Smokeless Coal Research Articles

Personal and indoor PM2.5 exposure from burning solid fuels in vented and unvented stoves in a rural region of China with a high incidence of lung cancer.

The combustion of biomass and coal is the dominant source of household air pollution (HAP) in China, and contributes significantly to the total burden of disease in the Chinese population. To characterize HAP exposure related to solid fuel use and ventilation patterns, an exposure assessment study of 163 nonsmoking female heads of households enrolled from 30 villages was conducted in Xuanwei and Fuyuan, two neighboring rural counties with high incidence of lung cancer due to the burning of smoky coal (a bituminous coal, which in health evaluations is usually compared to smokeless coal—an anthracite coal available in some parts of the area). Personal and indoor 24-h PM2.5 samples were collected over two consecutive days in each household, with approximately one-third of measurements retaken in a second season. The overall geometric means (GM) of personal PM2.5 concentrations in Xuanwei and Fuyuan were 166 [Geometric Standard Deviation (GSD):2.0] and 146 (GSD:1.9) μg/m3, respectively, which were similar to the indoor PM2.5 air concentrations [GM(GSD):162 (2.1) and 136 (2.0) μg/m3, respectively]. Personal PM2.5 was moderately highly correlated with indoor PM2.5 (Spearman r = 0.70, p < 0.0001). Burning wood or plant materials (tobacco stems, corncobs etc.) resulted in the highest personal PM2.5 concentrations (GM:289 and 225 μg/m3, respectively), followed by smoky coal, and smokeless coal (GM:148 and 115 μg/m3, respectively). PM2.5 levels of vented stoves were 34–80% lower than unvented stoves and firepits across fuel types. Mixed effect models indicated that fuel type, ventilation, number of windows, season, and burning time per stove were the main factors related to personal PM2.5 exposure. Lower PM2.5 among vented stoves compared with unvented stoves and firepits is of interest as it parallels the observation of reduced risks of malignant and nonmalignant lung diseases in the region.

The potential role of lung microbiota in lung cancer attributed to household coal burning exposures.

Bacteria influence site-specific disease etiology and the host's ability to metabolize xenobiotics, such as polycyclic aromatic hydrocarbons (PAHs). Lung cancer in Xuanwei, China has been attributed to PAH-rich household air pollution from burning coal. This study seeks to explore the role of lung microbiota in lung cancer among never smoking Xuanwei women and how coal burning may influence these associations. DNA from sputum and buccal samples of never smoking lung cancer cases (n = 8, in duplicate) and controls (n = 8, in duplicate) in two Xuanwei villages was extracted using a multi-step enzymatic and physical lysis, followed by a standardized clean-up. V1-V2 regions of 16S rRNA genes were PCR-amplified. Purified amplicons were sequenced by 454 FLX Titanium pyrosequencing and high-quality sequences were evaluated for diversity and taxonomic membership. Bacterial diversity among cases and controls was similar in buccal samples (P = 0.46), but significantly different in sputum samples (P = 0.038). In sputum, Granulicatella (6.1 vs. 2.0%; P = 0.0016), Abiotrophia (1.5 vs. 0.085%; P = 0.0036), and Streptococcus (40.1 vs. 19.8%; P = 0.0142) were enriched in cases compared with controls. Sputum samples had on average 488.25 species-level OTUs in the flora of cases who used smoky coal (PAH-rich) compared with 352.5 OTUs among cases who used smokeless coal (PAH-poor; P = 0.047). These differences were explained by the Bacilli species (Streptococcus infantis and Streptococcus anginosus). Our small study suggests that never smoking lung cancer cases have differing sputum microbiota than controls. Further, bacteria found in sputum may be influenced by environmental exposures associated with the type of coal burned in the home.

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

BackgroundXuanwei 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. MethodsFuel 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. Results145 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). DiscussionThis 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.

The link between lung cancer and indoor air pollution

www.thelancet.com/oncology Vol 13 October 2012 e415 A retrospective cohort study of more than 37 000 residents of Xuanwei County in China’s Yunnan Province has concluded that the domestic use of smoky (bituminous) coal substantially increases the risk of lung cancer. The study—led by scientists at the National Cancer Institute (NCI), Bethesda, MD, USA—found that male users of smoky coal had an 18% absolute risk of dying from lung cancer before they reached the age of 70 years. Female users, nearly all of whom were non-smokers, had a 20% risk. Male and female users of smokeless coal (anthracite), by contrast, had a lung cancer risk of less than 0·5%. “Lung cancer alone accounted for about 40% of all deaths before age 60 among individuals using smoky coal”, wrote the authors. About half the world’s population relies on solid fuels or coal for cooking and heating. The International Agency for Research on Cancer (IARC; Lyon, France) classifi es indoor emissions from the combustion of coal as a group 1 carcinogen. 2 years ago the UN Foundation launched the Global Alliance for Clean Cook Stoves, aiming to ensure universal access to such devices. In China, where most people live in rural areas, the use of coal is especially prevalent. Moreover, households in Xuanwei, which has some of the highest lung cancer rates in the world, are poorly ventilated, so the internal concentration of coal smoke is particularly intense. “There are several factors that come together in Xuanwei, but the risk for lung cancer in using smoky coal, compared with smokeless coal, is much higher”, co-author Qing Lan (NCI) told The Lancet Oncology. The study period (1976–96) saw a total of 8976 deaths, 2377 of which were due to lung cancer. Co-author Nathaniel Rothman (NCI) described the fi ndings as a “striking example of an environmental contribution to cancer”. Lan added that “the use of less carcinogenic types of coal or other fuels would likely translate to a substantial reduction in lung cancer risk in Xuanwei”. However, this strategy might not always be feasible: good quality coal might not be locally available. Fortunately, other interventions can be highly eff ective. “Construct a chimney and ensure that people’s exposure to coal smoke is reduced”, urges IARC’s Robert Baan. Indeed, an earlier study co-authored by Lan showed that simply installing a household stove with a chimney can halve the risk of lung cancer.

Risk of lung cancer associated with domestic use of coal in Xuanwei, China: retrospective cohort study

Objective To estimate the risk of lung cancer associated with the use of different types of coal for household cooking and heating.Setting Xuanwei County, Yunnan Province, China.Design Retrospective cohort study...

Descriptive study of the environmental epidemiology of high lung cancer incidence rate in Qujing, Yunnan, China

背景与目的我国云南省东北部的曲靖是全世界肺癌高发地区之一，当地居民长期暴露在燃煤烟气中，本研究旨在全面了解我国云南曲靖肺癌高发区的环境背景和污染情况，为肺癌病因学研究提供科学依据，同时也为改善环境状况提供数据支持。方法采用多阶段、分层、整群、概率抽样方法随机抽取280个自然村，了解当地自然村使用燃料的种类、附近有无炼焦厂、铁锌厂、化工厂等环境背景和污染情况，并采用二项Logistic回归分析方法对调查因素进行分析。结果高发区78.1%的自然村使用烟煤和焦煤，低发区78.8%的自然村使用无烟煤和木柴。二项Logistic回归分析方法显示，上述因素中仅有燃料种类进入方程（P < 0.05），烟煤和焦煤的使用与肺癌高发具有正关联作用，而使用木柴、无烟煤不会对肺癌的高发产生影响。结论当地居民使用燃料类型是影响肺癌高发的重要因素，其中烟煤和焦煤对当地肺癌高发有促进作用，而无烟煤或者木柴作用不大或有抑制作用。

Abstract 1876: Assessment of exposure to potential lung carcinogens in Xuanwei and Fuyuan, China: Particulate exposure from cooking and heating stoves

Abstract Residents in Xuanwei, China have the highest lung cancer incidence rates in China for both men and women, despite the fact that almost all women are non-smokers. Several lines of research have provided strong support that the excess lung cancer rate in this region is caused primarily by emissions from smoky coal exposure. We have carried out a hospital-based case-control study of non-smoking female lung cancer in Xuanwei and its neighboring county, Fuyuan, to identify which constituents of coal combustion emissions and other indoor environmental exposures are causing the high lung cancer rates in this region. In order to develop individual estimates of exposure to known or suspected lung carcinogens, we designed a comprehensive exposure assessment study of 163 households in this region to evaluate exposure to PAHs, PM2.5, silica, and other exposures from coal and wood burning. Homes that used three main fuel types (i.e., smoky coal, smokeless coal and wood), and eight stove types [e.g., firepit, fixed or portable stove, with or without ventilation] were identified and households were sampled on two consecutive days. Up to 30 households were selected for each combination of fuel and stove type. A subgroup of 53 households was measured at two time-points during the study year (e.g. summer and winter). The female head of each household was asked to wear a 24-hour personal PM2.5 air sampler at the same time that 24-hour area air sampling was employed in the main living area. Personal and area particulate matter samples (PM2.5) were collected in each home. These samples were also used to quantify particle bound PAHs including BaP (by GC/MS), elemental components (by XRF and ICP/MS), and silica (by XRD). XAD2 samples were collected for the quantification of gaseous PAHs. Other samples, including radon and organic vapor, fuel and ash were also obtained. We also collected information on potential factors that could influence exposure, such as house characteristics, stove type, fuel type and use, amount of fuel used, amount of time spent in each room. Initial analyses show that people using wood burned in firepits were exposed to the highest levels of PM2.5 measured in area (536.3±370.5 µg/m3) and personal samples(419.8±283.3 µg/m3). Burning smokeless coal in a high stove with a chimney was associated with the lowest exposure to PM2.5 (62.2±34.1 µg/m3, 62.5±29.9 µg/m3 for area and personal samples, respectively). These data show that there is a wide range of exposure to PM2.5 in this population. These data and other exposure information from this study will be used in the future to model environmental exposures and risk of lung cancer in this special, high risk population. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1876. doi:10.1158/1538-7445.AM2011-1876

The use of polar organic compounds to estimate the contribution of domestic solid fuel combustion and biogenic sources to ambient levels of organic carbon and PM 2.5 in Cork Harbour, Ireland

PM 2.5 samples collected at Cork Harbour, Ireland during summer, autumn, late autumn and winter, 2008–2009 were analyzed for polar organic compounds that are useful markers for aerosol source characterization. The determined compounds include tracers for biomass burning primary particles, fungal spores, markers for secondary organic aerosol (SOA) from isoprene, α-/ β-pinene, and d-limonene. Seasonal and temporal variations and other characteristic features of the detected tracers are discussed in terms of aerosol sources and processes. The biogenic species were detected only during the summer period where the contributions of isoprene SOA and fungal spores to the PM 2.5 organic carbon (OC) were estimated to be 1.6% and 1% respectively. The biomass burning markers, and in particular levoglucosan, were present in all samples and attributed to the combustion of cellulose-containing fuels including wood, peat, bituminous and smokeless coal. The contribution of domestic solid fuel (DSF) burning to the measured OC mass concentration was estimated at 10.8, 50, 66.4 and 74.9% for summer, autumn, late autumn and winter periods, respectively, based on factors derived from a series of burning experiments on locally available fuels. Application of an alternative approach, namely principal component analysis–multiple linear regression (PCA–MLR), to the measured concentrations of the polar organic marker compounds used in conjunction with real-time air quality data provided similar trends and estimates for DSF combustion during all seasons except summer. This study clearly demonstrates that, despite the ban on the sale of bituminous coal in Cork and other large urban areas in Ireland, DSF combustion is still the major source of OC during autumn and winter periods and also makes a significant contribution to PM 2.5 levels. The developed marker approach for estimating the contribution of DSF combustion to ambient OC concentrations can, in principle, also be applied to other locations.

Coal Use, Stove Improvement, and Adult Pneumonia Mortality in Xuanwei, China: A Retrospective Cohort Study

BackgroundIn Xuanwei County, China, unvented indoor coal burning is strongly associated with increased risk of lung cancer and chronic obstructive pulmonary disease. However, the impact of coal burning and stove improvement on risk of pneumonia is not clear.MethodsWe conducted a retrospective cohort study among all farmers born 1917 through 1951 and living in Xuanwei as of 1 January 1976. The analysis included a total of 42,422 cohort members. Follow-up identified all deaths in the cohort from 1976 through 1996. Ages at entry into and at exit from follow-up ranged from 24 to 59 years and from 25 to 80 years, respectively. The record search detected 225 deaths from pneumonia, and 32,332 (76%) were alive as of 31 December 1996. We constructed multivariable Cox models (time variable = age) to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).ResultsUse of coal, especially smokeless coal, was positively associated with pneumonia mortality. Annual tonnage and lifetime duration of smoky and smokeless coal use were positively associated with pneumonia mortality. Stove improvement was associated with a 50% reduction in pneumonia deaths (smoky coal users: HR, 0.521; 95% CI, 0.340–0.798; smokeless coal users: HR, 0.449; 95% CI, 0.215–0.937).ConclusionsOur analysis is the first to suggest that indoor air pollution from unvented coal burning is an important risk factor for pneumonia death in adults and that improving ventilation by installing a chimney is an effective measure to decrease it.

Variation in lung cancer risk by smoky coal subtype in Xuanwei, China

Lung cancer rates in Xuanwei County have been among the highest in China for both males and females and have been causally associated with exposure to indoor smoky (bituminous) coal emissions that contain very high levels of polycyclic aromatic hydrocarbons. There are numerous coal mines across the County. Although lung cancer risk is strongly associated with the use of smoky coal as a whole, variation in risk by smoky coal subtype has not been characterized as yet. We conducted a population-based case-control study of 498 lung cancer cases and 498 controls, individually matched to case subjects on age (+/-2 years) and sex to examine risk by coal subtype. Odds ratios (ORs) and 95% confidence intervals (CIs) for coal subtype were calculated by conditional logistic regression, adjusting for potential confounders. Overall, smoky coal use was positively and statistically significantly associated with lung cancer risk, when compared with the use of smokeless coal or wood (OR = 7.7, 95% CI = 4.5-13.3). Furthermore, there was a marked heterogeneity in risk estimates for specific subtypes of smoky coal (test for heterogeneity: p = 5.17 x 10(-10)). Estimates were highest for coal of the Laibin (OR = 24.8, 95% CI = 12.4-49.6) and Longtan (OR = 11.6, 95% CI = 5.0-27.2) coal types and lower for coal from other subtypes. These findings strongly suggest that in Xuanwei and elsewhere, the carcinogenic potential of coal combustion products can exhibit substantial local variation by specific coal source.

Smokeless coal with high-heat value

Smokeless coal with high-heat value

Determination of PAHs in Combustion-Related Samples and in SRM 1597, Complex Mixture of PAHs from Coal Tar

Three types of combustion sample extracts, smokeless coal, smoky coal, and wood, were analyzed for a range of polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASH). Standard Reference Material (SRM) 1597, Complex Mixture of PAHs from Coal Tar, was also analyzed as a control sample and for the determination of a larger number of PAHs relative to those determined previously. Target analytes included many alkyl-substituted PAHs such as dimethylphenanthrenes, methylfluoranthenes, and methylpyrenes. The analytical methods included sample clean-up and the selection of specific stationary phases to accomplish unique separations of PAHs. Clean-up involved the use of normal-phase liquid chromatographic isolation of PAHs based on the number of aromatic carbons and a total PAH fraction, PAHs in the resulting fractions were separated by gas chromatography using two stationary phases with different selectivities and analyzed using mass spectrometry. These methods are discussed below and results are presented with an emphasis on the relative concentrations and distribution of PAHs in the combustion samples.

Chemical characterization of indoor air of homes from communes in Xuan Wei, China, with high lung cancer mortality rate

In a rural county, Xuan Wei, China, the lung cancer mortality rate is among China's highest, especially in women. This mortality rate is more associated with indoor air burning of smoky coal, as opposed to smokeless coal or wood, for cooking and heating under unvented conditions. Homes using different fuels from communes with high and low lung cancer mortality rates were sampled for particulate matter (< 10 μm) and semivolatile organics. The fine particles obtained from homes using smoky coal contained highest concentrations of organic matter (> 70%), including PAH, followed by homes using wood and smokeless coal. The major components present in the smoky coal filter samples were PAH and alkylated PAH. The smokeless coal filter samples exhibited profiles which were similar to the smoky coal samples except that some sulfur compounds were found. The estimated concentration levels of PAH in the smokeless coal samples were about one to two orders of magnitude lower than those of the smoky coal samples. In addition to PAH, aliphatic compounds and fatty acids were the major components found in the wood samples. Selected sample extracts from homes using smoky coal were fractionated into four fractions, and the results showed that the PAH and polar fractions have high mutagenic activity. Chemical characterization of the PAH fraction indicated that concentrations of some alkylated PAH were higher than those of their parent compounds. Chemical characterization of the polar fractions showed that nitrogen heterocyclic compounds are present.

Mouse skin tumorigenicity studies of indoor coal and wood combustion emissions from homes of residents in Xuan Wei, China with high lung cancer mortality

The rural Xuan Wei County, Yunnan Province, China, has an unusually high lung cancer mortality rate that cannot be attributed to tobacco smoke or occupational exposure. The lung cancer rate is associated with 'smoky' coal, in contrast to wood or 'smokeless' coal burned in unventilated homes. This study was conducted to characterize and compare mouse skin tumorigenicity of the coal and the wood combustion emissions and to link the animal data to human lung cancer. Indoor air particles (less than 10 microns) were collected from a central commune where the lung cancer mortality rate is high and smoky coal is the major fuel used and also from a south-western commune where lung cancer mortality rate is low and where wood or smokeless coal are the major fuels used. The organic extracts of these indoor air particles from smoky coal, smokeless coal and wood combustion were analysed for polycyclic aromatic hydrocarbons and assayed for skin tumor initiation activity and complete carcinogenicity in SENCAR mice. The results showed that the organic extract of the emission particles from smoky coal combustion is the most active in tumor initiation among the three combustion emission samples followed by smokeless coal and then wood. The organic extract of the particles from smoky coal combustion was shown to be a potent complete carcinogen, whereas the wood extract was relatively inactive as a complete carcinogen. The extract of particles from the smokeless coal combustion was not tested for complete carcinogenicity because of inadequate supply. Eighty-eight percent of the mice treated with the smoky coal extract showed carcinomas, averaging 1.1 carcinomas per tumor-bearing mouse at the end of the 77 week study. These findings were in agreement with the epidemiological data, which showed that the Xuan Wei residents using smoky coal as a major fuel in homes had a high lung cancer mortality rate. This study demonstrates that the results of the tumorigenicity assays in mice were in agreement with human lung cancer data.

焼結鋼に添加する炭素原料粉について

Effects of several types of carbon and graphite powders on the compressibility, sinterbility and carburization of the iron-carbon compacts were investigated by studying microstructures, and further mechanical properties of these sintered materials were determined. Carbon powders used in the present study were amorphous carbon such as coals, cokes and carbon blacks together with natural, artificial and kish graphites.Addition of amorphous carbon powders to iron powder generally led to lower compressibility and carburization than that of graphites. However, material using petroleum coak (green) powder showed good carburization and strength near to those produced using natural graphite powder, and material using kish graphite powder (particle size: 10μm) showed the most superior properties. In conclusion, the refining of carbon or graphite particles improved the properties of sintered materials. This was effective even for the amorphous carbon powders such as smokeless coal and petroleum coke which were usually considered to be poorly reactive.It was concluded that required properties for the additive carbon powder were high degree of graphi-tization, flaky shape and fine particle size about 10μm.