asbestosis

Asbestosis
Classification and external resources
Micrograph of asbestosis showing the characteristic ferruginous bodies and marked interstitial fibrosis (or scarring). H&E stain.
ICD-10	J61.
ICD-9	501
DiseasesDB	928
MedlinePlus	000118
eMedicine	med/171 radio/52
MeSH	D001195

Asbestosis is a chronic inflammatory medical condition affecting the parenchymal tissue of the lungs. It occurs after long-term, heavy exposure to asbestos, e.g. in mining, and is therefore regarded as an occupational lung disease. Sufferers have severe dyspnea (shortness of breath) and are at an increased risk regarding several different types of lung cancer.

As clear explanations are not always stressed in non-technical literature, care should be taken to distinguish between several forms of relevant diseases. According to the World Health Organisation (WHO), these may be defined as; asbestosis (the subject of this article), lung cancer, and mesothelioma (generally a very rare form of cancer, but increasing in frequency as people exposed to asbestos age).

Signs and symptoms

Chest X-ray in asbestosis shows plaques above the diaphragm.

The primary symptom of asbestosis is generally the slow onset of shortness of breath on exertion.^[1] In severe, advanced cases, this may lead to respiratory failure. Coughing is not usually a typical symptom, unless the patient has other, concomitant respiratory tract diseases.

People with extensive occupational exposure to the mining, manufacturing, handling or removal of asbestos are at risk of developing asbestosis.^[2] There is also an increased risk of lung cancer and mesothelioma. Asbestosis and lung cancer require prolonged exposure to asbestos. However, cases of mesothelioma have been documented with even 1-3 months of exposure,^[3][4] and only indirect exposure (through air ventilation system). Most cases of asbestosis do not become apparent until 5–10 years after the initial exposure to the material.

Pathogenesis

Asbestosis is the scarring of lung tissue (around terminal bronchioles and alveolar ducts) resulting from the inhalation of asbestos fibers.^[5] There are two types of fibers: amphibole (thin and straight) and serpentine (curved). The former are primarily responsible for human disease as they are able to penetrate deeply into the lungs. When such fibers reach the alveoli (air sacs) in the lung, where oxygen is transferred into the blood, the foreign bodies (asbestos fibers) cause the activation of the lung's local immune system and provoke an inflammatory reaction. This inflammatory reaction can be described as chronic rather than acute, with a slow ongoing progression of the immune system in an attempt to eliminate the foreign fibers. Macrophages phagocytose (ingest) the fibers and stimulate fibroblasts to deposit connective tissue. Due to the asbestos fibers' natural resistance to digestion, the macrophage dies off, releasing cytokines and attracting further lung macrophages and fibrolastic cells to lay down fibrous tissue, which eventually forms a fibrous mass. The result is interstitial fibrosis. The fibrotic scar tissue causes alveolar walls to thicken, which reduces elasticity and gas diffusion, reducing oxygen transfer to the blood as well as the removal of carbon dioxide.

Asbestosis presents as a restrictive lung disease. The total lung capacity (TLC) may be reduced through alveolar wall thickening; however this is not always the case.^[6] In the more 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).^[7][8]

More than 50% of people affected with asbestosis develop plaques in the parietal pleura, in the space between the chest wall and lungs. Clinically, patients present with dry inspiratory crackles, clubbing of the fingers, and a diffuse fibrotic pattern in the lower lung lobes (where asbestosis is most prevalent).

Treatment

There is no curative treatment.^[9] Oxygen therapy at home is often necessary to relieve the shortness of breath. 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 dilute secretions.

Legal issues

The first lawsuits against asbestos manufacturers were in 1929. Since then, many lawsuits have been filed against asbestos manufacturers and employers,^[9] for neglecting to implement safety measures after the link between asbestos, asbestosis and mesothelioma became known (some reports seem to place this as early as 1898 in modern times). The liability resulting from the sheer number of lawsuits and people affected has reached billions of dollars. The amounts and method of allocating compensation have been the source of many court cases, and government attempts at resolution of existing and future cases.

See also

• Pneumoconiosis

References

External links

• ATSDR Case Studies in Environmental Medicine: Asbestos Toxicity U.S. Department of Health and Human Services
• British Government Health and Safety Executive
• Asbestos Exposure - National Cancer Institute, USA
• Public Health Guidance: Asbestos, Queensland Govt., Australia (broken link)
• Integrated Risk Information System: Asbestos
• Information on Asbestos Induced Conditions