The influence of dust sampling instrumentation and dust composition on the biological activity of coalmine dusts and the estimation of risks of coal workers pneumoconiosis.

The general relationships between cumulative exposures to respirable coalmine dust and the risks of developing simple pneumoconiosis are well established. These relationships, however, do not explain all the variations in risks between coalmining situations and, in particular, the role of quartz is not well understood. A major joint community study of these problems has therefore been undertaken, making use of recent advances in dust sampling, chemical analyses of dust surfaces and biological testing. The aims of the Institute of Occupational Medicine’s contribution were to:(1) To assess the difference in dust composition and particle size between alveolar deposition dusts and respirable dusts collected in British coalmines.(2) To investigate the relationship between dust composition and the ratio of alveolar deposition dust concentrations to respirable dust concentration.(3) To compare the toxicities of dusts collected side by side with respirable and alveolar deposition dust samplers.(4) To compare the toxicities of dusts with different quartz contents collected in a single seam.(5) To provide dust samples for parallel studies in other community laboratories.Dusts from three collieries were used for this study. Two of the collieries were part of the Pneumoconiosis Field Research (PFR) and the relationships between dust exposure and disease are well documented. The third colliery was adjacent to a colliery (now closed) which was part of the PFR and which mined the same coal measures. Two collieries were in South Wales and one in North East England. The coals mined ranged from low/medium rank (86.3% carbon) to anthracite (94.0% carbon). Dust sampling was carried out in two or three locations across one face in each colliery over a period of two or three weeks, depending on the prevailing dust concentrations. Respirable dusts were sampled using the BAT II and MRE gravimetric dust sampler and the TBF50 was used as the alveolar deposition dust sampler. Each individual sample was, if sufficient dust was collected, analysed for its ash, quartz and kaolinite contents. These samples were used to prepare sets of alveolar deposition and respirable dusts with different mineral compositions for each colliery for more detailed mineral analysis (including measurement of the sizes and compositions of individual particles) and biological testing (cytotoxicity, pulmonary inflammation following intratracheal instillation and histological change following intratracheal instillation).The respirable dust concentrations ranged from 0.7 to 17mg/m3. Alveolar deposition dust concentrations were on average lower but there were several exceptions. The compositions of samples collected within collieries differed considerably from day to day. At the colliery in the North East the percentage of quartz in dust ranged from 2.6 to 19.5% and at the other two there was a range of around 6% between highest and lowest percentages of quartz. The dusts from the North East England colliery had compositions consistent with those observed in the earlier pneumoconiosis research. The dusts from both South Wales collieries had much higher non coal mineral and quartz contents than were found in earlier research. The respirable dusts and alveolar deposition dusts had, in general, similar compositions. The relationships between the alveolar deposition dust and respirable dust concentrations were not apparently affected by dust composition.The range of compositions of the dust samples from each colliery enabled three alveolar deposition and three corresponding respirable dusts with different compositions to be prepared from two of the collieries and two pairs of dusts from the third. There were clear differences in the particle sizes of the respirable and alveolar deposition dusts with few particles below 1��m being observed in the latter. For a given dust type coal particles were generally coarser than the other mineral types. Very few coal particles with diameters of more than 5��m were observed. If anything, more of these larger particles were found in the high rank collieries. In general, within each colliery for either alveolar deposition or respirable dust the higher the ash contents of the dust the finer the dust. This also appeared to hold for the coal particles alone.All the respirable and alveolar deposition dusts were found to have low cytotoxicity in the in vitro tests, similar to the non-toxic titanium dioxide controls. The studies of lung inflammation and histological change both indicated that the higher the quartz content of dust from a colliery the greater the damage to the lungs. There were no systematic differences between the biological activities of alveolar deposition and respirable dusts measured using the cytotoxicity or inflammatory assays.In conclusion, the results suggest that measurements of alveolar deposition dust concentration provides no benefit over respirable dust measurements for assessing risks of coal workers pneumoconiosis in British coalminers. The research adds weight to the evidence that as the proportions of quartz within dust within a given seam or colliery increase so do the health risks from exposure to a given respirable dust mass. “”