Agency for Toxic Substances and Disease Registry
Case Studies in Environmental Medicine (CSEM) 

Asbestos Toxicity
How Should Patients Exposed to Asbestos Be Evaluated?

Learning Objectives

Upon completion of this section, you should be able to

• identify the primary focuses of the exposure history and medical history
• describe the most typical finding on patient examination

Introduction

Patients who have been 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
• a chest radiograph and pulmonary function tests

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 asbestos-related any 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.

Parenchymal asbestosis

Presenting Symptoms

• Insidious onset of dyspnea on exertion
• Fatigue.

Advanced Stages

• Clubbing of the fingers.
• Cor pulmonale (rare).

Asbestos-related pleural abnormalities

Presenting Symptoms

• Usually none.

Diffuse Pleural Thickening

• Progressive dyspnea
• Intermittent chest pain

Rounded Atelectasis

• Dyspnea
• Dry cough

Lung cancer

Presenting Symptoms

• Early in the course, usually none
• Occasionally, dry cough

Advanced Stages

• Hemoptysis
• Chest pain
• Weight loss
• Fatigue
• Dyspnea with pleural effusion

Mesothelioma

Presenting Symptoms

• Early in the course, can be asymptomatic
• Frequently presents with chest pain and dyspnea

Advanced Stages

• Dyspnea
• Severe and progressive chest pain
• Pleuritic chest pain
• 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. 2004). However, since asbestos accumulates in the body, even relatively minor exposures many years before could be important in diseases like mesothelioma. The exposure history should include the following information

• 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 a residence near an area with naturally occurring asbestos deposits or hobbies or recreational activities that involve materials that are contaminated with asbestos)
• sources of other environmental contaminants such as environmental tobacco smoke

For more information on the exposure history, see the Taking an Exposure History CSEM at

http://www.atsdr.cdc.gov/csem/exphistory/.

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

Parenchymal asbestosis

Usually associated with high-level occupational exposures, not with paraoccupational or environmental exposures (Khan et al. 2004).

Asbestos-related pleural abnormalities

Pleural Plaques

Presence depends on time from exposure, not a threshold dose. The incidence of this disorder in a population does increase with exposure. Occurs in 0.5% to 8% of environmentally exposed individuals to a high of 58% in insulation workers (Peacock et al. 2000).

Lung cancer

Large cumulative exposure. It is believed to be dose-related.

Mesothelioma

Not as dose-related as other asbestos-related diseases, but the risk does increase with dose. Can be found in residents near asbestos mines and with paraoccupational exposure. The percent of patients with confirmed asbestosis will die of mesothelioma (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 second-hand smoke, because exposure to tobacco smoke, especially active smoking, can greatly increase a patient’s risk of lung cancer and can worsen the effects of parenchymal asbestosis.

In addition, it is important to be aware of other respiratory and non-respiratory conditions that may have similar clinical presentations.

Physical Examination

Patients with a history of asbestos exposure should receive a full physical examination. 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 rales with end-inspiratory crackles on pulmonary auscultation. These are typically described as sounding like Velcro (Ross 2003).

Physical examination should also include

• abdominal palpitation, which is used to detect the expanding “doughy” feeling associated with peritoneal mesothelioma.
• digital exam 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.

Differential Diagnosis

Several treatable conditions have symptoms similar to those of asbestos-associated diseases. For this reason, it is important to distinguish between these conditions and such disorders as parenchymal asbestosis (see table), which is not curable (treatment is supportive and symptomatic).

It is also important to distinguish between benign asbestos-associated conditions and 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.

Parenchymal Asbestosis

• Idiopathic pulmonary fibrosis
• Other pneumoconiosis:
  • Talc
  • Silica
  • Titanium
  • Zeolite
• Interstitial pulmonary fibrosis (IPF)
• Hypersensitivity pneumonitis
• Sarcoidosis
• Chronic obstructive pulmonary disease (may produce rales similar to bibasilar rales)
• Drug-related fibrosis
• Other pulmonary diseases of this type

• Rheumatoid arthritis
• Prior thoracic surgery/chest wall configuration
• Left ventricular failure (presents with dyspnea, rales, edema, restriction, and basilar markings on chest film)

Benign asbestos-related pleural disease

Single pleural plaques

• malignant mesotheliomas and metastatic adenocarcinomas (Khan et al. 2004)

Single calcified pleural plaques

• Tuberculosis
• Empyema
• Hemothorax (Khan et al. 2004)

Bilateral calcified pleural plaques

• Most commonly asbestos related but in rare cases
  • Radiation exposure
  • Hyperparathyroidism
  • Pulmonary infarction
  • Pancreatitis (Khan et al. 2004)

Diffuse pleural thickening

• post-exudative effusions such as parapneumonic effusions and those secondary to connective tissue disease
• hemothorax
• mesothelioma, (Khan et al. 2004)

Rounded atelectasis (folded lung)

• Lesions that are similar to 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., 2004)

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. 2004)

Malignant mesothelioma

• Diffuse pleural thickening
• Metastatic adenocarcinoma (Khan et al. 2004; 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 pulmonary auscultation.
• Patients with parenchymal asbestosis present to the clinician with the chief complaint of fatigue, insidious onset of dyspnea on exertion.
• Asbestos-related 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 is typically asymptomatic until later stages, at which point patients have dyspnea and chest pain.

Progress Check