THE WESTERN CANADIAN LUMBER WORKER

textiles. I have already men-
tioned that in recent years
there has been an increase in
cases of asbestosis in Britain.
As if that is not enough cause
for concern, the disease is ac-
companied, in about 16 per
cent of cases, by cancer of
the lung.

LUNG CANCER

There are two types of lung

cancer associated with asbes-
tos. One is a similar type to
the cancer related to cigarette
smoking. The other is a dis-
ease of the covering of the
lungs, for which the medical
term is mesothelioma of the
pleura. This has been attribut-
ed to one particular variety
‘of asbestos, known as blue
asbestos.
_ Coal dust produces a spe-
cial type of damage to the
lungs. Because of the dusty
‘nature of mining and the large
numbers exposed, more cases
-of pneumoconiosis arise in
many industrialised countries
from this cause than from any
“other.
- The effect of dust on the
‘lung depends on four factors.
Mm addition to the chemical
nature of the dust, these are
the particle size, the concen-
tration and the duration of
exposure.

_PUST CLOUDS

1

Large particles are trapped
on the moist surfaces and the
specialised lining of the upper
respiratory passages. Only the
smaller particles can get down
into the substance of the lung.
‘Any dust cloud consists of
particles of many different
‘sizes and it is therefore neces-
Sary to measure the propor-
.tion of small particles in dust
clouds. Instruments have been
which imitate the

function of the body by dis-
carding the larger particles
and reeording only those
small enough to be breathed.

¥
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i

have therefore been designed
to measure dust concentra-
tions, and these are used by
inspectors to check samples of
the air in coal mines and other
places where industrial dust
is a hazard. It is also fairly
obvious that the more regular
and continuous the exposure
the sooner are malignant ef-
fects produced. Exposure for
short periods usually entails
little risk of ultimate lung
damage.

Where a worker is showing
the effects of dust the best
that can-be done is to remove
him from further exposure.
In many cases the disease is
arrested if this is done. In
others, especially where silica
or asbestos are involved, the
disease progresses just the
same, but not as rapidly as it
would have done had expos-
ure continued. From the med-
ical point of view, therefore,
every effort should be made
to recognize the disease at
the earliest point of time.

From the technical view-
point, measures should be de-
vised to eliminate the risks of
dust inhalation. Methods of
prevention should be intro-
duced as early -as possible,
preferably at the design stage
of a factory or process.

FLINT DUST

Wherever possible a harm-
less or less dangerous. sub-
stance should be used in place
of a dangerous material: By
this means the hazard can be
completely eliminated or
greatly reduced. The classic
example of this principle is
the elimination of the risk of
silicosis in the china industry
by the substitution of alumina
dust for flint dust.

For over 100 years the
workers concerned with the
bedding of china for firing had
suffered from a form of sili-
cosis known as potters’ rot. In
the early 1930s the suggestion
was made that alumina dust,
harmless to the lungs, would
be just as suitable for this
process. Tests proved this to
be true and in 1947 the use
of flint dust for this process
was prohibited by law in the
United Kingdom.

DEAD BY 40

Another example of suc-
cessful substitution is the re-
plecement of sandstone grind-
ing wheels by wheels made of
synthetic abrasives such as
carborundum. In the early
years of the cutlery industry,
knife and fork grinders gen-
erally died before the age of
40 of grinders’ phthisis, Today
the use of synthetic grinding
wheels has made the occupa-
tion safe from pneumoconio-
sis.

Shot blasting has taken the
place of sand blasting of
metal. Dextrin is used instead
of silica flour as a parting
powder in the foundry indus-
try. Olivine sand has been
used in some foundries as a

ing medium in place of

casting
silica sand. Felspar and pum-

ice have taken the place of
silica dust in kitchen abrasive
powders.

Unfortunately the practical
apvlications of the principle of
substitution are limited. Too
often the danger comes not
from a material used in the
manufacturing process, for
which a substitute may be
sought, but in the material
which is being produced. Coal
and asbestos are obvious ex-
amples. Reliance must there-
fore be placed on a combina-
tion of other methods in most
industries.

Mechanical handling is the
most effective of these. Me-
chanisation and automation of
processes reduce the number
of persons exposed to dust
and usually minimise the es-
cape of dust into the atmo-
sphere. The fewer persons in-
volved in the process the eas-
ier it is to apply control mea-
sures to the points where dust
may arise or to provide per-
sonal protection for the indi-
viduals concerned. Modern
foundries are using this prin-
ciple extensively.

VENTILATION

Many of the mechanised
handling systems are com-
bined with the method of en-
closure. This is simply an ar-
rangement by which the parts
to be handled — castings in a
foundry for example — are
cut off from the atmosphere

in a tunnel or other enclosure
during most of their journey

along the production line, only
emerging into the open where
handling is nécessary. Enclo-
sure in turn is often combined
with exhaust ventilation on
the basis that the more the
process is enclosed the more

effectively can exhaust ven-
tilation be applied.

Of all the methods of con-
trolling dust, exhaust ventila-
tion is in fact the most com-
monly used, either alone or
in combination with enclosure
and mechanisation. Unfortun-
ately it tends to be used bad-
ly in many cases. Ideally it
should be applied to the point
of origin of the dust and is

progressively less efficient the
further it is away from the

source. It has been success-

fully applied to carding en-
gines in the cotton industry
and to grinding wheels and
fettling chisels in the foundry
industry.

The design and balance of
exhaust ventilation systems is
a skilled engineering task
which cannot be left to chance
or rule of thumb as it fre-
quently is. Where a number
of machines are connected to
the system the total load must
be carefully calculated; the
addition of new machines
often upsets the balance of
ventilation unless the problem
is dealt with by the ventilat-
ing engineer.

WET SAWDUST.

The reduction of dust by
the use of water or wet saw-
dust is a familiar method of
dust control in daily domestic
use, but there are many so-
phisticated applications of this
principle, especially valuable
where ventilation is difficult
or impossible. For example,
where flint is still used in the
pottery industry in earthen-
ware and dust tile manufac-
ture it is conveyed to the pot-
tery as a suspension in water
known as slop flint instead of,
as in the past, in the dry form.

Water sprays are used in
coal mines to control dust on
conveyor belts and to reduce
dust at coal cutting opera-
tions. Drilling operations can
be carried out with a built-in
water infusion system which
prevents any dust being pro-
duced. Similar techniques are
used in gold mining and in
tunnelling. In the asbestos in-
dustry wet methods are used
to prevent dust arising during
spinning and weaving.

DEFENCE LINE

Where all else fails, the
worker himself must be pro-
tected. This is the last line of
defence. As far as possible,
dust control measures should
be applied to the tool or the
process, but there are special
maintenance jobs and some
highly specific operations such
as shot blasting where per-
sonal protection is the only
practical method.

The dust respirator, in
which the air passes through

a filter of resinated wool, is
in common use but its value
is limited. Much depends on
the fit of the respirator on the
face. These appliances are in
general so uncomfortable and
unreliable that men should
not be expected to wear them
for more than half an hour
at a time.

EXAMINATION |

Personal protection includes
the medical examination of
workers exposed to dust. The
use of periodic X-ray and
lung function tests enables the
physician to detect the earliest
signs of disease, especially in
individuals who are unusually
susceptible to the effects. of
dust. He can then advise such
persons of the potential dan-
gers of continuing in the same ~
employment. But medical ex-
amination is no substitute for
efficient dust control.

‘PAST PLAGUES

The great plagues of the
past are gradually being
brought under control. Mala-
ria, smallpox, and typhus are
yielding to eradication
schemes in many parts of the
world.

Pneumoconiosis is a man-
made plague which can also
be eradicated by the applica-
tion of techniques which are
already well known. That
they fail to be applied is part-
ly due to ignorance on the
part of employers and trade
unions, partly to the lack of
effective legislation by gov-
ernments and partly to the
absence of sufficient trained
industrial hygiene personnel,
but they are also neglected
because of the fear that pre-
cautions of the necessarily
high standards are too costly.
It is true that the application
of dust suppression measures
to existing plant is often very
expensive, but if these pre-
cautions are designed into the
process from its inception any
extra cost is marginal.

In either case, against the -
cost of installation must be
set the catalogue of death and
disability which is the pen-
alty for failing to take effec-
tive measures against the in-
halation of dust.