Mortality of Dutch coal miners in relation to pneumoconiosis , chronic obstructive pulmonary disease

EDITOR,—Meijers et al presented a very interesting study on mortality of Dutch coal miners. Most of the coal miners, 3367 out of 3790 (89%), had radiological manifestations of coal workers’ pneumoconiosis (CWP). All the coal miners had an increased mortality due to ischaemic heart disease (IHD) in all four periods of follow up when compared with the total male population in the Netherlands. The increase varied between 10% and 25%. It was unlikely that smoking habits were responsible for this increase as the SMR for lung cancer was 1.02. Fibrinogen is an established risk factor for IHD 3 and it has been found that coal miners with pneumoconiosis have higher plasma concentrations of fibrinogen than coal miners without pneumoconiosis. Thus it seems that these findings on coalminers with pneumoconiosis could also be included in the hypothesis linking exposure to dust with increased concentrations of plasma fibrinogen and IHD. The hypothesis of exposure through inhaled particles and the occurrence of IHD can be expressed in the following way. Long term inhalation of particles retained in the lungs will create a low grade inflammation associated with an increase in plasma fibrinogen. The high concentrations of fibrinogen will increase the likelihood of blood clotting and thereby the risk for myocardial infarction and IHD. 6