Crystalline silica particles as they appear under the polarized

light microscope. Image by William Jones, Ph.D.
SILICOSIS IN SANDBLASTERS SILICOSIS IN SANDBLASTERS

A Case Study Adapted for

Use in U.S. High Schools

SAFER ! HEALTHIER ! PEOPLETM
DISCLAIMER

Mention of any company or product does not constitute

endorsement by NIOSH.

ORDERING INFORMATION

To receive documents or other information about occupational safety and health topics, contact the National Institute for Occupational Safety and Health (NIOSH) at

NIOSH—Publications Dissemination

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Telephone: 1–800–35–NIOSH (1–800–356–4674)

Fax: 513–533–8573

E-mail: pubstaft@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh

DHHS (NIOSH) Publication Number 2002–105

June 2002

This document is in the public domain

and may be freely copied or reprinted.
NIOSH Case Study in Occupational Epidemiology

SILICOSIS IN SANDBLASTERS

A Case Study Adapted for Use

in U.S. High Schools

GOAL—To learn about epidemiology by studying an occupational hazard, a disease associated with the hazard, and the

methods for preventing the disease. Epidemiology is the study

of why and how a disease occurs and spreads in populations.

The purpose of epidemiology is to prevent and control disease

by identifying its causes and the methods for control. Occupational epidemiology is the study of disease or injury related

to work activities and the worksite.

Congress passed the Occupational Safety and Health Act in

1970 to assure every working man and woman in the United

States a safe and healthful workplace. Although we have

made progress since that time, serious problems still occur

and result in illness, injury, disability, and death. Preventing

these tragedies requires the cooperation and effort of everyone concerned.

More than 2 million U.S. workers are potentially exposed

to dusts containing crystalline silica. Prolonged inhalation

of silica-containing dusts puts these workers at risk for the

disease silicosis—a nodular fibrosis of the lungs that causes

shortness of breath. More than 100,000 U.S. workers are in

high-risk occupations such as sandblasting. Most sandblasters

work in construction and shipbuilding. Workers may be exposed to crystalline silica in many other industries, including

surface and underground mining, pottery, drywall hanging,

glassmaking, foundry work, quarry work, work with sandblasting materials, agriculture, and automotive repair.

1
After completing this case study, the student should be able to

do the following:

• Use occupational health and epidemiologic approaches

to solve real-life problems

• Understand how public health and occupational health

professionals work together to solve occupational health

problems

• Recognize that silicosis (even in only one worker) is a

serious occupational disease requiring that the workplace be checked for dangerous conditions and that other

workers be checked for silica-related disease

• Assess hazards that place workers at risk for silicosis

• Describe methods for preventing silicosis

GLOSSARY

Abrasive blasting—A process for cleaning metal and other surfaces using material in a high-pressure stream. The material is

blasted against a surface to remove paint or contaminants. Ifsilica sand is used as the material, this process is called sandblasting.

Accelerated silicosis—A silicosis that develops 5 to 10 years

after exposure to high concentrations of crystalline silica.

Acute silicosis—A silicosis with symptoms that can develop a

few weeks to 5 years after exposure to very high concentrations

of crystalline silica. The term “acute” usually refers to a short

but severe illness. In acute silicosis, the time between exposure

and severe illness is shorter than in accelerated or chronic

silicosis.

Air monitoring—The use of specialized equipment to measure

types of pollutants and their concentrations in the atmosphere.

2
Automation—The replacement of human or animal labor by

machines. One example is the use of robots or remote-controlled

equipment for lifting and transporting materials.

Biopsy—The removal and examination of tissue, cells, or fluids from a living body for diagnosis of disease.

Chronic silicosis—A silicosis that develops after 10 or more

years of exposure to low concentrations of crystalline silica.

Crystalline silica—The crystalline form of silica; a mineral

made of silicon and oxygen (SiO2) that is naturally abundant in

the earth’s crust. In its crystalline form (primarily as quartz,

tridymite, or cristobalite), silica may be harmful if inhaled.

Cyanosis—A bluish or purplish discoloration due to inadequate oxygen concentration in the blood. This discoloration is

most often seen in the skin, but it occurs in other body systems.

Engineering controls—Methods of controlling worker exposures to hazardous agents by adjusting the source or reducing

the amount released in the workplace. Examples include a

change in process, substitution of less harmful job activities or

materials, isolation, and ventilation. Engineering controls are

the preferred method for targeting worksite hazards.

Epidemiology—The study of why and how a disease occurs

and spreads in populations.

Fibrosis—Scarring of the lungs due to breathing harmful dusts

or chemicals such as crystalline silica. As the disease develops,

the lungs begin to stiffen and become less flexible, making

breathing more difficult.

Fit testing—A procedure for checking to see that a respirator

fits properly and does not allow pollutants to be inhaled.

3
Industrial hygiene—The applied science of recognizing, evaluating, and controlling factors in the workplace that may cause

illness or injury for workers.

Local exhaust ventilation—An air movement system for capturing pollutants in the air directly where they are produced and

carrying them away before they can spread throughout the

work area.

Material safety data sheet (MSDS)—A written summary of

important safety and health information about a chemical or

substance. Manufacturers must supply the MSDS for each

hazardous agent purchased. Employers must make the MSDS

available to employees for each hazardous agent used.

Mine Safety and Health Administration (MSHA)—A Federal

agency within the U.S. Department of Labor. MSHA develops

and enforces regulations for workplace safety and health in the

mining industry.

National Institute for Occupational Safety and Health

(NIOSH)—A Federal occupational safety and health research

agency within the Centers for Disease Control and Prevention,

U.S. Department of Health and Human Services. NIOSH also

communicates safety and health information to workers, employers, and government agencies such as the Occupational

Safety and Health Administration (OSHA).

Occupational Safety and Health Administration (OSHA)—A

Federal agency within the U.S. Department of Labor. OSHA

develops and enforces regulations for workplace safety and

health.

Outbreak—A sudden increase in the number of new cases of a

disease in a geographic area.

Particulate—A particle or small object made of a solid or liquid material.

4
Pneumonia—A lung disease caused by infection or irritants

and characterized by inflammation.

Pneumoconiosis—A lung disease caused by inhaling hazardous

dusts.

Protective clothing—Any clothing designed or intended to be

worn as protection from exposures to harmful agents such as

chemicals.

Pulmonary edema —An abnormal accumulation of fluid in the

lungs.

Respirable particles—Airborne particles within a size range

that allows them to be inhaled and to penetrate deeply into the

lungs.

Respirator—A device worn over the mouth and nose or entire

head to protect the user from inhaling harmful agents.

Respiratory protection program—A plan established by an

employer to protect workers from inhaling harmful agents in

the workplace. The elements of a respiratory protection program

are described under Question 6 in the text.

Sandblasting—A process for cleaning metal and other surfaces using sand in a high-pressure air stream. The sand is

blasted against a surface to remove paint or contaminants. This

process is also called abrasive blasting.

Silica sand—The fine particles from ground rock containing a

high content of crystalline silica.

Silicosis—A nodular fibrosis of the lungs and shortness of

breath caused by prolonged inhalation of silica-containing dusts.

5
Silicotic nodule—A mass of tissue that is a reaction of the body

to crystalline silica particles.

Source controls—Any engineering change made to eliminate

or reduce exposures at the point where the hazard is generated

(for example, enclosing equipment, putting up a barrier to the

equipment, and using wet methods, dust collection systems,

and substitution).

Substitution—The removal of a harmful agent from a process

and its replacement with an agent that is less harmful to health.

Supplied-air respirator—A protective device that delivers

fresh (uncontaminated) air to the user through a supply hose

connected to the facemask or enclosure.

Wet methods—The use of water or another suitable liquid with

industrial processes (cutting, sanding, grinding) to reduce dust

concentrations in the air.

Work practices—The procedures followed by employers and

workers to control hazards in the workplace (for example, use

of wet methods to control dust).

PART I. CASE STUDY

How did epidemiologists find out what

caused a silicosis outbreak in Texas?

In November 1988, a doctor in Texas reported three cases of

silicosis to his local health department. These workers went to

the doctor because they were becoming very short of breath.

All three men worked at a facility where they sandblasted

oil-field drilling pipes. One of the workers (aged 34) died of

acute silicosis. The doctor reported the cases to the health

6

Question 1.
department because silicosis is a very serious occupational disease. The doctor knew that the facility where these people

worked might be hazardous. The doctor wanted the facility

to be checked by the local health department to protect other

people from developing silicosis. Recognition of silicosis usually signals a serious problem in the workplace.

The county health department and the Texas Department of

Health contacted other local doctors and identified seven

more workers who had suffered from silicosis since 1985.

Thus the health departments identified a total of 10 workers

who had been diagnosed with silicosis. Epidemiologists

from the Texas Department of Health conducted an investigation of the workers with silicosis. The investigators reviewed

personal and occupational histories from each worker who

had been diagnosed with silicosis. They reviewed lung biopsy

reports and inspected the facility for hazardous agents. The

workers’ chest X-rays were examined for lung diseases.

Each of the 10 workers had been exposed to crystalline silica at

the workplace. Their chest X-rays were all abnormal and

showed pneumoconiosis. Nine of the workers had abnormal

lung biopsy reports of silicotic nodules or acute silicosis. The

workers’ ages ranged from 24 to 50 at the time of diagnosis.

Seven workers were under age 30.

All 10 workers had used sandblasting machines for periods of

18 months to 8 years (the average was 4.5 years). Nine workers

reported no silica exposure before working at the current site.

The other worker had sandblasted oil-field drilling equipment

for 3 years before working at the current site for 5 years. The

epidemiologists from the Texas Department of Health consulted with occupational safety and health experts (called industrial hygienists) to learn more about the industrial

processes that could have caused silicosis at this facility.

7
The sandblasting process at the facility used a blasting rod with

a sandblasting agent containing 20.5% crystalline silica sand.

The rod, which was connected to a high-pressure air supply

hose, was held by the worker and directed through the drilling

pipe. The abrasive silica sand from the rod was air-blasted

against the inner walls of the pipe. This process removed contaminants to create a cleaner, smoother interior surface for application of a protective plastic coating. Although the sandblasting operation was enclosed by blasting cabinets connected to

exhaust systems, the cabinets were in poor condition and permitted clouds of dust to be released throughout the work area.

Workers stood inside booths intended to protect them from inhaling crystalline silica. However, the booths actually increased

the workers’ inhalation of crystalline silica by drawing their air

from surrounding areas with high silica contamination. Workers

then shoveled the used sandblasting mixture into the machinery for reuse.

In March 1989, air samples collected in the workers’ breathing

zones showed high concentrations of crystalline silica in the

sandblasting area.

PART II. UNDERSTANDING SILICOSIS

What is silica and what are the possible

dangers of working with silica?

Silica may be of several distinct types. For example, quartz is a

crystalline form of silica and is the most common mineral in the

earth’s crust. When rock containing quartz is chipped, hammered, drilled, crushed, loaded, hauled, or dumped, small particles of silica are released into the air and can be inhaled by

workers.

Silica sand containing quartz is used in sandblasting equipment to clean surfaces. The outsides of buildings and bridges

8

Question 2.
and the insides of storage tanks and pipes are some of the surfaces that are cleaned by sandblasting.

The silica sand used in sandblasting breaks into fine particles

that stay in the air (Figure 1). If these particles are small

enough to be inhaled deeply into the lungs, they are known

as respirable crystalline silica. Inhaling these fine silica particles causes more lung damage than inhaling larger particles.

This process causes rapid and severe forms of silicosis in

sandblasters.

Figure 1. Detailed microscopic view of silica particles

on a filter. (Scanning electron micrograph by

William Jones, Ph.D.)

What is silicosis?

When workers inhale crystalline silica, the lung develops scar

tissue around the silica particles. This process results in a lung

disease known as silicosis. As more lung tissue is damaged by

silica dust, breathing becomes more difficult, chest pain occurs, and death may result. Silicosis patients suffer shortness of

9

Question 3.
breath, fever, and cyanosis. Some patients are diagnosed incorrectly as having pulmonary edema, pneumonia, or other

lung diseases.

The three types of silicosis are as follows:

• Chronic silicosis, which occurs after 10 or more years of

exposure to low concentrations of crystalline silica.

• Accelerated silicosis, which occurs 5 to 10 years after

exposure to high concentrations of crystalline silica.

• Acute silicosis, which occurs a few weeks to 5 years

after exposure to very high concentrations of crystalline

silica.

10

QuesQuesHawk’s Nest Incident

Descriptions of chronic silicosis have been available

since the late 1800s. But acute silicosis first received

widespread public attention in 1936, when Congress

investigated reports of 1,500 cases of workers with

acute silicosis near the town of Gauley Bridge, West

Virginia. The incident has been called “America’s

worst industrial disaster.” The workers were hired to

tunnel through a mountain with a very high concentration of silica. As a result, the workers were exposed to

high concentrations of silica dust in the air while they

were working. More than 1,000 of these workers are

believed to have died from acute silicosis caused by

their silica exposure on this project. Almost no precautions were taken against inhalation of silica. These

events are described in the book The Hawk’s Nest Incident: America’s Worst Industrial Disaster, by Martin

Cherniak.
How many workers are exposed to

dusts containing crystalline silica?

More than 2 million U.S. workers are potentially exposed to

dusts containing crystalline silica. More than 100,000 of

them are in high-risk occupations, including sandblasting.

Most sandblasters work in construction and shipbuilding.

Workers may be exposed to crystalline silica in many other

industries, including surface and underground mining, pottery, drywall hanging, glassmaking, foundry work, quarry

work, work with sandblasting materials, agriculture, and automotive repair.

PART III. PREVENTION OF SILICOSIS

What fields of occupational health protect workers from occupational hazards?

Industrial hygiene is the science of recognizing, evaluating, and controlling hazards in the workplace and environment. Industrial hygiene practices protect workers from

hazards. Other professionals important for protecting

workers’ health include occupational health physicians and

nurses as well as engineers.

What practices are used to protect

workers from silicosis?

Industrial hygiene practices are used to protect workers from

silicosis and other workplace hazards. These practices include

the use of substitution, engineering controls, work practices,

respiratory protection, and air monitoring. Employers are

responsible for implementing these practices when they are

needed to provide safe and healthful workplaces.

11

Question 4.

Question 5.

Question 6.
Substitution

Crystalline Silica as a Blasting Material

The use of crystalline silica was banned for most

blast-cleaning operations in Great Britain in 1950

(Factories Act of 1949) and in other European countries in 1966. In 1974, NIOSH recommended that

silica sand be prohibited for use as an abrasive

blasting material and that less hazardous materials

be substituted for silica sand during abrasive blasting.

NIOSH has studied several abrasive agents that might be used

as substitutes for silica sand during sandblasting. Some of the

abrasives studied are steel grit, specular hematite, nickel slag,

copper slag, crushed glass, garnet, staurolite, olivine, and coal

slag. Most of these abrasives work as well as silica sand and

cost about the same or even less. However, the use of a substitute may have other adverse effects. Regardless of the type of

abrasive, NIOSH recommends the use of engineering controls,

work practices, respiratory protection, and air monitoring (all

described below) to reduce hazards to workers during sandblasting. Figure 2 illustrates good work practices and the proper

use of personal protective equipment for abrasive blasting.

Engineering Controls

Engineering controls are hazard controls designed into equipment and workplaces. Examples of engineering controls are

— automated equipment operated from an enclosed booth,

— enclosed blast-cleaning machines and cabinets,

— tools with dust collection systems, and

— local exhaust ventilation.

12
Engineering controls are sometimes called source controls

when they are designed to eliminate or reduce exposures at the

source.

Work Practices

Work practices are procedures followed by both employers and

workers to control hazards in the workplace. Examples of work

practices are

— wet drilling or sawing of silica-containing materials,

— showering and changing into clean clothing before

leaving work, and

— avoiding smoking, eating, and drinking in dusty areas.

13

Figure 2. Sandblaster using proper respiratory protection inside a ventilated booth. Note that the worker is supplied with two separate air

lines—one to supply fresh air for the worker to breathe and the

other to supply air for sandblasting.
Respiratory Protection

Respiratory protection prevents workers from inhaling pollutants. Appropriate respiratory protection equipment and programs should be provided whenever engineering controls and

work practices cannot keep concentrations of airborne silica at

or below safe limits.

Respirators—Workers can wear special protective equipment

called respirators to protect them from inhaling respirable crystalline silica. Respirators are a good option as protective equipment, but they should be used only when controls (such as

substitution, automation, enclosed systems, and local exhaust

ventilation) cannot keep exposures at or below safe limits.

Workers who perform sandblasting must use the type of respirator recommended by NIOSH for their particular job. Regardless of the abrasive used, NIOSH recommends a respirator that

provides a constant supply of clean air through a line that connects to a hood or helmet worn by the worker. The respirator

air line must be separate from the line that supplies air for blasting. This device is known as a type CE abrasive-blasting respirator operated in the continuous-flow mode.

Respiratory Protection Program—To make sure that respirators are used properly, the employer must establish a comprehensive respiratory protection program as required in the

OSHA respiratory protection standard of 1998 (see the NIOSH

Guide to Industrial Respiratory Protection for guidance). The

following are important elements of this standard:

• Periodic air monitoring

• Regular training of workers in respirator use

• Selection of proper NIOSH-approved respirators

14
• A medical determination of the worker’s ability to

perform the work while using a respirator

• Respirator fit testing

• Maintenance, inspection, cleaning, and storage of

respirators

The respiratory protection program should be evaluated

regularly by the employer.

Air Monitoring

Air-monitoring equipment measures air pollutants such as silica to assess worker exposure. Industrial hygienists and

air-sampling technicians perform air monitoring. The samples

from air monitoring are analyzed to identify concentrations and

types of pollutants in the air. The results of air monitoring for

crystalline silica are used to select and evaluate engineering

controls and respiratory protection. These air monitoring results are also compared with exposure limits that are required

or have been recommended on the basis of health studies of animals and humans. NIOSH, OSHA, and MSHA have exposure

limits for respirable crystalline silica. For more information

about these exposure limits, see Suggested Reading List and

Other Useful Resources in Question 8.

What else is done to detect and control silicosis in a workplace?

Medical exams should be offered to all workers who may be

exposed to respirable particles of silica. Each exam includes a

job history, a medical history, and a physical exam. The job

history questionnaire asks about all the jobs the worker has

had, all the materials worked with, and all protective equipment used. These exams should occur before job placement

15

Question 7.
or entry into a trade. Workers should continue to have

followup medical evaluations as well as careful monitoring of

their work and exposures.

What steps can employers take to prevent silicosis in workers who work

with crystalline silica?

1. Use abrasive blasting materials that are less hazardous than

those containing more than 1% crystalline silica. Because

substitute abrasives may also have toxic effects, NIOSH

recommends the use of engineering controls, work practices, and respiratory protection for all abrasive blasting,

regardless of the type of abrasive used.

2. Recognize situations in which silica dust may be generated; plan to eliminate or control dust at its source.

3. Inform workers about their exposures to crystalline silica

dust, the possible health effects of this dust, and the risk of

silicosis.

4. Establish effective programs for monitoring the exposure

of workers to crystalline silica dust. Conduct air monitoring to measure worker exposure and check that controls are

working properly.

5. Train workers about safe work practices to reduce exposure to crystalline silica. For example, workers should remove dust from equipment with a water hose instead of

compressed air. Use vacuums with high-efficiency particulate air filters (HEPA filters). Use wet sweeping instead of

dry sweeping.

6. Post warning signs to mark the boundaries of work areas

that may be contaminated with respirable crystalline silica.

16

Question 8.
7. Provide workers with material safety data sheets (MSDSs)

for silica, masonry products, alternative abrasives, and

other hazardous materials to which they may be exposed.

8. Provide workers with information about safe handling,

labeling, and storage of toxic materials.

9. Write all signs, labels, instructions, and other material for

workers in easy-to-read English and in any other languages

needed for workers’ understanding of the material.

10. Provide engineering controls such as containment methods (enclosed blast-cleaning machines and cabinets).

Provide equipment for wet drilling or wet sawing of

silica-containing materials. Make sure workers use tools

with dust collection systems. Use local exhaust ventilation to prevent release of dust into the air.

11. Provide appropriate respiratory protection for workers,

including NIOSH-certified respirators and a respiratory

protection program to ensure proper use and maintenance

of respirators.

12. Provide regular medical exams for workers who may be

exposed to respirable crystalline silica.

13. Provide either disposable protective clothes or protective

clothes that are laundered at the workplace.

14. Provide areas for workers to shower and change into clean

clothes before leaving the worksite. This practice prevents

contamination of other work areas, cars, and homes.

15. Report all cases of silicosis to state health departments and

to OSHA (1–800–321–6742) or MSHA (1–800–746–1553).

17
What steps can workers take to reduce exposure to silica and prevent

silicosis?

1. Use proper respiratory protection when engineering controls cannot keep silica exposures at or below safe limits.

2. Remove dust from equipment with a water hose instead of

compressed air. Use vacuums with HEPA filters. Use wet

sweeping instead of dry sweeping.

3. Change into disposable protective clothes at the worksite.

4. Shower and change into clean clothes before leaving the

worksite to prevent contamination of other work areas,

cars, and homes.

5. Do not eat, drink, use tobacco products, or apply cosmetics

in dusty areas.

6. Wash hands and face before eating, drinking, or smoking

outside dusty areas.

7. Do not park cars where they can be contaminated with silica

or other pollutants.

The personal hygiene habits mentioned above are important

because workers may take home silica and other harmful substances on their clothes, skin, hair, and automobiles. Exposure

to these substances may make other household members sick.

What additional information is available about preventing silicosis?

Additional information about preventing silicosis is available

in the publications on the following Suggested Reading List

and from the Other Useful Resources listed at the end of this

18

Question 9.

Question 10.
document. Note that the NIOSH documents on this list are

available at the Web site printed at the end of each reference.

Single copies of NIOSH documents are also available free

from NIOSH at

1–800–35–NIOSH (1–800–356–4674)

Fax: 513–533–8573

E-mail: pubstaft@cdc.gov

SUGGESTED READING

Cherniak M [1986]. The Hawk’s Nest incident: America’s worst

industrial disaster. New Haven, CT: Yale University Press.

CPWR [1999]. Silica in sandblasting and rock drilling: hazard

alert. Washington, DC: The Center to Protect Workers’ Rights.

DiNardi SR, ed. [1997]. The occupational environment—its

evaluation and control. Fairfax, Virginia: American Industrial

Hygiene Association.

NIOSH [1987]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human

Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health,

DHHS (NIOSH) Publication No. 87–116 (full text of document is available at www.cdc.gov/niosh/87–116.html).

NIOSH [1992]. NIOSH Alert: request for assistance in preventing silicosis and deaths from sandblasting. Cincinnati, OH:

U.S. Department of Health and Human Services, Public Health

Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication

No. 92–102 (full text of document is available at

www.cdc.gov/niosh/92–102.html).

19
NIOSH [1996]. NIOSH Alert: request for assistance in preventing silicosis and deaths in construction workers. Cincinnati,

OH: U.S. Department of Health and Human Services, Public

Health Service, Centers for Disease Control and Prevention,

National Institute for Occupational Safety and Health, DHHS

(NIOSH) Publication No. 96–112 (full text of document is

available at www.cdc.gov/niosh/consilic.html).

NIOSH [1997]. Construction workers: it’s not just dust!

Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health,

DHHS (NIOSH) Publication No. 97–101 (full text of document

is available at www.cdc.gov/niosh/1997–101. html).

NIOSH [1997]. NIOSH pocket guide to chemical hazards.

Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and

Prevention, National Institute for Occupational Safety and

Health, DHHS (NIOSH) Publication No. 97–140 (full text of

document is available at www.cdc.gov/niosh/npg/npg.html).

NSC [1996]. Fundamentals of industrial hygiene. 4th ed. Chicago, IL: National Safety Council.

Parkes WR [1994]. Occupational lung disorders. 3rd ed. Oxford, England: Butterworth-Heinemann, Ltd.

OTHER USEFUL RESOURCES

The Center to Protect Workers’ Rights (CPWR)

Telephone: 1–301-578-8500

Web site: www.cpwr.com

Mine Safety and Health Administration (MSHA)

Toll-free telephone: 1–800–746–1553

20
Other telephone: 1–703–235–1452

Web site: www.msha.gov

National Institute for Occupational Safety and Health (NIOSH)

Toll-free telephone: 1–800–35–NIOSH (1–800–356–4674)

Web site: www.cdc.gov/niosh

Occupational Safety and Health Administration (OSHA)

Toll-free telephone: 1–800–321–OSHA (1–800–321–6742)

Web site: www.osha.gov

ACKNOWLEDGMENTS

This module was prepared by NIOSH staff. The principal

author was Bonita D. Malit, M.D., M.P.H. Thomas J. Lentz,

Ph.D., assisted with the industrial hygiene sections. Gregory

Loos, Ph.D., and Faye L. Rice also contributed to this module.

Susan Feldmann and Anne C. Hamilton provided editorial review and Susan Kaelin provided design and layout of the

document.

21