Pleural thickening is a lung disease that describes a scarring, calcification, and/or thickening of the pleura (the lining surrounding the lungs) often as a consequence of the inhalation of asbestos into the lungs. If the asbestos fibres work their way into the pleura, they can cause the pleural thickening condition. Pleural thickening tends to cause sufferers a tightness of the chest or breathlessness which is attributed to the reduced lung function that the thickening causes.

Pleural plaques are caused in much the same way as pleural thickening but they are localised and the sufferer usually does not get the symptoms that a sufferer of pleural thickening would. In fact it is entirely possible that people with pleural plaques can live with the condition undiagnosed with no problems for the remainder of their lives.