Silica Dust
Construction work that involves exposure to airborne sand
and rock dust can expose employees to crystalline silica.
Exposure to crystalline silica has been shown to cause silicosis,
a lung disease. Although most cases of silicosis develop after
years of exposure, instances of extremely high exposure have
resulted in illness and even death in a matter of weeks. Hazardous
activities include abrasive blasting with sand and loading,
dumping, chipping, hammering, cutting, and drilling of rock,
sand, or concrete.
Airborne permissible exposure limits (PELs) are established
for several different forms of crystalline silica. These limits
range from 0.05 to 0.1 mg/m3 of respirable dust, expressed
as an 8hour TWA (see Table AC-1 of
5155).
Generally during work on materials, such as rock or concrete,
that contain a significant amount of silica (20% or greater),
continuous exposure to a visible cloud of dust will probably
result in levels of exposure that exceed the PELs. However,
in some cases the PELs can be exceeded even when there is
no visible cloud of dust. Before beginning work that could
expose employees to crystalline silica, employers must comply
with the following requirements:
A. Employers must measure and control employees’ exposure
to airborne contaminants.
5155(c),(e)
B. Employers must train employees in the hazards of crystalline
silica exposure and the measures to control risk, including
proper use of respirators when required.
5144,
5194
C. Operations in which employees may be repeatedly exposed
to rock dust or sand should be evaluated by a qualified
industrial hygienist. Assistance can be obtained from the
Cal/OSHA Consultation Service.
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