CAW National Council 4000
Occupational Health and Safety

Hazardous Substances:  Silica

Silica dust can create ill-health effects when inhaled.

Long-Term Effects

Long-term or excessive exposure creates a condition called silicosis. Silicosis is a scarring of the lungs which in turn causes
breathlessness. This is first only noticeable on exertion but as the disease progresses the worker may be breathless even at rest.
Silicotics run an increased risk of contracting tuberculosis as well as other lung infections. Silicosis of the lungs puts an increased
strain on the heart which may develop into heart failure.

Once a worker has developed silicosis no improvement is expected even though the worker is withdrawn from further exposure.
There is a tendency for the disease to progress in spite of no further exposure to silica. Cases of silicosis have been reported which
have developed several years after exposure to silica had ceased.


Substitution of less hazardous forms of silica having lower quartz content.
Enclose process
Local exhaust ventilation
General ventilation
Personal protective equipment


cristobalite 0.05 mg/m3
quartz 0.1 mg/m3
silica fused 0.1 mg/m3
tridymite 0.05 mg/m3
tripoli 0.1 mg/m3

NIOSH recommendation 0.05 mg/m3.

Source:  CAW Health, Safety & Environment Department