Royal Naval dockyards asbestosis research project: nine-year follow-up study of men exposed to asbestos in Devonport Dockyard.

Progression of asbestos-related disease was assessed in a group of 253 dockyard workers examined in 1966 and 1975. Despite the almost complete protection from exposure to asbestos since 1966, radiographic parenchymal abnormalities increased and occurred more frequently during the next 9 years in those men who had been more heavily exposed to asbestos. Lung function values were lower in those most heavily exposed and were declining at a faster rate than in those with less dust exposure. The most sensitive lung function index was the transfer factor.Those men with persistent crackles in 1966 exhibited a restrictive pattern of lung function, whereas an obstructive pattern was seen in men with wheezes in 1966. The men with irregular small opacities of category 1/1 or more or with diffuse pleural change in 1966 and who survived to 1975 had worse lung functions than any other groups.Progression of disease was greater for smokers than non-smokers, with those who gave up smoking between 1966 and 1975 suffering the greatest changes. This latter group showed most increase in small opacities and included almost all new cases of diffuse pleural changes. They also showed the greatest declines in forced expiratory volume and forced vital capacity.