears amenable to similar controls but because the latent period between first exposure and diagnosis of mesothelioma is long and this malignant tumor's association with asbestos exposure is a recent discovery sufficient time has not yet elapsed to determine the level of dust capable of producing this response Some evidence
a
23
has emerged that mesothelioma is dose related but more time is
needed to determine this dose The gradation of effect previously
discussed important in the context of prevention The
reason Fosr this gradation of effects are of importance and may
determine the feasibility of using other fibrous materials as .
substitutes for asbestos
The
The
theory
theory
developed
developed
developed
25
byTimbrell
can
can
explain
explain
the the
the
gradations
gradations
gradations
biologic
in biologic potential of the various types of asbestos He
suggests that long fibers are preferentially deposited in the
respiratory bronchicles at bifurcations and that this mayexeplxaipnlain
way fibrosis tends to be associated first witwhith respiratory respiratory respiratory respiratory respiratory respiratory respiratory respiratory respiratory
and with long fibers He also suggests that the
characteristic rectilinear shape of amphibole fibers compared
to the curly morphology of chrysotile fibers allows the
amphiboles to penetrate to deeper parts of the lung more efficiently
than chrysotile fibers A reasonable theory has thus been proposed
to explain the reason for the development of mesotheliomas It
is based upon the ability of certain types of fiber to penetrate
deeper into the lung than others and to reach the pleural cavity
by direct penetration
Substitutes for asbestos are being sought although for most
purposes none have been found as yet Other fibrous minerals
are being tried among them glass fibers and mineral wools
Animal experiments indicate that if such fibers were capable
of reaching the pleura i.e. had the same physical physical characteristics
as amphibole asbestos fibers they could produce mesotheliomas
The available evidence depends upon the implantation into the
ee te
24
Pleural C^'vityby spen
Susgical techniques the various
pleural
various
cavity to date, Both Europe
materials
Europe in the United United
tested studies have
States epidemiological epidemiological
failed far to demonstrat demonstrat
to workers the man
carcinogenic carcinogenic is a field very
made mineral :
very active
industry PlOVice
research should should
answers in the nearnear future future
hopefully
future which prevent
hopefully so= SS&
prevent
asbestos tragedy
"AS long es there is
long there any airborne asbestos dust health Never-
environment
may be some small risk health
Never-
&
environment exposure
theless
up
to
certain
limits
tolerated for re
exposure incurring undue
can be tolerated zs>
risks( Acasa 2-
discouraging was
this
picture
With this cefined
of
inadequate inadequate
exposure
ecse of
information enforcement enforcement existing levels
and may
enforcement enforcement what value
before us for
TLYN is for
any welt
carcinogen Should such
asbestos banned from use
2 carcinogen forms Asbestos materialsextensively be used industry industry
insulation for
for
extensively isis extensively
extensively
inclusion in
a
and
United products
for
plastics materials materials
reinforcing stress
.a At At
in thethe
nearly nearly million tons
United
For For
are used
linings is difficult
United States
uses , as brake
difficult find
linings @ replacement
asbestos would
. societal
to ban use of sind
decision not insurmountable insurmountable
insurmountable
create
insurmountable
difficulties
serious would still
control problems
problems
Moreover large quantities quantities
posed by large recourse
of
asbestos
current current . Our asbestos
this time limit
human exposures exposures lowest
and other similarly similarly recognized recognized
carcinogens carcinogens to lowest
possible possible
levels existing
existines technology
possible leveis, with
In In the case that , in
fact Risk Limitation
Recognizing however
Recognizing that defined that risk
implementation implementation of
Limitation
might might can rule
mandate
implementation fraction
available available technology technology which available
Oust out technology fails keep u wp ork processes portion of
technology technology More however
with major portion specification
industry number The however is required work practices and and
number
of a engineering engineering
specification
specification
offers
specification
work
supplement
controls an essential
essential sup lem nt supplement
supplement
numerical . TLV the latter
all
Q Apolics Apolics ApolicsApolics Apolics
numerical TLy s+ the
used Sup
latrer fs used at aly.
ADD ents an
25
of many economically and technically feasible procedures
can reduce exposure to levels much below existing numerical numerical
values These should be mandated Moreover such procedures procedures
can be specified with joint government
cooperation and can be monitored much more readily than
can dust concentrations TL's and practice stancards
should be reviewed frequently with a view to achieving
continued reduction in worker exposures The specification
of a proposed TLV can serve as a stimulus for the development
of new engineering methods or to rule out marginal
~
processes that cannot be controlled As new engineering
developments evolve the lowering of a minimal standard
can be undertaken along with the specification of
additional protective work procedures
To a limited extent this has taken place in the asbestos
industry Nicholson
Threshold and dose response are only two of the components
in decision in environmental control and regulation
In addition to scientific data with all of its present
limitations public health responsibility must incorporate
prudence as a factor in judgment This invokes suon
issues as benefit ratios and risk as recently
reviewed by Falk The benefit ratio at best an
elusive attainment must clearly delineate the cost to
when and benefit to whom The quantitative contribution
to this equation must virtually be entirely cerives froz
data on man The concept of risk - the summation of
threshold and dose response - when applied to population
is indispensably but not exclusively based on human as
well as on experimental data Laboratory contribution to
risk encompasses the entirely tenable
as well as dose response when addressed
concept of threshold
o
to the subject o
the conference the hazards of environmental agents to
san Kotin
Trade Unions
In the past risk assessment has been largely the domain
of academic industrial and government scientists who have
usually waited as long as possible to share their information
workers
.
This discussion will recus on the need for
risk assessment to be a process continually going on at two levels Federal and local
The need for Federal involvement in the standard process is obvious with tasks including carcinogenic risk assessment itself standard enforcement and when necessary further modifications if workers are not being adequately protected The need for worker involvement has only more recently been recognized During this Federal standard process the involvement of workers or their
nn
representatives is critical to the design of an adequate
standard monitoring and medical surveillance Once set
workers must have an active and informed role at the local
level in assuring that the standard is enforced
28
Wolfe
To reiterate the most most
governmentgovernment
will will
will not
be
difficult scientific
decisions to in nature
be made by
Social and
Eoral decisions will be made that can channel and shape the development of our control technology which itself will
become a major determidetermninant ant of our future welfare In this
process labor's contribution is unique -_
Alone among AmericanAmerican publics publics the worker is most exposed
to environmeeennnvviirroonnmmteennttaall al
insuilnsult t
both inin
the the
the
community
and in the
shop while being mo mostst vulnerable to the economic consequences
of control he and his institutions are of necessity
therefore in a position of forced objectivity Thus his
is a critical voice to te heeded
The participation of organized labor is not automatic &
positive effort must be public advocacy This
made
is an
an effort essential
I call positive
government
responsibility responsibility
involving
involving
involving
involving
the
the
public
public
in
processes
such
such as
the assessment of environmental risk
Samuels
( c ) Government and its
Ecencies Ecencies Ecencies
Ecencies
Because the Federal government has provided for a National
Cancer Plan under the leadership of the Director of the
National Cancer Institute it must be this Federal agency that provides overall leadership for an effective integrated
national program for prevention and control of occupational
A cancer splintering of responsibility for research and
training can work only to the cetriment of the worker The
NCI cannot retreat from its responsibility to provide
with regulatory
agencies
with
with
with information information concerning risk of
exposure to specific chemical physical and parasitic
.30.30
agents demonstrated to induce tumors Lassiter
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~
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E. E.
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"
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Ann
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Integrated
Program
of Governmental
of
Occupational
Action
Action
Occupational Ocupational
TEED TEE] VEE
Rageae