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Asbestosis

Pulmonary fibrosis - from asbestos exposure, Idiopathic interstitial pneumonitis - from asbestos exposure

Overview

Asbestosis is a chronic inflammatory and fibrotic medical condition affecting the parenchymal tissue of the lungs caused by the inhalation and retention of asbestos fibers. It usually occurs after high intensity and/or long-term exposure to asbestos (particularly in those individuals working on the production or end-use of products containing asbestos) and is therefore regarded as an occupational lung disease. People with extensive occupational exposure to the mining, manufacturing, handling, or removal of asbestos are at risk of developing asbestosis. Sufferers may experience severe dyspnea (shortness of breath) and are at an increased risk for certain malignancies, including lung cancer and, less commonly, mesothelioma. Asbestosis specifically refers to interstitial (parenchymal) fibrosis from asbestos, and not pleural fibrosis or plaquing.

Symptoms - Asbestosis

The signs and symptoms of asbestosis typically manifest after a significant amount of time has passed following asbestos exposure, often several decades under current conditions in the US.[3] The primary symptom of asbestosis is generally the slow onset of shortness of breath, especially with physical activity.[4] Clinically advanced cases of asbestosis may lead to respiratory failure. When a physician listens with a stethoscope to the lungs of a person with asbestosis, they may hear inspiratory rales.

The characteristic pulmonary function finding in asbestosis is a restrictive ventilatory defect. This manifests as a reduction in lung volumes, particularly the vital capacity (VC) and total lung capacity (TLC). The TLC may be reduced through alveolar wall thickening; however, this is not always the case. Large airway function, as reflected by FEV1/FVC, is generally well preserved. In severe cases, the drastic reduction in lung function due to the stiffening of the lungs and reduced TLC may induce right-sided heart failure (cor pulmonale). In addition to a restrictive defect, asbestosis may produce reduction in diffusion capacity and a low amount of oxygen in the blood of the arteries.

Causes - Asbestosis

Inhaling asbestos fibers can cause scar tissue (fibrosis) to form inside the lung. Scarred lung tissue does not expand and contract normally, and cannot perform gas exchange. The severity of the disease depends upon the duration of exposure to asbestos and the amount inhaled. Asbestos fibers were commonly used in construction before 1975. Asbestos exposure occurs in asbestos mining and milling industries, construction, fireproofing, and other industries. In families of asbestos workers, exposure can also occur from particles brought home on the worker's clothing.

Prevention - Asbestosis

Reducing exposure to asbestos is the best prevention against asbestosis. In the United States, federal law requires employers in industries that work with asbestos products - such as construction-to take special safety measures.

Many homes built before the 1970s have materials such as pipes and floor tiles that contain asbestos. Generally, there's no cause for concern as long as the asbestos is enclosed and undisturbed. It's when materials containing asbestos are damaged that there's a danger of asbestos fibers being released into the air. However, asbestosis typically occurs only after prolonged exposure to asbestos fiber.

Diagnosis - Asbestosis

According to the American Thoracic Society (ATS), the general diagnostic criteria for asbestosis are:

  • Evidence of structural pathology consistent with asbestosis, as documented by imaging or histology
  • Evidence of causation by asbestos as documented by the occupational and environmental history, markers of exposure (usually pleural plaques), recovery of asbestos bodies, or other means
  • Exclusion of alternative plausible causes for the findings

The abnormal chest x-ray and its interpretation remain the most important factors in establishing the presence of pulmonary fibrosis. The findings usually appear as small, irregular parenchymal opacities, primarily in the lung bases. Using the ILO Classification system, "s", "t", and/or "u" opacities predominate. CT or high-resolution CT (HRCT) are more sensitive than plain radiography at detecting pulmonary fibrosis (as well as any underlying pleural changes). More than 50% of people affected with asbestosis develop plaques in the parietal pleura, the space between the chest wall and lungs. Once apparent, the radiographic findings in asbestosis may slowly progress or remain static, even in the absence of further asbestos exposure. Rapid progression suggests an alternative diagnosis.

Asbestosis resembles many other diffuse interstitial lung diseases, including other pneumoconiosis. The differential diagnosis includes idiopathic pulmonary fibrosis (IPF), hypersensitivity pneumonitis, sarcoidosis, and others. The presence of pleural plaquing may provide supportive evidence of causation by asbestos. Although lung biopsy is usually not necessary, the presence of asbestos bodies in association with pulmonary fibrosis establishes the diagnosis. Conversely, interstitial pulmonary fibrosis in the absence of asbestos bodies is most likely not asbestosis. Asbestos bodies in the absence of fibrosis indicate exposure, not disease.

Prognosis - Asbestosis

The outcome depends upon the duration and extent of the exposure. Patients who develop malignant mesothelioma have a poor probable outcome, with 75% of those affected dying within 1 year.

Treatment - Asbestosis

There is no cure available for asbestosis. Oxygen therapy at home is often necessary to relieve the shortness of breath and correct underlying hypoxia. Supportive treatment of symptoms includes respiratory physiotherapy to remove secretions from the lungs by postural drainage, chest percussion, and vibration. Nebulized medications may be prescribed in order to loosen secretions or treat underlying chronic obstructive pulmonary disease. Immunization against pneumococcal pneumonia and annual influenza vaccination is administered due to increased sensitivity to the diseases. Those with asbestosis are at increased risk for certain cancers. If the person smokes, quitting the habit reduces further damage. Periodic pulmonary function tests, chest x-rays, and clinical evaluations, including cancer screening/evaluations, are given to detect additional hazards.

Resources - Asbestosis

  • NIH
Videos
by Abidemi Uruejoma
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Research Publications