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


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands. Electronic address: g.s.downward@uu.nl.
George S
GS
Downward
Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA.
Wei
W
Hu
Department of Chemical and Environmental Engineering, University of Nottingham, UK.
David
D
Large
Deltares, Department of Applied Microbiology and Geochemistry, Utrecht, The Netherlands.
Harry
H
Veld
Department of Community Medicine, School of Public Health, The University of Hong Kong, Hong Kong.
Jun
J
Xu
Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands.
Boris
B
Reiss
China National Environmental Monitoring Centre, Beijing, China.
Guoping
G
Wu
China National Environmental Monitoring Centre, Beijing, China.
Fusheng
F
Wei
College of Public Health Sciences, Chulalongkorn University, Bangkok, Thailand.
Robert S
RS
Chapman
Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA.
Nat
N
Rothman
Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, DHHS, Bethesda, MD, USA.
Lan
L
Qing
Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht, The Netherlands.
Roel
R
Vermeulen
D000393:Air Pollutants / Q000009:adverse effects / Q000737:chemistry; D016022:Case-Control Studies; D002681:China; D003031:Coal / Q000032:analysis*; D003430:Cross-Sectional Studies; D006801:Humans; D006838:Hydrocarbons / Q000032:analysis; D008175:Lung Neoplasms / Q000453:epidemiology*; D008670:Metals / Q000032:analysis; D011791:Quartz / Q000032:analysis; D012307:Risk Factors; D013455:Sulfur / Q000032:analysis; D014131:Trace Elements / Q000032:analysis; D055549:Volatile Organic Compounds / Q000032:analysis
D000393:Air Pollutants; D003031:Coal; D006838:Hydrocarbons; D008670:Metals; D014131:Trace Elements; D055549:Volatile Organic Compounds; D011791:Quartz; D013455:Sulfur
Coal; Exposure assessment; Lung cancer; Solid fuels