Epidemiology

• High-risk populations include construction trades, joiners, plumbers, electricians, painters, boilermakers, shipyard workers, railroad workers, asbestos miners and Navy veterans.^[4]
• High exposure to asbestos stopped in the USA in the late 1970s (but later in the UK) following government legislation passed after the adverse effects became recognised.^[5]
• The annual number of mesothelioma deaths in the UK is increasing, with 2,156 deaths in 2007 compared with 153 in 1968.^[6]
• The expected number of deaths amongst males is predicted to increase to a peak of 2,038 in the year 2016.^[6]
• The incidence of asbestos-related disease will continue to increase in developing countries because of the continued unregulated use of asbestos.
• Exposure to cigarette smoke increases the risk of developing lung cancer in patients with a history of asbestos exposure.^[4]

Management^[4]

• Some patients are entitled to compensation and should seek advice from the Department for Work and Pensions (see link below) or dedicated charity organisations.
• Smoking cessation is important because smoking increases the risk of developing lung malignancy.
• It has been recommended that chest X-rays and pulmonary function tests should be performed every three to five years in patients with asbestos-related disease.
• Influenza immunisation and pneumococcal immunisation should be given to patients with asbestosis or lung malignancy.

Benign disease

Pleural plaques

• Pleural plaques usually affect the parietal pleura (especially adjacent to the sixth to ninth ribs and along the surface of the diaphragm) and they occur in 20-60% of people who have been exposed to asbestos.^[2]
• Pleural plaques are usually asymptomatic but may cause chest pain. They remain benign and do not become malignant.
• CT scan is more sensitive than a chest X-ray, and distinguishes pleural plaques from solid tumours.

Diffuse pleural thickening^[2]

• Diffuse thickening of the pleura may occur after exposure to asbestos, but other causes include previous haemothorax, tuberculosis, chest surgery, radiation, infection, and exposure to drugs such as methysergide. It is therefore less specific to asbestos exposure than pleural plaques.
• Extensive diffuse pleural thickening may cause breathlessness.
• Chest X-ray findings of diffuse pleural thickening include a smooth continuous pleural density affecting at least 25% of the lateral chest wall, sometimes with blunting of the costophrenic angle.
• Lung function tests may show a restrictive ventilatory defect.
• CT scan and biopsy may be required to differentiate diffuse pleural thickening from mesothelioma.

Benign asbestos-related pleural effusion

• Pleural effusions can occur within 15 years of asbestos exposure but may appear much later.
• A pleural biopsy is usually required to differential between benign and malignant pleural effusions.
• Benign effusions may require drainage if large and symptomatic but they may resolve spontaneously.

Asbestosis

• Asbestosis is a typical pneumoconiosis (interstitial lung disease caused by inhaled inorganic dusts) and is caused by inhalation of asbestos fibres, with a latent period of 20-30 years.
• The development and severity of asbestosis is related to the degree and duration of asbestos exposure.
• Presentation:
  • There is typically an initial gradual onset of breathlessness and reduced exercise tolerance, sometimes with productive cough and wheezing.
  • Progression of asbestosis may lead to fine bilateral inspiratory crackles, finger clubbing and cor pulmonale.
• Investigations:
  • Pulmonary function tests show reduced gas transfer, reduced lung volumes, a restrictive ventilatory defect, and exercise-related hypoxaemia.
  • Chest X-ray may be normal but usually shows bilateral lower zone interstitial changes, often with pleural plaques and thickening.
  • High resolution CT scans are more sensitive than chest X-rays.
  • Biopsy and histological confirmation is not usually required.
• Management:
  • No specific treatment is available.
  • Management therefore includes treatment for chronic obstructive pulmonary disease and cor pulmonale, smoking cessation, influenza and pneumococcal immunisation, and prevention of further exposure to asbestos.
• Prognosis:
  • The prognosis of asbestosis is very variable and depends on the extent of lung involvement and the severity of chronic obstructive pulmonary disease.

Malignant disease

Lung cancer

• Exposure to asbestos causes lung cancer independently of cigarette smoking.^[7]
• Asbestosis need not be present in a person developing lung cancer as a result of asbestos exposure.
• The diagnosis and management are the same as those for all patients with lung cancer.

Mesothelioma

See separate article Malignant Mesothelioma.

Other cancers

Studies have also shown an association between asbestos exposure and cancers of the gastrointestinal tract, throat, kidney and gallbladder, and some types of lymphoma but the evidence is currently inconclusive.^[8]

Compensation

• Patients with asbestos-related lung disease may be eligible for compensation through the Industrial Injuries Disablement Benefit (IIDB) from the Department of Social Security (see link below) or a civil law claim for damages from the employer at the time of asbestos exposure.
• Under the UK Limitation Act 1980, patients have only three years in which to make a civil claim from the date they became aware of the asbestos-related disease caused by an act or omission of the proposed defendant.
• Various charities can also provide help and support on compensation (see Asbestos Victims Support Groups Forum UK link below).