Previously it was possible to claim compensation for pleural plaques caused by negligent exposure to asbestos, on the grounds that although it is in itself asymptomatic, it is linked to development of diffuse pleural thickening, which causes lung impairment. It has been highly contentious, however, as to the probability of pleural plaques developing into pleural thickening or other asbestos-related illnesses. On October 17, 2007, this point was clarified by the Law Lords' ruling that workers who have pleural plaques as a result of asbestos exposure will no longer be able to seek compensation as it does not in itself constitute a disease. This ruling was, however, superseded, so far as sufferers of pleural plaques in Scotland are concerned, by the passing of the Damages (Asbestos-related Conditions)(Scotland) Act 2009, which provides that in Scots law pleural plaques are to be considered an actionable type of personal injury.