Asbestosis

Description of Medical Condition

A chronic non-malignant lung disease caused by inhalation of asbestos, a hazardous dust found in a variety of work places. This disease persists in spite of substantial knowledge about its cause, and effective means of prevention. The disease typically occurs 10-15 years after initial exposure. Asbestosis is a fibrotic interstitial lung disease caused by a cascade of responses to inhaled asbestos fibers. Pleural plaques and mesotheliomas can develop. It increases risk of tuberculosis and lung cancer in cigarette smokers.

System(s) affected: Pulmonary

Genetics: No known genetic pattern

Incidence/Prevalence in USA: There is no uniform surveillance or reporting of asbestosis. In the USA, less than 10 cases per 100,000 people are diagnosed annually; this probably represents an underestimate. 876 deaths reported from 1979 to 1992. Number of cases rising steadily. More than a million people have been exposed to significant levels of asbestos. Peak use was 1940-1975.

Predominant age: Middle age (40-75 years)

Predominant sex: Male > Female, due to exposure pattern

Medical Symptoms and Signs of Disease

• No unique signs or symptoms
• Insidious onset
• Cough, dry or with sputum production
• Exercise intolerance
• Sexual dysfunction may be associated
• Basilar crackles
• Wheeze with forced exhalation
• Digital clubbing
• Cyanosis
• Right sided heart failure

What Causes Disease?

• Diversity of settings for hazardous exposure
• Asbestos used in more than 3000 commercial products — production peaked in mid-1970s
• Risk to miners and millers of asbestos
• More people at risk in construction sites with unprotected use of asbestos, commonly for insulation
• Maintenance and removal of asbestos-containing material creates high levels
• Office workers, teachers, and students in buildings with asbestos in place have exposure orders of magnitude below those of construction workers. Although societal concern has been high — actual health risk not considered significant.

Risk Factors

• Cigarette smoking markedly increases risk
• Asbestos maintenance and removal workers
• Construction workers
• Asbestos miners and millers
• Shipbuilders
• Textile workers
• Railroad workers

Diagnosis of Disease

Differential Diagnosis

Other pneumoconioses (siderosis, stannosis (due to inhalation of tin oxide), baritosis, coal worker pneumoconiosis, silicosis, talcosis, shaver’s disease)

Laboratory

• Hypoxemia
• Bronchoalveolar lavage or biopsy — generally unnecessary in the clinical setting — research tools

Drugs that may alter lab results: N/A

Disorders that may alter lab results: N/A

Pathological Findings

• Lung:
  • Parietal pleural thickening
  • Parietal pleural calcification
  • Interstitial inflammation
  • Interstitial fibrosis
  • Alveolar wall fibrosis

Special Tests

Pulmonary function test:

• Not diagnostically specific
• Useful for following level of impairment
• Restrictive, mixed, or obstructive pattern
• Reduction in diffusing capacity to carbon monoxide can occur early, even when chest x-ray is normal

Imaging

Chest x-ray

• Primary diagnostic modality and screening tool — approximately 80% sensitive
• Diagnosis based on: credible history of exposure, delay from exposure to detection, and typical radio-graphic findings
• Irregular, linear opacities — start in bases at periphery, and spread upwards
• Circumscribed pleural plaques
• Rounded atelectasis (pseudotumor)
• Pleural thickening
• Classification scheme available through International Labour Office

High resolution CT may increase sensitivity to near 100%

• Subpleural curvilinear lines

Diagnostic Procedures

Bronchos copy — research tool

Treatment (Medical Therapy)

Appropriate Health Care

Outpatient

General Measures

• No effective treatment to reverse the course
• Early detection essential
• Approach directed at elimination of progression, amelioration of symptoms, reduction of risk of associated disorders
• Withdrawal from exposure
• Workers with no symptoms, and only CXR changes may make an informed choice to continue employment, with maximum environmental and personal protection
• Pneumococcal and influenza vaccines
• Chest physiotherapy
• Nutritional advice
• Home oxygen
• Graded exercise
• Stop smoking

Surgical Measures

• Whole lung lavage to remove retained dust is being investigated
• Lung transplantation for severe advanced cases

Activity

Graded exercise

Diet

High calorie, high protein with advanced

Patient Education

Printed patient information available from: Asbestos Victims of America. P.O. Box 559, Capitola, CA 95010, (408)476-3646 or American Lung Association, 1740 Broadway, New York, NY 10019,(212)315-8700

Medications (Drugs, Medicines)

Drug(s) of Choice

• No specific pharmacologic treatment
• Oxygen
• Bronchodilators for pulmonary toilet

Contraindications: N/A

Precautions: N/A

Significant possible interactions: N/A

Alternative Drugs

• Antibiotics for respiratory infections
• Diuretics
• Treatment of congestive heart failure

Patient Monitoring

• Chest x-rays
• Occasional pulmonary function tests
• Treat infections promptly

Prevention / Avoidance

• Primary responsibility of employers
• Exposure control — substitution of safer material or adoption of control technologies
• Monitor workplace exposure
• During high exposure periods such as building repair
• use of fit-tested personal respirators for workers

WHO recommendations for regular health screening of exposed workers

• Chest x-ray at baseline
• For workers with less than 10 years since first exposure: chest x-ray every 3-5 years
• Longer than 10 years: chest x-ray every 1 -2 years
• Longer than 20 years: chest x-ray annually
• All workers: annual respiratory symptom questionnaire, physical exam, and spirometry (alternatively can be done on CXR schedule)

Reporting of new cases to health authorities

Possible Complications

• Cancers of the mesothelium of the lung
  • Unrelated to tobacco use
• Lung cancer
  • Risk increased in smokers by asbestos workers
• Gastrointestinal cancer risk may be increased
• Exudative pleural effusion
  • Resolve with residual pleural thickening
• Hyaline plaques on parietal pleura can create pseudo-tumors
• Increased risk of tuberculosis in smokers

Expected Course / Prognosis

• Severity depends on duration of exposure and on intensity of exposure
• Lung disease irreversible
• Further increased lung cancer risk with smoking
• Increased risk for mesotheliomas
• Increased risk for tuberculosis

Miscellaneous

Associated Conditions

N/A

Age-Related Factors

Pediatric: N/A

Geriatric: More likely to have terminal respiratory illness

Pregnancy

N/A

Synonyms

Asbestos pneumoconiosis

International Classification of Diseases

501 Asbestosis

See Also

Abbreviations

CT = computerized tomography

CXR = chest x-ray

WHO = World Health Organization