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.