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 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 and are at an increased risk for certain malignancies,
including lung cancer but especially mesothelioma.
Asbestosis specifically refers to interstitial fibrosis from asbestos, and not pleural fibrosis
or plaquing.
Signs and symptoms
The signs and symptoms of asbestosis do not manifest until after an appreciable latency,
often several decades under current conditions in the US.
The primary symptom of asbestosis is generally the slow onset of dyspnea, especially on exertion.
Clinically advanced cases of asbestosis may lead to respiratory failure.
On auscultation of the lungs, the physician 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 and total
lung capacity.
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 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.
In addition to a restrictive defect, asbestosis may produce reduction in diffusion capacity
and arterial hypoxemia.
Pathogenesis Asbestosis is the scarring of lung tissue
resulting from the inhalation of asbestos fibers.
There are two types of fibers: amphibole and serpentine.
The former are primarily responsible for human disease as they are able to penetrate deeply
into the lungs.
When such fibers reach the alveoli in the lung, where oxygen is transferred into the
blood, the foreign bodies 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 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.
This mass can be seen microscopically, with the asbestos fiber layered by an iron-containing
proteinaceous material.
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.
Diagnosis
According to the American Thoracic Society, 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, 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 are more sensitive than plain radiography at detecting pulmonary
fibrosis.
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 pneumoconioses.
The differential diagnosis includes Idiopathic Pulmonary Fibrosis, 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.
Treatment There is no curative treatment 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.
Patients are at increased risk for certain malignancies.
If the patient smokes, cessation reduces further damage.
Periodic PFTs, chest x-rays, and clinical evaluations, including cancer screening/evaluations,
are given to detect additional hazards.
Legal issues
The death of English textile worker Nellie Kershaw in 1924 from pulmonary asbestosis
was the first case to be described in medical literature, and the first published account
of disease attributed to occupational asbestos exposure.
However, her former employers denied that asbestosis even existed because the medical
condition was not officially recognised at the time.
As a result, they accepted no liability for her injuries and paid no compensation, either
to Kershaw during her final illness or to her bereaved family after she had died.
Even so, the findings of the inquest into her death were highly influential insofar
as they led to a parliamentary enquiry by the British Government.
The enquiry formally acknowledged the existence of asbestosis, recognised that it was hazardous
to health and concluded that it was irrefutably linked to the prolonged inhalation of asbestos
dust.
Having established the existence of asbestosis on a medical and judicial basis, the report
resulted in the first Asbestos Industry Regulations being published in 1931, which came into effect
on 1 March 1932.
The first lawsuits against asbestos manufacturers occurred in 1929.
Since then, many lawsuits have been filed against asbestos manufacturers and employers,
for neglecting to implement safety measures after the link between asbestos, asbestosis
and mesothelioma became known.
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.
Notable cases Some notable persons who have died from lung
fibrosis associated with asbestos include: Bernie Banton, social justice advocate
Nellie Kershaw, first person diagnosed with asbestos-related disease, 1924
John MacDougall, politician Steve McQueen, actor
Theodore Sturgeon, writer Dr.Raymond Sentes social justice advocate,Professor
of Political Science Additional images
See also Pneumoconiosis
Chandler v Cape plc [2011] EWHC 951 the first successful case in England by an asbestosis
sufferer against the parent company of a subsidiary that manufactured asbestos.
References
External links "Asbestos Toxicity".
ATSDR Case Studies in Environmental Medicine.
U.S. Department of Health and Human Services.
"Asbestos health and safety".
British Government Health and Safety Executive.
"Asbestos Exposure".
National Cancer Institute, USA.
"Environmental Health Guidance Note — Asbestos".
Queensland Health.
May 2002.
"Asbestos".
IRIS — Integrated Risk Information System.
US Environmental Protection Agency.
CASRN 1332-21-4.
"Asbestosis".
Canadian Lung Association.
"Microphotograph of asbestos fibers in the lung".
ASTDR.