The role of periodic examination in the prevention of coalworkers' pneumoconiosis.

There can be no doubt that coalworkers' pneumoconiosis presents one of the most serious problems in industrial medicine in Britain, at least in respect of the numbers of men affected. From 1931 up to the end of 1949 some 36,000 men had been officially diagnosed by the Silicosis Medical Board or the Pneumoconiosis Panels of the Ministry of National Insurance as being disabled by the disease. Over 80% of these cases had arisen in the South Wales coalfield. The social consequences of the disease in South Wales have been reviewed by Hugh-Jones and Fletcher (1950). The cost of the disease in terms of compensation has been enormous and in terms of human suffering immeasurable. The disease is one that has been shown to be due to the inhalation of coal dust (Hart and Aslett, 1942) and its ultimate control and prevention will come from dust suppression. Airborne dust concentrations underground must be reduced to levels at which they will not cause pneumoconiosis in men exposed to them throughout a normal working life. Coal dust in some mines appears to be less dangerous than in others. But since the factors which may make coal dust dangerous are not yet known, the precise levels of dust concentration in different pits which may be regarded as safe are uncertain, and indeed they cannot be established until a generation of coal miners has been exposed to them for their working life and has been shown to remain healthy. At present the Ministry of Fuel and Power and the National Coal Board have accepted as provisional levels for " approved dust conditions " under which men may be expected to work with reasonable safety, 650 particles/cc.* between 1 and 5 microns in anthracite pits and 850 particles/cc., within the same size range, in steam and bituminous coal pits. This expectation is, however, based on scanty evidence (Bedford and Warner, 1942), and the approved dust levels