Asbestosis – Causes, Symptoms, Diagnosis, Treatment

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Asbestosis is an interstitial lung disease caused by the inhalation of asbestos fibers. These fibers are different mineral silicates (mainly hydrated magnesium silicates) and are classified into two main categories based on their shape i.e., serpentine and amphibole. Serpentine fibers include chrysolites that are curly and flexible and are less pathogenic than amphibole fibers. Chrysolite being more flexible, curvy, and more soluble settles in the upper part of the respiratory tract. The mucociliary function is more prominent in the upper respiratory tract, so chrysolite fibers are easily removed. Amphiboles (crocidolite, amosite, tremolite, and anthophyllite) are straight, stiff, more brittle fibers.

Asbestosis is a lung disease that develops when asbestos fibers cause scarring in your lungs. The scarring restricts your breathing and interferes with the ability of oxygen to enter your bloodstream. Other names for this disease are pulmonary fibrosis and interstitial pneumonitis.

Types of Asbestos Fibers

Asbestos is a naturally occurring silicate mineral. It is found worldwide and close to the earth’s surface making it easy and economical to mine. Asbestos has two distinct groups based on its fiber composition. One is the serpentine class. The other is amphibole asbestos fibers that contain five different subtypes.

Chrysotile fibers are the only type of serpentine asbestos.

When microscopically viewed, chrysotile or white asbestos fibers appear:

  • Long
  • Soft
  • Wavy
  • Serpent shaped

Approximately 90 percent of all asbestos used in American materials were chrysotile fibers. Therefore, due to their abundance, chrysotile asbestos was responsible for the vast majority of asbestosis cases.

The shape and softness of the chrysotile type also account for why most asbestos-caused diseases are benign. They didn’t do as much damage as amphibole fibers.

Amphibole class fibers look hard and spiky under a microscope. Each fiber particle contains needle-like spears that cut into lung tissue and traveled to the outer lining which is called the mesothelium. Some amphibole-class fibers remained in the tissue and contributed to scar tissue build-up resulting in asbestosis.

Amphibole asbestos contains five different subtypes which are:

  • Crocidolite
  • Amosite
  • Translate
  • Actinolite
  • Anthophyllite

Crocidolite asbestos is considered the most dangerous asbestos type, but the U.S. government considers all types of asbestos dangerous.

The pathology definition remains unclear. The College of American Pathologists has defined four grades of severity

  • Grade 1—fibrosis that involves the wall of a respiratory bronchiole
  • Grade 2—Grade 1 plus involvement of alveolar ducts and adjacent alveoli, but with some nonfibrotic adjacent alveolar septae
  • Grade 3—Grade 2 fibrosis, but with coalescence, such that all alveoli between two adjacent bronchi show fibrotic septa, with some complete obliteration
  • grade 4—Grade 3 fibrosis plus honeycombing

A supplementary scoring system has been developed to describe the degree of airway involvement.

Alternative Names

Pulmonary fibrosis – from asbestos exposure; Interstitial pneumonitis – from asbestos exposure

Causes of Asbestosis

Breathing in asbestos fibers can cause scar tissue (fibrosis) to form inside the lung. Scarred lung tissue does not expand and contract normally.

How severe the disease depends on how long the person was exposed to asbestos and the amount that was breathed in and the type of fibers breathed in. Often, the symptoms aren’t noticed for 20 years or more after the asbestos exposure.

Asbestos fibers were commonly used in construction before 1975. Asbestos exposure occurred in asbestos mining and milling, construction, fireproofing, and other industries. Families of asbestos workers can also be exposed from particles brought home on the worker’s clothing.

Other asbestos-related diseases include:

  • Pleural plaques (calcification)
  • Malignant mesothelioma (cancer of the pleura, the lining of the lung), which can develop 20 to 40 years after exposure
  • Pleural effusion, which is a collection that develops around the lung a few years after asbestos exposure and is benign
  • Lung cancer

Workers today are less likely to get asbestos-related diseases because of government regulations.

Cigarette smoking increases the risk of developing asbestos-related diseases.

Many workers are at risk of exposure to asbestos, particularly shipbuilders, textile and construction workers, home remodelers, workers who do asbestos abatement, and miners who are exposed to asbestos fibers. Secondhand exposure may occur among family members of exposed workers and among people who live close to mines.

Specific occupations at highest risk of exposure include welders, auto mechanics, tile setters, boilermakers, U.S. Navy personnel, shipyard workers, merchant marines, sheet metal workers, bricklayers, building inspectors, carpenters, roofers, plumbers, plasterers, refinery workers, pipefitters, painters, demolition workers, drywall workers, electricians, floor covering workers, furnace workers, glaziers, millwrights, insulators, ironworkers, laborers, Libby vermiculite exfoliation plant workers, longshoremen, maintenance workers.

Symptoms of Asbestosis

The following are symptoms of asbestosis:

  • Shortness of breath, which may begin with exercise
  • A long-term dry cough
  • Coughing up blood
  • Chest tightness
  • Chest pain
  • Loss of appetite with weight loss
  • A dry, crackling sound in the lungs while breathing in
  • Fingertips and toes that are wider and rounder than normal (called clubbing)

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.[rx] The primary symptom of asbestosis is generally the slow onset of shortness of breath, especially with physical activity.[rx] 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 crackles.

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Advanced Symptoms

  • Pulmonary Hypertension – The formation of scar tissue may also constrict arteries and make it harder to pump blood out of the heart and into the lungs without increasing the pressure required to perform the action. This is called pulmonary hypertension, which is a different condition from the more commonly occurring “high blood pressure” or systemic hypertension. Pulmonary hypertension is dangerous because it forces the heart to work harder, potentially leading to earlier problems with coronary artery disease and congestive heart failure.
  • Clubbed Fingers and Toes – When the lungs deliver insufficient oxygen to the blood, a symptom called “clubbing” may arise. The tips of the toes and fingers appear wider and rounder than normal. Fingernails and toenails may become deformed because of the lack of oxygen reaching the body’s extremities

Contact your health care provider if you have these symptoms.

Diagnosis of Asbestosis

The diagnosis of asbestosis is largely clinical. First, the history of asbestos exposure is central to the diagnosis. The overall clinical picture is characterized by progressive restrictive pulmonary disease with interstitial fibrosis on radiography. The pulmonary function test reveals characteristic restrictive disease.

These tests show images of your lungs:

  • Chest X-ray – Advanced asbestosis appears as excessive whiteness in your lung tissue. If the asbestosis is severe, the tissue in both lungs might be affected, giving them a honeycomb appearance.
  • Computerized tomography (CT) scan – CT scans combine a series of X-ray views taken from many different angles to produce cross-sectional images of the bones and soft tissues inside your body. These scans generally provide greater detail and might help detect asbestosis in its early stages, even before it shows up on a chest X-ray.

Pulmonary function tests

These tests determine how well your lungs are functioning. Pulmonary function tests measure how much air your lungs can hold and the airflow in and out of your lungs.

During the test, you might be asked to blow as hard as you can into an air-measurement device called a spirometer. More complete pulmonary function tests can measure the amount of oxygen being transferred to your bloodstream.

Diagnostic procedures

In some situations, your doctor might remove fluid and tissue for testing to identify asbestos fibers or abnormal cells. Tests may include:

  • Bronchoscopy. A thin tube (bronchoscope) is passed through your nose or mouth, down your throat and into your lungs. A light and a small camera on the bronchoscope allow the doctor to look inside your lungs’ airways for any abnormalities or to get a fluid or tissue sample (biopsy) if needed.
  • Thoracentesis. In this procedure, your doctor injects a local anesthetic and then inserts a needle through your chest wall between your ribs and lungs to remove excess fluid for lab analysis and to help you breathe better. Your doctor might insert the needle with the help of ultrasound guidance.

Pulmonary Function Tests

Spirometry and Lung Volumes

  • This includes forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), total lung capacity (TLC), functional residual capacity, and residual volume. Like any other restrictive lung disease, all earlier mentioned lung volumes are reduced.FEV1/FVC ratio is either normal or increased.

Diffusing Capacity

  • Total carbon monoxide diffusion capacity (DLCO) reduction is a common but nonspecific finding. Reduced total carbon monoxide diffusion capacity (DLCO) is manifested earlier. This is due to the mismatching of ventilation and perfusion (V/Q).

Arterial Blood Gas

  • Arterial oxygen tension (pao2) may be normal or may reveal hypoxia and respiratory alkalosis. Carbon dioxide retention is rare; if present indicates the end-stage disease, and there may also be evidence of airflow obstruction due to small airway dysfunction.
  • Nevertheless, it is important to note that asbestosis is a diagnosis of exclusion, and it is clinically relevant to differentiate asbestosis from idiopathic pulmonary fibrosis because both essentially have many similar presenting symptoms. Both asbestosis and IPF are characterized by progressive interstitial pulmonary fibrosis, with a restrictive lung disease picture in PFT.
  • There are orally subtle differences between the two radiographically and histologically. It is important to differentiate between the two because there are distinctly targeted therapies available, although not that effective.

Plain X-ray of the Chest

  • It shows interstitial fibrosis. High-resolution computed tomography (HRCT) is often diagnostic of asbestosis. HRCT shows ground-glass opacities, along with diffuse interstitial fibrosis in asbestosis whereas, in idiopathic pulmonary fibrosis, there is evidence of patches of opacities.
  • Pleural thickening and calcified pleural plaques in tomography is the hallmark of the disease. Asbestosis mimics idiopathic pulmonary fibrosis radiographically, especially in CT. An important distinguishing point is that asbestosis begins more centrally and dissipates peripherally following a centrifugal pattern.
  • In contrast, idiopathic pulmonary fibrosis begins peripherally, especially at the bases, and progresses centrally and upwards as the disease progresses. At least theoretically, IPF follows a centripetal pattern. Differentiating asbestosis and idiopathic pulmonary fibrosis (IPF) on CT can be challenging, and histopathology can be conclusive.
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Lung Biopsy

  • It shows interstitial fibrosis with characteristically peribronchial fibrosis. The distribution of fibrosis in asbestos disease is from the center to periphery, i.e., centrifugally. The microscopic view of asbestosis shows distinct Asbestos bodies coated with iron-containing proteinaceous material and diffuse pulmonary interstitial fibrosis, but in contrast, idiopathic pulmonary fibrosis (IPF) displays patchy interstitial fibrosis. The profuse proliferation of fibroblasts, i.e., fibroblastic foci and subsistence of both early and late proliferative lesions (temporal heterogeneity), are well defined in IPF and rare or absent in asbestosis.
  • A lung biopsy can be achieved by endobronchial, transbronchial, and video-assisted thoracoscopic (VAT) approaches. The endobronchial biopsy is done with ultrasound-guided bronchoscopy to visualize the airway and adjacent structures. This technique has been routinely used in many centers due to its high diagnostic value and low risk. Endoscopically-guided forceps do Transbronchial lung biopsy. Conventional transbronchial biopsy has a higher risk of complications and bleeding. The modern technique is the minimally invasive video-assisted thoracoscopic (VAT) guided biopsy. VAT has fewer complications, is more sensitive, specific, and has more diagnostic yield than transbronchial biopsy. So, VAT is preferred over transbronchial lung biopsy, though VAT has some discrepancies like cost and expertise requirement.
  • Bronchoalveolar lavage has a limited role. Samples can be taken from suspected patients for cellular analysis of asbestos bodies count, inflammatory cells like macrophages, neutrophils, eosinophils, and dust particles. Asbestos body formation is more common in amphibole fibers, while chrysotile fibers have a shorter half-life and have fewer chances of asbestos body formation. So the absence of asbestos bodies in chrysotile asbestosis leads to a false-negative result.

Lab analysis shows elevated C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, and antinuclear antibodies.

Asbestos fibres in environmental ambient air
Occurrence in air
Rural areas (remote from asbestos emission sources): below 100 F/m3
Urban areas: general levels may vary from below 100 to 1,000 F/m3
Near various emission sources the following figures have been measured as yearly averages:
   (I) Downwind from an asbestos-cement plant at 300 m: 2,200 F/m3; at 700m: 800 F/m3; at 1,000 m: 600 F/m3
   (II) At a street crossing with heavy traffic, 900 F/m3
   (III) On an express-way, up to 3,300 F/m3
Indoor air:
   (I) In buildings without specific asbestos sources, concentrations are generally below 1,000 F/m3
   (II) In buildings with friable asbestos, concentrations vary irregularly; usually less than 1,000 F*/m3 are found, but in some cases, exposure reaches 10,000 F*/m3

Treatment of Asbestosis

Asbestosis has no specific treatment, so supportive care is the only available option. Therefore, prevention is the best management. Monitoring the occupational environment and minimizing asbestos exposure has a significant role in asbestosis control.

  • Supplemental Oxygen – Supplemental oxygen from a portable oxygen tank is often necessary for patients with reduced lung capacity. The tank delivers extra oxygen to the lungs through a plastic tube with two prongs that fit into the patient’s nostrils.
  • Medications – Medications can thin lung secretions to make coughing easier and relieve chest pain. However, corticosteroids (anti-inflammatory medications) and immunosuppressants are ineffective for treating asbestosis.
  • Pulmonary Rehabilitation – Pulmonary rehabilitation helps patients learn techniques and make lifestyle changes to better cope with chronic breathing difficulties. A team of therapists works together to provide for both physical and psychological needs.
  • Lung Transplants – Lung transplants are most often considered when asbestosis is accompanied by more severe lung diseases such as emphysema or lung cancer. It is a highly invasive, last-resort treatment, and in order to be put on a lung transplant waiting list, a patient has to undergo extensive screening to determine the relative chances of success.

Drug Therapy

The goal of corticosteroid therapy is to suppress the acute and chronic inflammatory process, thereby further reducing lung damage, but the success rate is low. Steroids suppress the release of reactive species and mediators in the ongoing inflammatory process. Because of the lack of placebo-controlled trials, there is no direct evidence of the benefits of steroids in improving the survival of life. The proper dose and length of therapy of steroids are not known. High-dose corticosteroid and other immunosuppressive drugs such as azathioprine have some roles in reducing exacerbation of acute asbestosis. The starting dose of prednisolone is usually considered 0.5 to 1 mg per kg in a once-daily oral dose for 4 to 12 weeks. The patient is monitored and reevaluated. The dose is tapered to 0.25 to 0.5 mg/kg for a further 4 to 12 weeks if the patient is stable and improving. But some studies show that the use of agents like cyclophosphamide accelerates the fibrotic process, so its use is limited. If the condition is not improving and the patient is unstable, then either other drugs are added, or steroid is withdrawn. Colchicine is found to be a mild antifibrotic agent. Antibiotics therapy should be prompt for superimposed respiratory infections as well as immunization against pneumococcus and Haemophilus influenza.

Oxygenation

Patients with hypoxemia (Pao2< 55 mmHg) at rest or with exertion should be supplemented with oxygen. Pulmonary rehabilitation and management of cor pulmonale have shown to improve the quality of life as the disease progresses.

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Surgery

Decortication of subpleural fibrosis by thoracotomy improves atelectasis. Pleurectomy can be performed in pleural fibrosis. But if the collection of pleural fluid is rapid, then only palliative removal of fluids to relieve breathlessness should be done.

Lung Transplantation

This is the ultimate treatment in severe asbestosis, where all other therapies have failed in case of chronic and irreversible fibrosis.

No treatment can reverse the damage done by asbestos. You can take steps to help slow the progression, however. Most important is to prevent further exposure to asbestos and to quit smoking. There are also treatments that your provider can prescribe to help ease your breathing and maintain your lung health.

The following actions can help you manage asbestosis:

  • Prevent more exposure to asbestos.
  • If you’re a smoker, medications may help you quit. You can also take medication to ease symptoms of cigarette-related lung problems.
  • Flu and pneumonia vaccines do not treat asbestosis, but they are recommended for most people with lung disease.
  • Treat lung infections early.
  • If your oxygen levels are low, oxygen therapy may be helpful.
  • Take part in lung rehabilitation, which is an exercise program designed to help all patients with chronic lung conditions.

In severe situations, you provider may also refer you to a lung transplant specialist.

You may get sick more often when you have asbestosis. As your disease progresses, you may need to make lifestyle changes. Such changes can include oxygen therapy, attending lung rehabilitation, and learning to do daily activities in a way that keeps you from feeling too short of breath.

If you have advanced disease, you may need to be hospitalized to help with your breathing. As with all lung diseases, it is important to ask your provider how to stay as healthy as possible for as long as possible. If your provider thinks that your asbestosis will cause you to be hospitalized, he or she may recommend making plans for the future, such as filling out an advance directive. Taking these steps can ensure all of your wishes are respected.

Managing in 2nd step

Your health care team can help manage your symptoms. Follow these guidelines to prevent complications and improve your quality of life:

  • Stay healthy:
    • Eat a well-balanced diet, including lots of fruits and vegetables.
    • Drink at least 6 glasses of water daily.
    • Limit your salt intake.
  • Get enough rest:
    • Get enough sleep every night.
    • Take short rests throughout the day.
  • Exercise regularly:
    • Stay as active as you can.
    • Go to the gym, if your body allows.
    • Don’t let yourself get too tired.
    • Make sure the weather is suitable when you exercise outdoors.
  • Prevent infections:
    • Wash your hands often.
    • Avoid large crowds.
    • Get flu and pneumonia shots according to your provider’s recommendations.
  • Recognize and treat any lung infections.
  • Avoid exposure to polluted air:
    • Stay inside when air pollution is severe and pollen counts are high.
    • Avoid breathing pollutants that can trigger shortness of breath, such as secondhand smoke; traffic fumes; smog; aerosol sprays; and vapors from products such as paint, kerosene, and cleaning agents.
    • Cover your mouth and nose with a scarf to avoid breathing in cold air in cold weather.
  • Avoid further exposure to asbestos.

Pay attention to people who live with you and see if they have similar symptoms. They may have been exposed to asbestos fibers from your clothes, shoes, and body. They may be at risk for developing the disease.

Questions to ask your health care provider

Making notes before your visit and taking along a trusted family member or friend can help you through the first appointment with your provider.

You and your loved ones are likely to have many concerns and questions. These reactions are natural. It can be hard for you to know what to ask your health care team. Here are some questions that may help you:

  • How and why did I get asbestosis?
  • How advanced is my disease?
  • What is the best treatment for my condition?
  • What will my symptoms be?
  • What symptoms should alert me to go to see a health care provider?
  • What medications will I be given?
  • What other treatments besides drugs are helpful?
  • How will my disease progress?
  • How much experience do you have managing asbestosis?
  • Should I get a second opinion? Can you recommend someone?
  • Am I a candidate for a lung transplant?
  • What is the difference between asbestosis, pleural plaques, and mesothelioma?
  • Can asbestos cause other lung problems besides fibrosis and cancer?
  • My office has asbestos insulation. Will it cause lung problems?

References

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