The respiratory toxicity of coal fly ash

The aim of this study was to compare the relative respiratory toxicity of CFA samples obtained from three Chinese coal-burning power stations to CFA obtained from a UK coal-burning power station; both bulk and respirable PM10 samples were tested. In order to elucidate CFA toxicity, a multi-disciplinary approach was taken, thereby considering geochemical aspects of the fly ash as well as biochemical properties. Geochemical analysis was used to determine the composition, morphology and solubility of metallic components. Total analysis, carried out using FLUXY ICP-MS, identified the bulk elements present, X-ray diffraction (XRD) identified crystalline phases present in the particles, and the overall morphology was evaluated by scanning electron microscopy (SEM). Three in vitro biochemical techniques were used to elucidate the samples relative bioreactivity. The samples were tested on their capability to a) generate reactive oxygen species (ROS), using a DCFH assay, b) cause haemolysis of red blood cells (RBCs) via a haemolysis assay, and c) cause damage to plasmid DNA, by use of a plasmid scission assay (PSA). The geochemical analysis showed the samples differ very little in composition between bulk and PM10 fractions and the overall solubility of metals was low (Figure 2). XRD identified the presence of mullite (Figure 3) in all samples with increased levels seen in one particular Chinese sample. SEM showed the particles to be spherical in shape and respirable in size, with 18% of the UK PM10 samples in the fine particle size range, able to reach the most distal regions of the respiratory system. Figure 2. Elemental composition of a UK PM10 fly ash sample. The level of leachable metals is very low.