Crystalline Silica
What is crystalline silica?
Crystalline silica is a basic component of soil,
sand, granite, and many other minerals. Quartz
is the most common form of crystalline silica.
Cristobalite and tridymite are two other forms
of crystalline silica. All three forms may become
respirable size particles when workers chip, cut,
drill, or grind objects that contain crystalline silica.
What are the hazards
of crystalline silica?
Silica exposure remains a serious threat to
nearly 2 million U.S. workers, including more than
100,000 workers in high risk jobs such as abrasive
blasting, foundry work, stonecutting, rock drilling,
quarry work and tunneling. The seriousness of
the health hazards associated with silica exposure
is demonstrated by the fatalities and disabling
illnesses that continue to occur in sandblasters and
rockdrillers. Crystalline silica has been classified
as a human lung carcinogen. Additionally, breathing
crystalline silica dust can cause silicosis, which
in severe cases can be disabling, or even fatal.
The respirable silica dust enters the lungs and
causes the formation of scar tissue, thus reducing
the lungs’ ability to take in oxygen. There is no
cure for silicosis. Since silicosis affects lung function,
it makes one more susceptible to lung infections
like tuberculosis. In addition, smoking causes
lung damage and adds to the damage caused by
breathing silica dust.
What are the symptoms of silicosis?
Silicosis is classified into three types:
chronic /classic, accelerated, and acute.
Chronic/classic silicosis, the most common,
occurs after 15–20 years of moderate to low
exposures to respirable crystalline silica. Symptoms
associated with chronic silicosis may or may not be
obvious; therefore, workers need to have a chest
x-ray to determine if there is lung damage. As the
disease progresses, the worker may experience
shortness of breath upon exercising and have clinical
signs of poor oxygen/carbon dioxide exchange.
In the later stages, the worker may experience
fatigue, extreme shortness of breath, chest pain,
or respiratory failure.
Accelerated silicosis can occur after 5–10
years of high exposures to respirable crystalline
silica. Symptoms include severe shortness of
breath, weakness, and weight loss. The onset of
symptoms takes longer than in acute silicosis.
Acute silicosis occurs after a few months
or as long as 2 years following exposures to
extremely high concentrations of respirable
crystalline silica. Symptoms of acute silicosis
include severe disabling shortness of breath,
weakness, and weight loss, which often leads
to death.
Where are construction workers
exposed to crystalline silica?
Exposure occurs during many different
construction activities. The most severe exposures
generally occur during abrasive blasting with sand
to remove paint and rust from bridges, tanks,
concrete structures, and other surfaces. Other
construction activities that may result in severe
exposure include: jack hammering, rock/well
drilling, concrete mixing, concrete drilling, brick and
concrete block cutting and sawing, tuck pointing,
tunneling operations.
Where are general industry employees
exposed to crystalline silica dust?
The most severe exposures to crystalline silica
result from abrasive blasting, which is done to clean
and smooth irregularities from molds, jewelry,
and foundry castings, finish tombstones, etch or
frost glass, or remove paint, oils, rust, or dirt form
objects needing to be repainted or treated. Other
exposures to silica dust occur in cement and brick
manufacturing, asphalt pavement manufacturing,
china and ceramic manufacturing and the tool and
die, steel and foundry industries. Crystalline silica
is used in manufacturing, household abrasives,
adhesives, paints, soaps, and glass. Additionally,
crystalline silica exposures occur in the maintenance,
repair and replacement of refractory brick
furnace linings.
In the maritime industry, shipyard employees
are exposed to silica primarily in abrasive
blasting operations to remove paint and clean
and prepare steel hulls, bulkheads, decks, and
tanks for paints and coatings.
How is OSHA addressing
exposure to crystalline silica?
OSHA has an established Permissible Exposure
Limit, or PEL, which is the maximum amount of
crystalline silica to which workers may be exposed
during an 8-hour work shift (29 CFR 1926.55,
1910.1000). OSHA also requires hazard
2002
This is one in a series of informational fact sheets highlighting
OSHA programs, policies, or standards. It does not impose
any new compliance requirements. For a comprehensive list of
compliance requirements of OSHA standards or regulations,
refer to Title 29 of the Code of Federal Regulations. This information
will be made available to sensory-impaired individuals
upon request. The voice phone is (202) 693–1999. See also
OSHA’s website at www.osha.gov.
communication training for workers exposed
to crystalline silica, and requires a repirator
protection program until engineering controls are
implemented. Additionally, OSHA has a National
Emphasis Program (NEP) for Crystalline Silica
exposure to identify, reduce, and eliminate health
hazards associated with occupational exposures.
What can employers/employees
do to protect against exposures
to crystalline silica?
¦ Replace crystalline silica materials with safer
substitutes, whenever possible.
¦ Provide engineering or administrative controls,
where feasible, such as local exhaust ventilation,
and blasting cabinets. Where necessary to reduce
exposures below the PEL, use protective
equipment or other protective measures.
¦ Use all available work practices to control
dust exposures, such as water sprays.
¦ Wear only a N95 NIOSH certified respirator,
if respirator protection is required. Do not
alter the respirator. Do not wear a tight-fitting
respirator with a beard or mustache that prevents
a good seal between the respirator and the face.
¦ Wear only a Type CE abrasive-blast
supplied-air respirator for abrasive blasting.
¦ Wear disposable or washable work clothes
and shower if facilities are available. Vacuum
the dust from your clothes or change into
clean clothing before leaving the work site.
¦ Participate in training, exposure monitoring,
and health screening and surveillance
programs to monitor any adverse health
effects caused by crystalline silica exposures.
¦ Be aware of the operations and job tasks creating
crystalline silica exposures in your workplace
environment and know how to protect yourself.
¦ Be aware of the health hazards related to
exposures to crystalline silica. Smoking adds
to the lung damage caused by silica exposures.
¦ Do not eat, drink, smoke, or apply cosmetics
in areas where crystalline silica dust is present.
Wash your hands and face outside of dusty
areas before performing any of these activities.
¦ Remember: If it’s silica, it’s not just
dust.
How can I get more information
on safety and health?
OSHA has various publications, standards,
technical assistance, and compliance tools to
help you, and offers extensive assistance through
workplace consultation, voluntary protection
programs, strategic partnerships, alliances, state
plans, grants, training, and education. OSHA’s
Safety and Health Program Management
Guidelines ( Federal Register 54:3904-3916,
January 26, 1989) detail elements critical to the
development of a successful safety and health
management system. This and other information
are available on OSHA’s website.
¦ For one free copy of OSHA publications,
send a self-addressed mailing label to OSHA
Publications Office, 200 Constitution Avenue
N.W., N-3101, Washington, DC 20210; or
send a request to our fax at (202) 693–2498,
or call us toll-free at (800) 321–OSHA.
¦ To order OSHA publications online at
www.osha.gov, go to Publications and
follow the instructions for ordering.
¦ To file a complaint by phone, report an
emergency, or get OSHA advice, assistance,
or products, contact your nearest OSHA office
under the U.S. Department of Labor listing in
your phone book, or call toll-free at (800)
321– OSHA (6742). The teletypewriter
(TTY) number is (877) 889–5627.
¦ To file a complaint online or obtain more
information on OSHA federal and state
programs, visit OSHA’s website.
This is one in a series of informational fact
sheets highlighting OSHA programs, policies,
or standards. It does not impose any new
compliance requirements. For a comprehensive list
of compliance requirements of OSHA standards
or regulations, refer to Title 29 of the Code of
Federal Regulations. This information will be made
available to sensory-impaired individuals upon
request. The voice phone is (202) 693–1999.
See also OSHA’s website at www.osha.gov. |
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