Worker Health Study Summaries

Research on long-term exposure

Industrial Sand Workers (Silica Exposure) (2)

2002

Study Background

On January 18, 2002, NIOSH sent the results of a study of industrial and workers from 18 different plants to each participant in the study. The study focused on the health effects of exposure to silica.

Why did NIOSH study industrial sand workers?

Industrial sand workers are exposed to silica, a dust thought to cause lung cancer, silicosis, kidney disease, and arthritis.

NIOSH wanted to find out if industrial sand workers have an increased risk of these diseases (or possibly any others) when compared with the U. S. general public.

Who was included in the NIOSH study?

NIOSH studied 4,626 industrial sand workers from 18 plants in 11 different States.

NIOSH based their results on the personnel records of these 4,626 former and current industrial sand workers. The records were collected during 1987-1988.

How did NIOSH do the study?

• We estimated silica exposure for each worker by using available silica exposure information based on each worker’s job and plant.
• We collected smoking information for about 10% of the workers. We used the information to represent the smoking histories of the whole study group.
• We collected death certificates for the workers who had died.
• We compared the number of deaths from each cause among the workers, to the number of deaths expected in the U. S. general population who were of similar age, race, and sex.
• We compared the number of workers who had end-stage kidney disease with the number of people expected based on the U.S. general population. (We did not compare the number of deaths.)
• We also tested to see if the number of deaths from each cause and the number of cases of end-stage kidney disease were increased among industrial sand workers who had greater exposure to silica as compared to those who had less exposure.

What were the study results?

We found that a statistically significantly greater number of deaths occurred from the following causes among industrial sand workers compared to what was expected, based on the U.S. general population. This means that the larger number of deaths from these causes among the sand workers was very unlikely to have occurred by chance.

Lung Cancer

If the risk in industrial sand workers was the same as the risk in the general public, we would have expected 68 deaths from lung cancer. Instead we found 109. This was approximately 1½ times the number of lung cancer deaths expected. Excess risk of lung cancer has also been found in other studies of silica-exposed workers.

The greater the total amount of exposure to silica, the greater was the risk of lung cancer in industrial sand workers.

Pneumoconioses/Silicosis

Pneumoconioses are very rare causes of death due to breathing in dusts. Silicosis is one type of pneumoconiosis caused by breathing in silica dust. Silicosis causes scarring of the lungs and severe breathing problems.

Among this population, the pneumoconioses deaths were all likely due to silicosis because of the workers’ exposure to silica dust. If the risk in industrial sand workers was the same as the risk in the general public, we would have expected less than 1 death from all pneumoconioses, but we found 17.This number was more than 17 times the number expected. Excess risk of pneumoconioses has also been found in other studies of silica-exposed workers.

Tuberculosis (TB)

If the risk in industrial sand workers was the same as the risk in the general public, we would have expected 1½ deaths from TB, but found 5. This number was more than 3 times the number expected. Excess risk of TB has also been found in other studies of silica-exposed workers.

End-Stage Kidney Disease

If the risk in industrial sand workers was the same as the risk in the general public, we would have expected 12 cases (not deaths) from end-stage kidney disease, but found 23. This number was nearly 2 times the number of cases expected. Excess risk of end-stage kidney disease also has been found in other studies of silica-exposed workers.

Healthy kidneys remove waste materials from blood. End-stage kidney disease is the most serious form of kidney disease, when the kidneys no longer work. To live without kidney function, people need dialysis or a kidney transplant. Milder kidney disease can be treated to prevent end-stage kidney disease.

Arthritis

If the risk in industrial sand workers was the same as the risk in the general public, we would have expected less than 5 deaths from arthritis but found 23. This number was more than 4 times the number expected. Excess risk of arthritis has been found in some other studies of silica-exposed workers.

Heart Disease

If the risk in industrial sand workers was the same as the risk in the general public, we would have expected 270 deaths from heart disease but found 330. This number was nearly 1¼ times the number of heart disease deaths expected. Respiratory diseases such as silicosis and lifestyle factors such as smoking might account for some of the increased risk for heart disease. However, without more information on lifestyle factors within this cohort, we cannot say for certain why deaths from heart disease were increased.

Protect Yourself from Lung Disease

Smoking

• Smoking greatly increases the risk of lung cancer and lung diseases, as well as many other diseases. If you smoke, you should quit. Even if you have smoked for many years, stopping now will improve your health.
• Avoid secondhand smoke, dust, and other air pollutants, whenever possible.

Symptoms

You should see your doctor if you have the following symptoms:

1. periodic respiratory infections
2. a continuous cough
3. trouble breathing
4. feeling unusually tired

Your doctor may do a physical examination that includes a chest x-ray and a pulmonary function test (PFT).

Flu Virus

• See your doctor each year for a flu shot. The flu virus is constantly changing, so new vaccines are developed yearly to protect the public from the most recent strains of flu. For greatest protection, the best time to get the flu shot is between early October and mid-November.
• Persons 65 years of age and older should get the pneumococcal vaccine. This shot helps protect against the most common type of bacterial pneumonia. Both the flu and pneumonia shots can be given at the same time. Unlike the yearly flu shot, you need to get the pneumococcal vaccine only once in a lifetime.
• Avoid exposure to colds and flu at home and in public.

Tuberculosis

• Tuberculosis (often called TB) is an infectious disease that usually attacks the lungs. Your doctor can give you a TB skin test to find out if you have the TB infection.

Diet & Exercise

• Follow a nutritious, well-balanced diet, and maintain your ideal body weight. Eat lots of fresh fruits and vegetables. At least 5 servings a day may help to prevent cancer and other diseases.
• Get regular exercise daily, without tiring yourself too much.

Protect Yourself from Kidney Disease

You should see your doctor if you have the following symptoms:

1. Swelling of parts of the body, especially around the eyes and ankles
2. Lower back pain, where the kidneys are located
3. Burning sensation during urination
4. Bloody, foamy or coffee-colored urine
5. Changes in how often you need to urinate
6. Changes in urine color

Your doctor can decide what screening tests you may need if you have any of these symptoms.

Where To Get Additional Information

For more information call NIOSH toll-free: 800-356-4674

For more information about lung cancer and other lung diseases, call or visit these web sites:

National Cancer Institute
800-4-cancer
www.cancer.gov
American Cancer Society
800-227-2345
www.cancer.org
American Lung Association
800-586-4872
www.lungusa.org

For more information about kidney disease, contact:

American Kidney Fund
6110 Executive Boulevard
Rockville, MD 20852
800-638-8299

National Kidney Foundation
30 East 33rd Street
New York, NY 10016
800-622-9010

National Kidney and Urologic Disease Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
301-654-4415

To receive a copy of the study report or other information about occupational safety and health, contact NIOSH at:

NIOSH – Publications Department
4676 Columbia Parkway
Cincinnati, OH 45226-1998
800-356-4674
E-mail: pubstaft@cdc.gov
Web site: www.cdc.gov/niosh
Fax: 513-533-8573

Additional Resources

National Institute for Occupational Safety and Health. Website Topic Page. NIOSH Silicosis Prevention
https://www.cdc.gov/niosh/topics/silica/

Steenland K, Sanderson W (2001a). Lung cancer among industrial sand workers exposed to crystalline silica. Am J Epidemiol 153: 695-703. (Study Report)

Steenland K, Sanderson W, Calvert G (2001). Kidney disease and arthritis in a cohort study of workers exposed to silica. Epidemiology 12 (4): 405-412 (Study Report)

U.S. Department of Labor, National Institute for Occupational Safety and Health. A Guide to Working Safely With Silica. 2001-605-173/20904.
https://www.cdc.gov/niosh/pdfs/silicax.pdf (21 pages, 213kb)