Health Effects of 

Overexposure to 

Respirable Silica Dust

Silica Dust Control Workshop 

Elko, Nevada 

September 28, 2010 

Jay Colinet 

Office of Mine Safety and Health Research 

Senior Scientist 

National Institute for Occupational Safety 

and Health (NIOSH) 
Acknowledge Colleagues at NIOSH’s 

Division of Respiratory Disease Studies

• Anita Wolfe, Public Health Advisor 

• Edward L. Petsonk, MD, Senior Medical Officer (retired) 
Presentation Outline 

• Silica dust 

• Lung diseases in mining 

• Magnitude of impact on mining industry 

• NIOSH efforts 

• Black lung video 
Silica Dust 

• 2nd most common element in the earth’s crust (27.7%) 

• Found in many types of rock and ore 

• Respirable-sized silica particles liberated during drilling, 

crushing, loading, and dumping 

Silica particles 

embedded in 

limestone 

THIN SECTION 

200x MAGNIFICATION 
Respirable Silica Dust in Mining 

• Dust less than 10 microns in size (cannot be seen with the eye) 

• Overexposure can cause lung disease 

• X-ray surveillance may be initial means of disease diagnosis 

• Current dust exposures limits established in 1977 

• Occupational sampling conducted by MSHA to monitor exposure 

• Control technologies developed and used to reduce worker 

exposures 
Diseases Caused by Inhalation of Respirable 

Mine Dust 

• Fibrotic diseases – damage/destroy lung tissue: 

– Coal workers’ pneumoconiosis (CWP) 

– Silicosis 

• Airflow diseases (COPD) – block movement of air in and 

out of lungs: 

– Bronchitis 

– Emphysema 

– Mineral dust airway disease 
Fibrotic Lung Diseases in Miners 

Silicosis and CWP: 

– Similar patterns on chest x-ray 

– Simple and complicated forms of disease 

– Complicated is progressive massive fibrosis (PMF) 

– Smoking does not cause these diseases 

– International Labour Office (ILO) standards used to 

determine severity 

– Cannot be cured, so prevention is the key
International Labour Office Classification 

of Radiographs 

l------------------ simple pneumoconiosis -----------------------l l--- PMF ---l 

ILO 0/- 0/0 0/1 1/0 1/1 1/2 2/1 2/2 2/3 3/2 3/3 3/+ A B C 

classification
Pneumoconiosis 

• Chronic lung disease resulting from inhalation of respirable dust 

• Dust deposits in the lungs, damages lung tissue, and causes 

scarring 

• Disease development typically takes over 10 years of dust 

exposure 

• Silicosis results from inhalation of respirable silica dust 

• Coal workers’ pneumoconiosis (black lung disease) results from 

inhalation of respirable coal dust 
Simple Pneumoconiosis 

• Initially worker may not have any symptoms 

• As disease progresses, symptoms appear: 

– Coughing 

– Wheezing 

– Shortness of breath (especially during exercise) 

• Disease can advance to PMF 
Simple Silicosis 
Complicated Pneumoconiosis 

• Progressive massive fibrosis (PMF) 

• Fibrous tissue develops in lungs 

• Lungs become stiff and cannot expand fully 

• Breathing becomes difficult 

• Lips and fingernails may have bluish tinge 

• Fluid retention and signs of heart failure 
Progressive Massive

Fibrosis 
Exposure to Respirable Crystalline Silica 

• Silica more toxic than coal and is regulated to 1/20th

the level of coal dust 

• Freshly fractured silica more toxic than aged silica 

• Smaller particles are more problematic 

• Consequences of overexposure: 

– Silicosis 

– Airways diseases 

– Pulmonary tuberculosis 

– Chronic renal disease 

– Lung cancer (silica classified as a carcinogen) 
Silicosis Classifications

• Chronic: 

– Occurs after 10 or more years of exposure 

– Swelling in lungs 

– Troubled breathing similar to COPD 

• Accelerated: 

– Develops in 5 to 10 years 

– Symptoms occur faster than in chronic silicosis 

• Acute: 

– Develops in less than 5 years 

– Lungs become inflamed and fill with fluid 

– Severe shortness of breath and low blood oxygen 
Acute Silicosis at Gauley Bridge, WV 

• Hydroelectric project in early 1930s near Gauley Bridge, WV 

• Drive a 3-mile tunnel to redirect the New River through the Gauley 

Mountain 

• Sandstone and limestone strata containing high levels of silica 

• Over 450 deaths resulting from acute silicosis 
Treatment of Lung Disease in Miners 

• No medication can reverse damage from dust 

• Treatment directed at reducing symptoms and 

prevention of complications: 

– Vaccines against flu and pneumonia 

– Antibiotics for infections and congestion 

– Bronchodilators for airway spasm 

– Oxygen supplementation 

– Treatment for heart failure 

• Lung/heart transplant as last resort 
Silicosis-related Deaths 

• General consensus is that the disease is under reported 

• All states do not report statistics on industry/occupations of impacted workers 

(information available for only 1/3 of total deaths) 

• Metal/nonmetal (M/NM) mining and quarrying accounted for 15% of reported 

deaths from 1990s 

0

50

100

150

200

250

Deaths

95 96 97 98 99 00 01 02 03 04

Year
CWP More Effectively Tracked in 

Underground Coal Miners

• Surveillance and benefits program mandated by the Federal Coal 

Mine Health and Safety Act of 1969 

• Periodic x-rays available to underground coal miners (voluntary) 

• NIOSH administers program 

• Statistics more readily available 
Trends in CWP Prevalence by Tenure Among Examinees 

Employed at Underground Coal Mines 

(U.S. National Coal Workers’ X-Ray Surveillance Program, 1970–2006)

0

5

10

15

20

25

30

35

40

70-74 75-79 80-84 85-89 90-94 95-99 00-04 05-06 Prevalence (%)

Tenure (yrs): 0-9 10-14 15-19 20-24 25+

Category 1/0 + 
Need for Increased Emphasis on Dust Control 

• Overexposures continue for high-risk occupations 

• DRDS identified an increase in black lung disease, rapid 

progression of the disease, and disease in younger miners 

(Enhanced Coal Workers’ Health Surveillance Program) 

• S-MINER Bill proposed reduced dust standards: 

– 1.0 mg/m3 coal mine dust standard 

– 50 g/m3

 silica dust standard 

 

• MSHA has placed coal dust on regulatory agenda for 2010 and 

silica dust on regulatory agenda for 2011 

• As mining becomes more efficient and production increases, the 

potential to generate more dust also increases 
NIOSH Efforts: 

• Initiating research to examine control technologies that can help 

industry comply with anticipated reductions in dust standards 

• Compiled two publications that summarize dust control technologies 

for coal and metal/nonmetal mining (Best Practices Information 

Circulars 9517 & 9521) 

• Conducting workshops to assist in transferring information to 

stakeholders and gain feedback 

• DRDS produced “Faces of Black Lung” video to raise awareness of 

pneumoconiosis in miners 
“Faces of Black Lung” DVD 

• Same type of disease as 

silicosis 

• DRDS interviewed two coal 

miners that have contracted 

CWP 

• Miners discuss the importance 

of protecting themselves from 

dust exposure 

• Copies available from Anita 

Wolfe (304) 285-6263

Website for video: http://www.cdc.gov/niosh/docs/video/2008-131/default.html
Slide with Link to “Faces of Black Lung” video 

http://www.cdc.gov/niosh/docs/video/2008-131/
Important Messages...... 

“And always remember: What’s on your 

face you can wash-off, but what’s on your 

lungs you can’t. So be safe, and take care 

of yourself ”. 

Carl Bailey 

58 years old. 

Worked 28 years in 

WV mines, with 

most of his work at 

the face 

“I was always trained to avoid injuries 

and I should’ve paid more attention to 

the dust.”

 Chester Fike 

55 years old. 

Worked 34 years in mines 

in WV and MD and operated 

a continuous miner for 27 years. 
Disclaimer

The findings and conclusions in this 

presentation are those of the authors and do not 

necessarily represent the views of NIOSH. 

Mention of any company or product does not 

constitute endorsement by the National Institute 

for Occupational Safety and Health (NIOSH). In 

addition, citations to Web sites external to NIOSH 

do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or 

products. Furthermore, NIOSH is not responsible 

for the content of these Web sites. All Web 

addresses referenced in this presentation were 

accessible as of the date the presentation was 

originally delivered.
Thank you! 

Questions?? 

Jay Colinet 

Office of Mine Safety and Health Research 

NIOSH 

P.O. Box 18070 

Pittsburgh, PA 15236 

412-386-6825 

jcolinet@cdc.gov