Heterogeneity in coal composition and implications for lung cancer risk in Xuanwei and Fuyuan counties, China.

Xuanwei and Fuyuan counties in Yunnan Province, China have among the highest lung cancer rates in the country. This has been associated with the domestic combustion of bituminous coal (referred to as "smoky" coal). Additionally, significant geographical variation in cancer rates among smoky coal users has been observed, suggesting heterogeneity in fuel source composition and/or combustion characteristics. Research thus far has indicated that smoky coal emits high levels of polycyclic aromatic hydrocarbons (PAHs) and contains high concentrations of fine grained crystalline quartz, however, much of this research is limited in terms of sample size and geographic scope. In order to more fully characterise geochemical and elemental compositions of smoky and smokeless coal use in Xuanwei and Fuyuan, we carried out a large exposure assessment study in households in this region. Fuel samples representing smoky and "smokeless" (anthracite, the major alternative coal type in the region) coals were collected from 137 homes in Xuanwei and Fuyuan. Rock-Eval, Leco-CS, XRF analysis and electron microscopy were used to establish hydrocarbon content (to represent volatile organic compounds), major and trace element composition and mineral composition respectively. Heterogeneity in coal characteristics between and within coal types was assessed by the Kruskal-Wallis test. 145 coal samples (116 smoky and 29 smokeless coals) were analysed. Statistically significant differences between smoky and smokeless coals with regard to hydrocarbon content, sulfur, trace elements and mineral composition were observed. Of note, smoky coal contained between 5 and 15 times the amount of volatile organic matter and twice the amount of quartz (including respirable quartz) than smokeless coal. Smoky coal generally had lower levels of trace elements (plus aluminium) than smokeless coal. Significant variation was also observed between smoky coal samples from different geographical areas with regard to hydrocarbon content and elemental composition (including aluminium and silicon). This paper has identified compositional differences between and within smoky and smokeless coals sourced from Xuanwei and Fuyuan counties. A decreased ratio of aluminium to silicon in smoky coal suggests elevated free silica, a finding consistent with observed higher levels of quartz. Elevated volatile organic matter content in smoky coal (when compared to smokeless coal) is consistent with the geochemical expectations for smoky and smokeless coals. These findings also reflect previous observations of elevated volatile compound emissions (notably PAHs) from smoky coal in the area. The observed heterogeneity in coal composition between and within coal types may provide leads to the observed heterogeneity in cancer risk observed in this area.

Downward GS ，Hu W ，Large D ，Veld H ，Xu J ，Reiss B ，Wu G ，Wei F ，Chapman RS ，Rothman N ，Qing L ，Vermeulen R ... -  《-》

Quartz in ash, and air in a high lung cancer incidence area in China.

Exposure to crystalline silica (quartz) has been implicated as a potential cause of the high lung cancer rates in the neighbouring counties of Xuanwei and Fuyuan, China, where the domestic combustion of locally sourced "smoky" coal (a bituminous coal) is responsible for some of the highest lung cancer rates in the nation, irrespective of gender or smoking status. Previous studies have shown that smoky coal contains approximately twice as much quartz when compared to alternative fuels in the area, although it is unclear how the quartz in coal relates to household air pollution. Samples of ash and fine particulate matter (PM2.5) were collected from 163 households and analysed for quartz content by Fourier transformed infrared spectroscopy (FT-IR). Additionally, air samples from 12 further households, were analysed by scanning electron microscopy (SEM) to evaluate particle structure and silica content. The majority (89%) of household air samples had undetectable quartz levels (<0.2 μg/m3) with no clear differences by fuel-type. SEM analyses indicated that there were higher amounts of silica in the smoke of smoky coal than smokeless coal (0.27 μg/m3 vs. 0.03 μg/m3). We also identified fibre-like particles in a higher concentration within the smoke of smoky coal than smokeless coal (5800 fibres/m3 vs. 550 fibres/m3). Ash analysis suggested that the bulk of the quartz in smoky coal went on to form part of the ash. These findings indicate that the quartz within smoky coal does not become adequately airborne during the combustion process to cause significant lung cancer risk, instead going on to form part of the ash. The identification of fibre-like particles in air samples is an interesting finding, although the clinical relevance of this finding remains unclear.

Downward GS ，Hu W ，Rothman N ，Reiss B ，Tromp P ，Wu G ，Wei F ，Xu J ，Seow WJ ，Chapman RS ，Lan Q ，Vermeulen R ... -  《-》

Polycyclic aromatic hydrocarbon exposure in household air pollution from solid fuel combustion among the female population of Xuanwei and Fuyuan counties, China.

Downward GS ，Hu W ，Rothman N ，Reiss B ，Wu G ，Wei F ，Chapman RS ，Portengen L ，Qing L ，Vermeulen R ... -  《-》

Lung cancer risk by geologic coal deposits: A case-control study of female never-smokers from Xuanwei and Fuyuan, China.

Coal types vary around the world because of geochemical differences in their source deposits; however, the influence of coal emissions from different deposits on human health remains unexplored. To address this issue, we conducted the first study of the relationship between coal use from various deposits and lung cancer risk in Xuanwei and Fuyuan, counties in China where lung cancer rates are among the highest in the world among female never-smokers due to use of bituminous ("smoky") coal for heating and cooking. We conducted a population-based case-control study of 1031 lung cancer cases and 493 controls among never-smoking women in Xuanwei and Fuyuan. Logistic regression models were used to estimate associations between coal use from various deposits across the lifecourse and lung cancer risk. There was substantial heterogeneity in risks by coal deposit (p = 7.8E-05). Compared to non-smoky coal users, risks by smoky coal deposit ranged from OR = 7.49 (95% CI: 3.43-16.38) to OR = 33.40 (95% CI: 13.07-85.34). Further, women born into homes that used smoky coal and subsequently changed to non-smoky coal had a higher risk (OR = 10.83 (95% CI: 4.61-25.46)) than women born into homes that used non-smoky coal and changed to smoky coal (OR = 4.74 (95% CI: 2.03-11.04, pdifference = 0.04)). Our study demonstrates that various sources of coal have considerably different impact on lung cancer in this population and suggests that early-life exposure to carcinogenic emissions may exert substantial influence on health risks later in life. These factors should be considered when evaluating the health risks posed by exposure to coal combustion emissions.

Wong JYY ，Downward GS ，Hu W ，Portengen L ，Seow WJ ，Silverman DT ，Bassig BA ，Zhang J ，Xu J ，Ji BT ，Li J ，He J ，Yang K ，Tian L ，Shen M ，Huang Y ，Vermeulen R ，Rothman N ，Lan Q ... -  《-》

Characterization of outdoor air pollution from solid fuel combustion in Xuanwei and Fuyuan, a rural region of China.

Hu W ，Downward G ，Wong JYY ，Reiss B ，Rothman N ，Portengen L ，Li J ，Jones RR ，Huang Y ，Yang K ，Chen Y ，Xu J ，He J ，Bassig B ，Seow WJ ，Hosgood HD ，Zhang L ，Wu G ，Wei F ，Vermeulen R ，Lan Q ... -  《-》