Effect of coal mine dust and clay extracts on the biological activity of the quartz surface

Modification of the quartz surface by aluminium salts and metallic iron have been shown to reduce the biological activity of quartz. This study aimed to investigate the ability of water soluble extracts of coal mine dust (CMD), low aluminium clays (hectorite and montmorillonite) and high aluminium clays (attapulgite and kaolin) to inhibit the reactivity of the quartz surface. DQ12 induced significant haemolysis of sheep erythrocytes in vitro and inflammation in vivo as indicated by increases in the total cell numbers, neutrophil cell numbers, MIP-2 protein and albumin content of bronchoalveolar lavage (BAL) fluid. Treatment of DQ12 with CMD extract prevented both haemolysis and inflammation. Extracts of the high aluminium clays (kaolin and attapulgite) prevented inhibition of DQ12 induced haemolysis, and the kaolin extract inhibited quartz driven inflammation. DQ12 induced haemolysis by coal mine dust and kaolin extract could be prevented by pre-treatment of the extracts with a cation chellator. Extracts of the low aluminium clays (montmorillonite and hectorite) did not prevent DQ12 induced haemolysis, although the hectorite extract did prevent inflammation. These results suggest that CMD, and clays both low and rich in aluminium, all contain soluble components (possibly cations) capable of masking the reactivity of the quartz surface.