The effect of quartz content on the pathogenicity of coal mine dusts

An inhalation study has been undertaken to examine the relative pathogenicities of coalmine dusts containing different proportions of quartz. To minimise confounding effects the airborne dusts were collected from within a single seam at one colliery. Animals were exposed either to a high (25%) quartz dust, a low (7%) quartz dust, a medium (13%) quartz dust or an alternating regimen of 2 weeks high quartz and 6 weeks low quartz dusts. The respirable dust concentration was 20 mg/m3 in all chambers and exposure lasted 12 or 18 months. Groups of animals were killed immediately after the end of the dusting phase and, thereafter, at 4 monthly intervals. Detailed pathological examinations were undertaken on each animal and lung and lymph node dust burdens and compositions were determined.

The most important differences in response between treatments were in the development of discrete cellular pigmented pulmonary nodules which were most profuse in animals exposed to high quartz dust. Details of these differences and other pathological responses are described in relation to challenge dust composition and the lung and lymph node dust burdens and composition. In addition, some evidence for the inhibition of pulmonary response from continuing dusting was found.