What is asbestos?

Asbestos is a naturally occurring fibre, which is mined in various parts of the world, notably South Africa and Canada. It occurs in three forms known as blue, brown and white asbestos. It can be used in different ways for industrial reasons, and its resistance to heat, electricity and sound makes it useful for a variety of purposes, particularly as insulation and brake-linings. Unfortunately, asbestos can be hazardous to someone's health and it is for this reason why the use of asbestos has declined considerably in recent years.

What is asbestosis?  

Asbestosis is a type of fibrous or scarring of the lungs caused by asbestos fibres, which have lodged in the lungs after being inhaled from the air. The fibrosis causes the lungs to shrink, resulting in breathlessness. 

Asbestosis develops in some people who have breathed in a substantial amount of asbestos dust over the course of their work. It usually shows itself a long time after inhalation of the dust, often 20 or 30 years since the start of the exposure.

Other diseases caused by asbestos

Asbestos causes a number of diseases other than asbestosis. The term ‘asbestosis’ is commonly used by the media to refer to any disease caused by asbestos, and this can lead to confusion. Other conditions can include pleural thickening, mesothelioma and lung cancer.

Pleural thickening 

The pleura is a two-layered membrane which surrounds the lungs and lines the inside of the rib cage. Some asbestos fibres inhaled into the lungs work their way out to the pleura, and may cause fibrosis or scarring to develop there. This leads to the thickening of the pleura which may show up on a chest X-ray.

Pleural thickening occurs in two forms. Diffuse pleural thickening extends over a large area and may restrict expansion of the lungs, leading to breathlessness. Whereas pleural plaques are localised areas of thickening, which usually do not interfere with breathing.


Mesothelioma is a malignant tumour which starts in the pleura or the peritoneum, the lining of the abdominal cavity. Asbestos and other similar fibres which are found in the soil in some parts of the world are the only known causes of mesothelioma. The risk of mesothelioma is highest in those who have been heavily exposed to asbestos, but the condition occasionally occurs in people who have had relatively light exposure.

Lung cancer

Exposure to asbestos can increase the risk of developing lung cancer. A very important point is that asbestos exposure and smoking can act together to produce a huge risk of lung cancer in people exposed to both hazards. People who have been exposed to asbestos can greatly reduce the risk of lung cancer by not smoking.


Strict regulations now exist to prevent people being exposed to dangerous levels of asbestos.  

Asbestos in buildings

Asbestos is still present in a wide variety of buildings, often in the walls and ceilings along with lagging around steam pipes and boilers. Discovery of asbestos in a building often causes alarm among people living or working in it. Usually this alarm is not justified. Providing the asbestos is well maintained and preferably covered by an impermeable layer of paint or other material, so that it is not releasing dust, it does not present any hazard to health. It is only the inhalation of loose asbestos fibres which causes disease.

Occupational lung disease team contact information


Department of Occupational and Environmental Medicine, Emmanuel Kaye Building, 1B Manresa Road, London, SW3 6LR

Tel: 020 7351 8341
Fax: 020 7351 8336 

Useful information

Visit the Lungs at Work website - this website has more information about what to expect from your appointment with the team, and all the research carried out by them.