The composition of respirable dust in some British coalmines

The composition of the respirable dusts sampled during the gravimetric surveys at the ten collieries retained for pneunoconiosis field research after the Third Medical survey has been systematically measured by infra-red spoctrophotonetry. This report reviews the comprehensive compositional data which is now available. These Phase 2 compositions are compared with the compositional values derived from interference microscope measurements on thermal precipitator samples collected during the ten-year period prior to the Third Medical Survey and previously reported in the Addenda to the Summary Reports on the Environmental Measurements. Information is also provided to assist any consideration of composition – weighted dust standards.The mean dust compositions during Phase 2 differ considerably between the collieries: the colliery mean values for ash, quartz and kaolin/nica during coalface coalgetting work ranging from circa 11 to 58%, 2 to 9% and 9 to 29% respectively. Broadly similar compositional values were found for dusts sampled during other underground work except for those taken during stonework.On average, the ash and quartz compositions measured for the ‘hard header’ occupational groups and derived values for ‘stone drivages’ (defined by the criteria adopted for routine dust control; were about 40-50% higher than for the corresponding coalface dusts. There is, however, no clear cut distinction between the dust compositions measured during coalwork, where the 8 mg/m3 dust standard applies, or stonework where a 3 mg/m3 standard is applicable (NCB, 1969).The analytical data suggests that stone dusting operations do not generally contribute substantially to the coalface dust concentrations.The Phase 1 compositions for the general environmental classes differ in some respects from the Phase 2 values. Some of these variations are attributed to real changes in conposition with time resulting from changing mining practices or geology. “”