The oxidative potential of PM10 from coal, briquettes and wood charcoal

Coal contains many potentially harmful trace elements. Coal combustion in 22 unvented stoves, which is common in most parts of rural China, can release harmful emissions 23 into the air that when inhaled cause health issues. However, few studies have dealt specifically 24 with the toxicological mechanisms of the particulate matter (PM) released by coal and other 25 solid fuel combustion. In this paper, PM10 particles that were generated during laboratory stove 26 combustion of raw powdered coal, clay-mixed honeycomb briquettes, and wood charcoal were 27 analysed for morphology, trace element compositions, and toxicity as represented by oxidative 28 DNA damage. The analyses included Field Emission Scanning Electron Microscopy (FESEM), 29 Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Plasmid Scission Assay (PSA). 30 Gravimetric analysis indicated that the equivalent mass concentration of PM10 emitted by 31 burning raw powdered coal was higher than that derived by burning honeycomb coal. FESEM 32 observation revealed that the coal burning-derived PM10 particles were mainly soot aggregates. 33 The PSA results showed that the PM10 emitted by burning honeycomb briquettes had a higher 34 oxidative capacity than that from burning raw powdered coal and wood charcoal. It is also 35 demonstrated that the oxidative capacity of the whole particle suspensions were similar to those 36 of the water soluble fractions; indicating that the DNA damage induced by coal burning-derived 37 PM10 were mainly a result of the water-soluble fraction. An ICP-MS analysis revealed that the 38 amount of total analysed water-soluble elements in the PM10 emitted by burning honeycomb 39 briquettes was higher than that in PM produced by burning raw powdered coal, and both were 40 higher than PM from burning wood charcoal. The total analysed water-soluble elements in 41 these coal burning-derived PM10 samples had a significantly positive correlation with the level 42 of DNA damage; indicating that the oxidative capacity of the coal burning-derived PM10 was 43 mainly sourced from the water soluble elements. The water-soluble As, Cd, Ge, Mn, Ni, Pb, 44 Sb, Se, Tl, and Zn showed the highest correlation with the oxidative potential, implying that 45 these elements in their water soluble states were the primary responsible factor for the plasmid 46 DNA damage. The exposure risk was further assessed using the particle mass concentrations 47 multiplied by the percent of DNA damage under the dose of 500 μg ml. The results revealed 48 that the exposure risk of burning raw powdered coal was much higher than that of burning 49 honeycomb coal. 50