Further studies on the importance of quartz in the development of coalworkers’ pneumoconiosis. Final report on CEC/BCC project 7248-33-044

1. Coalworkers’ pneumoconiosis is known to be related to the mass of coalmine dust inhaled but differences in dust composition create anomalies that are at present not fully understood. Thus, while quartz is known to be a very pathogenic material, the mass and proportion of quartz in inhaled dust does not always relate closely to the occurrence of pneumoconiotic nodules. The reasons for this are uncertain but there have been suggestions that free quartz surface, rather than total quartz, is related to disease development or that some dusts contain minerals that protect against the effects of quartz. The illite group of clay minerals has been particularly mentioned in this context.2. The present study was undertaken using rats in order to examine the ability of coalmine dusts containing similar high quartz levels but different amounts of other minerals to produce pneumoconiosis. The rats were exposed by inhalation.3. Large amounts of dust were collected from two British coalmines, one in Nottinghamshire where miners are known historically to have very low levels of pneumoconiosis, and one in Scotland which had mined a seam associated with a rapidly progressing pneumoconiosis of silicotic type. The dusts from the two mines contained similar proportions of quartz but very different levels of illite.4. Batches of dust for use in the inhalation experiments were produced by mixing individually collected bulk samples from the Nottinghamshire and Scottish coalmines respectively. The respirable dust from the Nottinghamshire mixture contained 15.7% quartz, 18.6% kaolinite and 32% illite, while the respirable fraction from the Scottish dust contained 18.4% quartz, 25.5% kaolinite and 17.0% illite.5. Airborne dust clouds were generated in whole body inhalation chambers at 20mg/m3 respirable dust. The rats were exposed for seven hours a day, five days a week for periods of up to 18 months.6. To examine the development of pulmonary pathology, rats were exposed to dust for either 12 or 18 months with follow up times of 16 and 10 months respectively. To study the development of early pulmonary inflammation, rats were exposed for periods of up to 30 days with a 30 day recovery period. “”