occupational exposure limit at a fed-
eral level is 0.025mg/m 3 .

Exposure needs to be monitored
and the health of workers kept under
surveillance to ensure levels are not
harmful. Visual sight is not effective to
determine dangerous levels – as by
the time you observe a dust cloud, lev-
els are already likely to be far in ex-
cess of the WEL of 0.1mg/m 3 .

What happens to those exposed?
Unlike asbestos, where it may take
anywhere between 10 to 50 years to
manifest, symptoms for silicosis can
start within extremely short periods of
time. Individual susceptibility is based
on a number of factors including the
amount of dust, its size, respiratory
protective equipment worn, the indi-
vidual’s overall health status, and
whether the person is a smoker - to
name but a few.

Silica dust is one of the world’s
most significant causes of occupa-
tional disease with an estimated
46,000 deaths globally in 2013.

Occupational respiratory diseases –
Silicosis The name silicosis is derived from
the Latin word Silex or flint. However,
it has been known under many other
previous names including ‘grinder’s
asthma’, ‘potters rot’ and ‘miner’s ph-
thisis’. Its recognition goes back to
the time of the Greeks and Romans,
who spoke of respiratory problems
from breathing in dust.

With the dawn of industrialization,
many new devices were introduced
including pneumatic hammer drills in
1897 and sandblasting in 1904, which
led to a steady rise in silicosis preva-
lence. While we don’t have specific
data for Canada overall, these are
some numbers from other countries:
Silicosis is defined as an occupa-
tional lung disease classed as a pneu-
Healthy Lung
Early stages
Late stages
Above image shows the progressive worsening of lung tissue in black lung which
is also a form of pneumoconiosis like Silicosis
moconiosis and is marked by inflam-
mation and scaring of the upper lobes
of the lungs in the form of nodular le-
sions. In acute (short term, severe or sud-
den) form the symptoms are typically
bluish skin, breath shortness, cough
and fever. It is not uncommon for this
to be misdiagnosed as pulmonary
oedema (water on the lungs), pneu-
monia or Tuberculosis. Symptoms can
continue to develop even after expo-
sure has stopped.

Exposure to RCS dust can also
cause: • chronic bronchitis;
• lung cancer;
• pulmonary fibrosis;
• rheumatoid arthritis;
• scleroderma;
• systemic lupus erythematosus;
• autoimmune antibodies;
• and a variety of other conditions
associated with exposure.

Based on the above conditions it is
conceivable many persons exposed to
RCS dust may go on to develop other
conditions other than silicosis.

Industrial Countries
UK EU
Germany France
Australia Japan
USA 800 die annually from lung cancer caused with RCS with 900 new
cases of lung cancer diagnosed as a result of RCS exposure
7000 cancers of lung cancer are due to RCS
400 new cases annually (1990’s)
300 cases annually
1,010 cases predicted
1,000 cases annually
3,600-7,300 cases annually / 2m exposed; 10% at risk
Developing Countries
China Pneumoconiosis
India Brazil
Latin America
Columbia South America
5000 annual deaths with 20m exposed with
72% of all work-related diseases
10m exposed to RCS
6.6m exposed
37% prevalence amongst miners
1.8m workers at risk
1m former miners with silicosis. 30-50% prevalence in some industries
Type of Silicosis
Exposure Latency before symptoms develop
Acute Silicosis*
Heavy exposure over short periods
2 weeks - 5 yrs.

Accelerated Silicosis**
High exposure over a period of time
5 – 10 yrs.

Chronic Simple Silicosis
Relatively low to moderate exposure
over a long period of time
10+ yrs.

14 – Winter 2017 — The Canadian Design and Construction Report




So how can we work safely without
being harmed?
We know that RCS is harmful to
health and also know that there is a
level that is considered safe. If the
threat of exposure to RCS cannot be
eliminated altogether then there are a
few control measures that may work.

It is estimated that silica related lung
cancer could drop to 100 a year (cur-
rently circa 800 in the UK) if more legal
compliance is instigated, including the
points raised below.

To ensure compliance with your
various legislative requirements you
should follow the local rules. Here we
will adopt guidelines from the UK
Health & Safety Executive based on
compliance with the Control of Sub-
stances Hazardous to Health Regula-
tions 2002 (COSHH) requirements:
— Assess
— Control
— Review
Assess (the risks)
Assess the risks linked to the work
and materials.

High dust levels are caused by one
or more of the following:
Task – high-energy tools like cut-off
saws, grinders and grit blasters pro-
duce a lot of dust in a very short time;
Work area – the more enclosed a
space, the more the dust will build up.

However, do not assume that dust lev-
els will be low when working outside
with high-energy tools;
Time – the longer the work takes
the more dust there will be;
Frequency – regularly doing the
same work day after day increases the
risks Control (the risks)
For operatives tasked with specific
activities where RCS could become
airborne, options of using mechanical
equipment such as remote controlled
rock-breaker or other means to pro-
vide some degree of separation be-
tween the workers, can be used. In
some cases, the means can be as
simple as dousing with a water
stream and standing upwind. Other
techniques such as hydro-demolition
can be adopted and certainly from
safety and an environmental element,
can be beneficial in terms of dust sup-
pression but can introduce a number
of other hazards.

Use the following measures to
control the risk.

Stop or reduce the dust before
work starts, look at ways of stopping
or reducing the amount of dust you
might make. Use different materials,
less powerful tools or other work
methods. For example, you could use:
• The right size of building materials
so less cutting or preparation is
needed; • silica-free abrasives to reduce the
risks when blasting;
• a less powerful tool; or
• a different method of work alto-
gether. Control the dust
Even if you stop some dust this
way, you may do other work that
could still produce high dust levels.

In these cases, the most important
action is to stop the dust getting into
the air.

There are two main ways of doing
this: • Water – water damps down dust
clouds. However, it needs to be
used correctly.

This means enough water supplied
at the right levels for the whole time
that the work is being done. Just wet-
ting the material beforehand does not
work. • On-tool extraction – removes
dust as it is being produced. It is
a type of local exhaust ventilation
(LEV) system that fits directly onto
the tool. This ‘system’ consists of
several individual parts – the tool,
capturing hood, extraction unit
and tubing. Use an extraction unit
to the correct specification (i.e. H
(High) M (Medium) or L (Low)
Class filter unit).

Do not sweep. Use an industrial
vacuum cleaner with a high efficiency
HEPA filter. Don’t use a general com-
mercial vacuum.

Respiratory protective equipment
(RPE) Before considering RPE there are
various considerations ranging from
the type and duration of activities. It is
far easier and more efficient generally
speaking in using engineering con-
trols to protect a wider range of work-
ers than ill-fitting RPE which may give
a false sense of security and actually
endanger the lives of wearers.

Water or on-tool extraction may not
always be appropriate or they might
not reduce exposure enough. Often
respiratory protection (RPE) has to be
provided as well. You will need to
make sure that the RPE is:
• Adequate for the amount and type
The Canadian Design and Construction Report — Winter 2017 – 15