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Asbestos Toxicity
Clinical Assessment

Course: WB 2344
CE Original Date: January 29, 2014
CE Expiration Date: January 29, 2016
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Learning Objectives

Upon completion of this section, you will be able to

  • Identify the primary focuses of the patient exposure history (exposure and medical) and
  • Describe the most typical finding on examination of asbestosis patients.

Introduction

Patients who have been significantly exposed to asbestos should undergo a thorough medical evaluation. Early and accurate diagnosis is important to your choosing the most appropriate care strategies, even if the patient is not exhibiting symptoms. In cases of asbestos exposure, medical evaluation should include

  • An assessment of clinical presentation,
  • An exposure history (See ATSDR Case Study in Environmental Medicine: Taking an Exposure History),
  • A medical history,
  • A physical examination, and
  • A chest radiograph or other imaging and pulmonary function tests [American Thoracic Society 2004].

This section focuses on the first four items, which are typically conducted during the patient's visit to your office. Recommended tests are discussed in the next section.

Clinical Presentation

Many people with occupational exposure to asbestos never have serious asbestos-related diseases. However, asbestos-associated diseases typically have long latency periods so many patients exposed to asbestos are asymptomatic for years before any clinically apparent asbestos-related disease develops. If and when asbestos-associated disease does manifest clinically, the patient's symptoms depend on the type and stage of disease(s) involved (see table). A single patient can have any combination of asbestos-associated diseases.

Table 11. Clinical Presentation of Asbestos Associated Diseases

Asbestos-Associated Disease Clinical Presentation
Asbestosis

Presenting Symptoms

  • Dyspnea on exertion
  • Nonproductive cough
  • Fatigue
  • Signs
  • Wheezing
  • Bibasilar end-inspiratory rales (i.e., crackles) on ausculation of the chest

Advanced Stages.

  • Clubbing of the fingers
  • Dyspnea at rest
  • Cyanosis
  • Cor pulmonale (rare)

Asbestos-related non-malignant pleural abnormalities

Presenting Symptoms

  • Usually none
  • In some cases, intermittent chest pain, rarely can be severe.

Lung cancer

Presenting Symptoms

  • Early in the course, usually none. Sometimes none, if cancer is found incidentally (e.g., on a chest radiograph done for another reason).
  • Occasionally, dry cough

Advanced Stages

  • Hemoptysis
  • Chest pain, usually severe
  • Weight loss
  • Fatigue
  • Dyspnea (due to pleural effusion or obstructive pneumonia)

Mesothelioma

Presenting Symptoms

  • Frequently presents with chest pain and dyspnea

Advanced Stages

  • Dyspnea (due to space-occupying mass and/or pleural effusion)
  • Severe and progressive chest pain, sometimes pleuritic in nature
  • Systemic signs of cancer such as weight loss and fatigue

Source: British Thoracic Society 2001; American Thoracic Society 2004

Exposure History

Taking a detailed exposure history is an important step in evaluating a patient who may be at risk for developing asbestos-associated diseases. In general, risk of asbestos-related disease increases with total dose [Khan et al. 2013]. However, since asbestos accumulates in the body, even relatively minor exposures many years in the past could be important in diseases like mesothelioma. The exposure history should include

  • Work history, including occupations in which the patient may have been exposed directly or indirectly.
  • Source, intensity, frequency and duration of exposure.
  • Time elapsed since first exposure.
  • If extant, workplace dust measurements or cumulative fiber dose (or exposure scenario, if levels cannot be determined).
  • Use of personal protective equipment.
  • Other sources of exposure, including paraoccupational exposures from family members and other household contacts.
  • Sources of environmental exposure, including residence near an area with naturally occurring asbestos deposits or hobbies or recreational activities that involve materials that contain asbestos).
  • Smoking history and sources of other environmental contaminants such as environmental tobacco smoke [American Thoracic Society 2004].

For more information on the exposure history, see the Taking an Exposure History CSEM at http://www.atsdr.cdc.gov/csem/csem.asp?csem=17&po=0

See the table below for typical exposures for each of the asbestos-associated diseases.

Table 12. Estimated Exposures and Disease Risk for Asbestos

Asbestos-Related Disease Typical Exposure History
Asbestosis Usually associated with high-level occupational exposures, not with paraoccupational or environmental exposures [Khan et al. 2013].
Asbestos-related non-malignant pleural abnormalities

Presence of pleural plaques depends more on time from first exposure rather than on a threshold dose [Larson et al. 2010b], but the incidence of this disorder in a population does increase with exposure. Occurs in 0.5% to 8% of environmentally exposed individuals and up to 58% of insulation workers [Peacock et al. 2000].

Non-malignant pleural effusion earliest manifestation of asbestos exposure. They can occur within ten years of asbestos exposure.

Diffuse pleural thickening is associated with more extensive asbestos exposure than pleural plaques.

Folded atelectasis not only occurs after asbestos exposure but is associated with other exposures and medical conditions.

Lung cancer Dose-related. Synergistic relationship with smoking [Jaklitsch et al. 2012].
Mesothelioma Not as clearly dose-related as other asbestos-related diseases, but the risk does appear to increase with dose. Can be found in residents near asbestos mines and with paraoccupational exposure. [British Thoracic Society 2001].

Medical History

Knowing the complete medical history of a patient who has been exposed to asbestos is important to making an accurate diagnosis. It is especially important to ask about a history of smoking and exposure to environmental tobacco smoke, because exposure to tobacco smoke, especially active smoking, can greatly increase risk of lung cancer and can worsen the effects of asbestosis in asbestos-exposed patients.

Particularly for asbestos-related non-malignant diseases, it is important to be aware of other respiratory and non-respiratory conditions that may have similar clinical presentations in order to rule them out.

Physical Examination

Patients with a history of asbestos exposure should receive a full physical examination with special attention to the respiratory system. In the case of early or mild disease, there will probably be no abnormal physical findings. The most common abnormal finding with significant asbestosis is bibasilar end-inspiratory rales (i.e., crackles) on auscultation. These are described as sounding like Velcro [Ross 2003].

Physical examination should also include

  • Examination for clubbing of the fingers and cyanosis [American Thoracic Society 2004],
  • Examination of the extremities for symmetrical dependent edema, one of the physical findings of cor pulmonale,
  • Abdominal palpitation for abnormal masses or signs of peritoneal effusion that can accompany peritoneal mesothelioma, and
  • Fecal occult blood testing to screen for colorectal cancer screening [CDC 2013].

Differential Diagnosis

Several other non-asbestos related respiratory and non-respiratory conditions have symptoms similar to those of asbestos-associated diseases. It is important to distinguish these conditions, for some of which have specific treatments different from asbestos-related non-malignant diseases, for which medical treatment is entirely symptomatic (see table).

It is also important to distinguish non-malignant asbestos-associated conditions from malignant conditions such as lung cancer and mesothelioma. In cases that are not clear cut, a referral to a pulmonary specialist for further workup is indicated.

Table 13. Differential Diagnosis of Respiratory Conditions that Can Be Confused with Asbestos-related Conditions

Asbestos-Related Condition Differential Diagnosis: Respiratory Condition Differential Diagnosis: Non-Respiratory Condition
Asbestosis

  • Rheumatoid arthritis and other connective tissue diseases (with pleural or pulmonary involvement)
  • Other pneumoconiosis:
    • Talc
    • Titanium
    • Zeolite
  • Interstitial pulmonary fibrosis (IPF), including idiopathic pulmonary fibrosis
  • Hypersensitivity pneumonitis
  • Sarcoidosis
  • Drug-related fibrosis
  • Other pulmonary fibrosis

  • Left ventricular failure (presents with dyspnea, rales, edema, restriction, and basilar markings on chest film)

Asbestos-related non-malignant pleural disease

Single pleural plaques

  • Malignant mesotheliomas and metastatic adenocarcinomas [Khan et al. 2013]

Single calcified pleural plaques

  • Empyema
  • Hemothorax
  • Tuberculosis [Khan et al. 2013]

Bilateral calcified pleural plaques

  • Most commonly asbestos-related but in rare cases
    • Radiation exposure
    • Hyperparathyroidism
    • Pancreatitis [Khan et al. 2013]
  • Diffuse pleural thickening

    • Post-exudative effusions such as parapneumonic effusions and those secondary to connective tissue disease
    • Hemothorax
    • Mesothelioma [Khan et al. 2013]

    Rounded atelectasis (folded lung)

    • Lesions that are similar in appearance to rounded atelectasis (i.e., solitary pulmonary mass) are
      • Malignancies such as bronchogenic carcinoma, metastasis, lymphoma
      • Benign neoplasms such as hamartoma and adenoma
      • Vascular causes such as arteriovenous malformation, pulmonary infarct, hematoma
      • Infections such as tuberculosis, round pneumonia, fungal infections [Khan et al. 2013]

    Prior thoracic surgery/chest wall configuration
    Lung carcinoma

    Other causes of a solitary pulmonary nodule

    • Folded lung
    • Metastatic lesion
    • Lymphoma
    • Benign neoplasms such as hamartoma or adenoma
    • Vascular lesion such as a arteriovenous malformation, pulmonary infarction or hematoma
    • Infectious lesions from tuberculosis, fungal infections [Khan et al. 2013]

    Malignant mesotheli-oma

    • Diffuse pleural thickening
    • Metastatic adenocarcinoma [Khan et al. 2012; British Thoracic Society 2001]

    Key Points

    • The exposure history focuses on finding information on exposures to asbestos.
    • The medical history focuses on smoking history and other respiratory conditions.
    • The most typical abnormal finding on examination of patients with a history of asbestos exposure is bibasilar end-inspiratory rales on auscultation.
    • Patients with asbestosis present to the clinician with the chief complaint of insidious onset of dyspnea on exertion.
    • Asbestos-related non-malignant pleural abnormalities typically do not cause symptoms, although some patients experience progressive dyspnea and chest pain.
    • Lung cancer can be asymptomatic, but in the later stages patients experience fatigue, weight loss, chest pain, dyspnea, or hemoptysis.
    • Mesothelioma can be asymptomatic, but patients usually present in later stages of the disease, at which point dyspnea and chest pain are common.

       

    Progress Check

    16. The most typical abnormal finding on physical examination of a patient with significant asbestosis is

    A. Cyanosis.
    B. Bibasilar inspiratory rales on auscultation.
    C. Clubbing of the fingers.
    D. All of the above.

    Answer:

    To review relevant content, see "Physical Examination" in this section.

    17. Why is it important to know a patient's exposure history?

    A. Asbestos-associated diseases have symptoms similar to those of treatable diseases, and the exposure history assists a differential diagnosis.
    B. Activities such as smoking can increase a patient's risk of asbestos-related diseases.
    C. Asbestos accumulates in the body and, for certain disorders, even minor exposures can be important.
    D. All of the above.

    Answer:

    To review relevant content, see "Exposure History" in this section.

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