Heterogeneity in coal composition and the implications for the lung cancer risk in XuanWei and Fu Yuan, China

摘要

Background: Xuanwei and Fuyuan counties in Yunnan province, China have the highest lung cancer rates in China. This has been associated with the domestic use of locally sourced "smoky" (bituminous) coal. Significant geographical variation in cancer rates has also been observed, suggesting heterogeneity in fuel source composition and/or combustion characteristics. Relatively little is known as yet about heterogeneity in coal composition in the region. Limited research thus far has indicated that the coal in the region contains notably high levels of organics, notably polycyclic aromatic hydrocarbons and free crystalline silica. Methods: Coal samples were collected as part of a large cross-sectional molecular epidemiology study throughout the XuanWei and FuYuan areas. Coal samples were analysed for a variety of characteristics including: petrochemical potential, trace elements, carbon-sulphur and mineralogical components. Results: 146 samples were retrieved from participating households. Analysis revealed significant differences between smoky and smokeless coal with regard to petrochemical potential, trace elements, carbon-sulphur and mineralogy. Of note, smoky coal contained higher levels of hydrocarbons and quartz and lower levels of aluminium than smokeless coal. Further significant variation was observed for hydrocarbons and trace elements (including aluminium and silicon)on the basis the geographical source of the coal. Discussion: Our findings indicate that clear and measurable differences exist between smoky and smokeless coals sourced from Xuanwei and Fuyuan districts as well as a significant degree of heterogeneity within coal types. Decreased aluminium may indicate elevated free silica, which would be consistent with the observed higher levels of quartz. Elevated hydrocarbons would be consistent with previous observations of elevated polycyclic aromatic hydrocarbons in coals from the area. Future research is required to establish which (if any) of the observed differences translate into indoor air pollution and cancer risk.