Unified Agenda - Table of Contents| Title: Occupational Exposure
to Crystalline Silica Abstract: Crystalline silica is a
significant component of the earth's crust, and many workers in
a wide range of industries are exposed to it, usually in the
form of respirable quartz or, less frequently, cristobalite.
Chronic silicosis is a uniquely occupational disease resulting
from exposure of employees over long periods of time (10 years
or more). Exposure to high levels of respirable crystalline
silica causes acute or accelerated forms of silicosis that are
ultimately fatal. The current OSHA permissible exposure limit
(PEL) for general industry is based on a formula recommended by
the American Conference of Governmental Industrial Hygienists
(ACGIH) in 1971 (PEL=10mg/cubic meter/(% silica + 2), as
respirable dust). The current PEL for construction and maritime
(derived from ACGIH's 1962 Threshold Limit Value) is based on
particle counting technology, which is considered obsolete.
NIOSH and ACGIH recommend a 50µg/m3 e