Abstract
A sample of some 30,000 men working at 25 selected collieries distributed throughout the British coalfields is being examined over a period of upwards of ten years. Continuous measurements of environmental conditions are being made at all the collieries, and medical surveys, including radiological examinations, are carried out at intervals of about five years. The present paper shows how the progression of pneumoconiosis as revealed by the radiological examinations is correlated with the individual estimates of dust exposure. The main principles on which the methods of correlation are based are described and it is shown how the available data may be employed to determine “safe levels of dustiness.”