It has recently been suggested that the inhalation of coal in the absence of 
complicated coal workers' pneumoconiosis (CWP) or smoking can lead to disabling 
airways obstruction. The cause of such obstruction has been variously attributed 
to emphysema or bronchitis. The frequency of significant airways obstruction in 
a group of United States coal miners seeking compensation for occupationally 
induced pulmonary impairment was therefore determined. In a sample of 611 "Black 
Lung" claimants there was only one subject who was a non-smoker and who in the 
absence of other non-occupationally related diseases,--for example, asthma and 
bronchiectasis--had sufficient airways obstruction to render it difficult for 
him to carry out hard labour. An alternative explanation for his reduced 
ventilatory capacity other than coal dust or smoking may be available. If the 
inhalation of coal dust in the absence of smoking and complicated CWP ever 
induces sufficient ventilatory impairment to preclude a miner from working, it 
is indeed rare.