SILICA IN THE WORKPLACE
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365-AXJ-01-iGDO © 2020, Workplace Safety & Prevention Services (WSPS)
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4. Limits of Exposure Established In The Regulation Respecting Silica
Silica means crystalline silica in a respirable form. Respirable means that size fraction of the airborne
particulate deposited in the gas-exchange region of the respiratory tract and collected during air
sampling with a particle size-selective device that:
a) Meets the American Conference of Government Industrial Hygienists (ACGIH) particle
size-selective criteria; and
b) Has the cut point of 4 microns at 50 per cent collective efficiency.
The time-weighted average exposure of a worker to airborne silica must be reduced to the lowest
practical level and in any event must not exceed:
Cristobalite (CAS# 14464-46-1), 0.05 mg/m
3*
Quartz (CAS # 14808-60-7), 0.1 mg/m
3*
Tripoli (CAS # 1317-95-9), 0.1 mg/m
3*
5. Responsibilities Under The WHMIS Regulation (R.R.O. 1990, Reg. 860)
WHMIS or the Workplace Hazardous Materials Information System is a regulated system across
Canada designed to ensure that workers know and understand the hazards of materials to which they
are exposed at work. The system covers controlled products (products that meet federal criteria for
certain classes of materials including toxic materials). The Occupational Health and Safety Act and the
WHMIS Regulation place duties on employers with respect to these products and these duties apply in
workplaces where silica is used. Employers must ensure that:
*The CAS (Chemical Abstracts Service) Registry Number is the universally recognized unique identifier of chemical
substances and is often found on packaging and safety data sheets.
