- OSHA & NIOSH Recommended Limits of Silica Dust Exposure
The NIOSH recommended
exposure limit (REL) for respirable crystalline silica is 0.05 mg/m^3
(50g/m^3) as a TWA for up to 10 hours/day during a 40-hour workweek
the following measures to reduce exposures to respirable crystalline
silica in the workplace and to prevent silicosis and deaths in construction
Recognize when silica dust may be generated and plan ahead
to eliminate or control the dust at the source.
Awareness and planning are keys to prevention of silicosis.
Do not use silica sand or other substances containing more
than 1% crystalline silica as abrasive blasting
less hazardous materials.
Use engineering controls and containment methods such as
blast-cleaning machines and cabinets, wet drilling, or wet
sawing of silica-containing materials to control the hazard and protect
adjacent workers from exposure.
Routinely maintain dust control systems to keep them in good
personal hygiene to avoid unnecessary exposure to other work site contaminants
such as lead.
Wear disposable or washable protective clothes at the work
Shower (if possible) and change into clean clothes before
leaving the work site to prevent
contamination of cars, homes, and other work areas.
Conduct air monitoring to measure worker exposures and ensure
that controls are providing adequate protection for workers.
9. Use adequate
respiratory protection when source controls cannot keep silica exposures below
the NIOSH REL.
Provide periodic medical examinations for all workers who
may be exposed to respirable crystalline silica.
Post warning signs to mark the boundaries of work areas contaminated
with respirable crystalline silica.
Provide workers with training that includes information about
health effects, work practices, and
Report all cases of silicosis to State Health Departments
for Silica Dust Exposure
current OSHA permissible exposure limit (PEL) for respirable crystalline
silica (quartz) is 100 µg/m3
as an 8-hour time-weighted average (TWA) [29 CFR**
1910.1000]. The NIOSH recommended exposure limit (REL) for respirable
crystalline silica is 50 µg/m3
as a TWA for up to 10 hours/day during a 40-hour workweek [NIOSH
1974b]. This REL is intended to prevent silicosis. However, evidence
indicates that crystalline silica is a potential occupational carcinogen
[NIOSH 1988a; IARC 1987; DHHS 1991], and NIOSH is reviewing the
data on carcinogenicity.
should be posted to warn workers about the hazard and specify any
protective equipment required (for example, respirators). The sample
sign in Figure 2 contains the information needed for a silica work
area where respirators are required.
Sample of warning
sign for work areas contaminated with crystalline silica.
for Silica Workers
receive training [29 CFR 1926.21] that includes the following:
about the potential adverse health effects of silica exposure
safety data sheets for silica, alternative abrasives, or other
hazardous materials [29 CFR 1926.59]
about obeying signs that mark the boundaries of work areas containing
about safe handling, labeling, and storage of toxic materials
[30 CFR 56.20012, 56.16004, 57.20012, 77.208]
about the importance of engineering controls, personal hygiene,
and work practices in reducing crystalline silica exposure
about the use and care of appropriate protective equipment (including
protective clothing and respiratory protection)
and Disease Reporting of Silicosis
encourages reporting of all cases of silicosis to the State health
departments and to OSHA or MSHA. To enhance the uniformity of reporting,
NIOSH has developed reporting guidelines and a surveillance case
definition for silicosis (see Appendix). This definition and these
guidelines are recommended for surveillance of work-related silicosis
by State health departments and regulatory agencies receiving reports
of cases from physicians and other health care providers [CDC 1990].
More Information see www.osha.gov