Animal inhalation experiments to investigate the significance of high and low percentage concentrations of quartz in coalmine dusts in relation to epidemiology and other biological tests. Final report on CEC Contract 7256-32/019/OS

While there is no doubt that high exposure to relatively pure quartz dust is hazardous to health and may cause silicosis, the Importance of the quartz component of coalmine dust in the development of coalworkers’ pneumoconiosis is much less clear and has been the subject of much research. This report describes a study undertaken by the Institute of Occupational Medicine as part of the second phase of the CEC collaborative programme of research into the role of quartz in the development of coalworkers’ pneumoconiosis. The principal aim of this study was to examine whether increasing fractions of quartz in respirable coalmine dust from the same seam at a single colliery are associated with increasing lung damage in exposed laboratory rats.An inhalation study was undertaken using a series of three coalmine dusts, collected in the same seam within a single colliery with quartz contents between 7% and 25%. The study clearly demonstrated that increasing quartz exposure was associated with increasing lung disease amongst laboratory rats.The nodular lesions which were produced in the lungs of the exposed animals showed many characteristics similar to those observed in coalminers. The results are also consistent with recently published epidemiological studies which have shown strong associations between the progression of pneumoconiosis and the extent of quartz exposure within collieries. However, epidemiological research has also demonstrated clear differences In response to dust exposure at different collieries which cannot be simply explained by variabilities In cumulative dust exposure and dust composition. It has been suggested that some of the effects of dust composition on response may be complicated by other minerals inhibiting the toxic properties of quartz.It is proposed that further animal studies should be carried out to Investigate these differences in response to coalmine dust and the inhibiting effects on quartz. These could be undertaken with real coalmine dusts collected in collieries where similar quartz exposures occur but with different risks of developing pneumoconiosis. Such studies may increase the understanding of the results of epidemiological studies of coalminers and, in the longer term, have important implications for any further consideration of airborne quartz standards in coalmines.