Studies on the cytotoxicity of coal dust samples, including the effects of adsorbed nitrous fumes. Final report on CEC Contract 6244-00/8/1055

1. An in vitro test system was developed utilising a permament line of “”macrophage-like”” cells (P388D1) in order to estimate the cytotoxicity of colliery dusts. Some of the colliery dusts were also tested for their ability to damage cell membranes by a haemolytic technique using sheep erythrocytes. This was because other workers have suggested that this is a useful technique for estimating levels of dust cytotoxicity. These techniques were used to examine the cytotoxic effects of dusts from all the working faces of thenine remaining collieries in the National Coal Board’s Pneumoconiosis Field Research Study. In addition, laboratory prepared coal dust samples were examined to estimate the effects of adsorbed nitrous fumes on cytotoxicity.2. All the dusts from a single colliery were tested in the same experiment to minimise biological error and a system ofstatistical analysis was devised to permit comparison between the results of different experiments.3. When the results of all colliery dusts were examined as one group a significant positive correlation was found between high ash content and cytotoxicity (r = 0.34, P < 0.01). Of the individual ash compoments, kaolin and mica showed a bettercorrelation with cytotoxicity than quartz but both of these correlations were numerically lower than that for ash content.The collieries studied fell into two groups when considered in relation to colliery average % carbon; dusts from those collieries ranked above 90% carbon were designated dusts from high rank collieries, and those with less were designated dusts from low rank collieries.When the two groups were examined separately it was found that, for the dusts from high rank collieries, the ash content correlated extremely well with cytotoxicity (r = 0.75, P < 0.001) as did the levels of kaolin and mica (r = 0.58, P < 0.01). In this group quartz also correlated with cytotoxicity but at a lower level of significance (r = 0.48, P < 0.05). With dusts from low rank collieries, the correlation between ash and cytotoxicity was much less although still significant (r = O.4, P < 0.05). However, no significant correlation was seen between the individual ash compoments and cytotoxicity.b. The results obtained when colliery dusts were testedusing the haemolytic system showed that the level of haemolysis correlated significantly with coal rank (r = -0.58, P < 0.05) and with non-coal mineral (r = O.47, P < 0.05) but the only significant correlation found when the compoments of the non-coal mineral were considered was with quartz (r = 0.41, P < 0.05). When the dusts were considered as two groups from either high or low rank collieries, those from the high rank collieries showed a significant increase in haemolysis with increasing amounts of non-coal mineral (r = 0.63, P < 0.05) and this was related to an increasing quartz concentration (r = 0.69, P < 0.05) but not to the increase in kaolin and mica that was found in the cytotoxicity experiments. The only significant correlation that was observed for the dusts from low rank collieries was with coal rank itself (r = -0.48, P < 0.05). The significant differences observed between the results obtained using the haemolytic and cytotoxicity techniques may suggest that more than one in vitro test system may be required to examine cellular damage caused by dusts.5. Results obtained in this study indicated that the mineralcontent and the cytotoxic potential of dusts from the samecolliery can show considerable variation. This variation can apply to different faces working the same coal seam and also to samples from the same working face collected at different times.This means that the cytotoxic potential of the dust from any working situation is unlikely to be accurately estimated by the study of a single sample. These experiments were undertaken in the hope that cytotoxicity estimations might give important nformation on the potential of any mine dust to cause pneumoconiosis. However, no close relationship between cyto toxicity and various measurements of pneumoconiosis risk in the different collieries was observed. This was probably due in part to the variability between samples. The results on the importance of coal rank indicate that the ash content of dustfrom high rank collieries is much more important in the causation of cytotoxicity than the ash content of low rank dusts even though the overall ash content is much higher in low rank collieries and this may have implications on the effects of those dusts in the development of pneumoconiosis.6. The overall results of this study were in good agreement with those of previous studies in that both the rank andcomposition of colliery dusts were found to be of importance whereas the role of quartz remained enigmatic.7. In a series of experiments examining the effects of nitrous fumes, no overall differences in cytotoxicity were found to occur between samples of pure coal dust and samples onto which high levels of nitrogen dioxide had been adsorbed. ""