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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.

Asbestosis

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

Asbestosis

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

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