Asbestos-related diseases

The risk of asbestos-related lung disease increases with the duration and degree of exposure and also depends on the type of asbestos fibre. People exposed to asbestos often develop lung disease after a long latent period.¹ Asbestos exposure may cause:²

• Benign disease: pleural plaques, pleural thickening, benign pleural effusions.

• Interstitial lung disease: asbestosis.

• Malignant disease: particularly mesothelioma and lung cancer.

The three main types of asbestos that have been used commercially are crocidolite (blue asbestos), amosite (brown) and chrysotile (white). All fibre types are dangerous. There has been some discussion in the literature that blue and brown asbestos are more dangerous than white. Chrysotile appears to be safer than the other types.³

Alveolar macrophages play a significant role in the aetiology of asbestosis-related diseases.⁴

How common are asbestos-related diseases? (Epidemiology)

• High-risk populations include construction trades, joiners, plumbers, electricians, painters, boilermakers, shipyard workers, railroad workers, asbestos miners and Navy veterans.

• There are around 2,700 new mesothelioma cases in the UK every year (2016-2018). 1 in 212 UK males and 1 in 963 UK females will be diagnosed with mesothelioma in their lifetime.⁵

• The World Health Organization (WHO) has estimated that about 125 million people in the world are currently exposed to asbestos at the workplace. The incidence of asbestos-related disease will continue to increase in developing countries because of the continued unregulated use of asbestos.⁶

• Exposure to cigarette smoke increases the risk of developing lung cancer in patients with a history of asbestos exposure.⁷

Asbestos-related diseases treatment and management

• Some patients are entitled to compensation and should seek advice from the Department for Work and Pensions⁸ or dedicated charity organisations.

• Smoking cessation is important because smoking increases the risk of developing lung malignancy.

• 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.⁹

• Pleural plaques are usually asymptomatic but may cause chest pain. They remain benign and do not become malignant although there is some evidence that they may be an independent risk factor for mesothelioma.¹⁰

• The current evidence indicates that pleural plaques do not impact lung function.¹¹

• CT scan is more sensitive than a CXR and distinguishes pleural plaques from solid tumours.¹²

Diffuse pleural thickening¹³

• Diffuse thickening of the pleura may occur after exposure to asbestos; however, 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.

• CXR 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 10-20 years of asbestos exposure but may appear much later.²

• A pleural biopsy is usually required to differentiate between benign and malignant pleural effusions.

• Benign effusions may require drainage if large and symptomatic but they may resolve spontaneously.

Asbestosis¹⁴

• 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.

• CXR 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 CXRs.

• Biopsy and histological confirmation are not usually required.

Management

• No specific treatment is available.

• Management therefore includes treatment for chronic obstructive pulmonary disease (COPD) 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 COPD.

Malignant disease

Lung cancer

• Exposure to asbestos causes lung cancer independently of cigarette smoking.

• 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.

See also the separate Lung Cancer article.

Mesothelioma

See the separate Malignant Mesothelioma article.

Other cancers

Studies have also shown an association between asbestos exposure and pancreatic cancer.¹⁵

Compensation

• Patients with asbestos-related lung disease may be eligible for compensation through the Industrial Injuries Disablement Benefit (IIDB) from the Department for Work and Pensions⁸ 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 in 'Further reading & references, below).

Medical surveillance

Asbestos-related diseases cannot be prevented in people who work with asbestos. However, its effects can be limited by health and safety measures combined with regular medical surveillance.

The control of industrial asbestos exposure in the UK is subject to the Asbestos Control Regulations 2012. These specify the surveillance regimes required for people working with asbestos. The required schedule varies, depending on the degree of risk to the individual worker.¹⁶ For those at highest risk, a medical check at least every two years is required. This involves an occupational and respiratory history, a respiratory examination and lung function tests. Routine CXRs are no longer performed due to concerns over unnecessary exposure to radiation but are arranged if clinically indicated.