Coal Age

APR 2013

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black lung Researchers Believe Calcite Holds Promise as a Possible Deterrent for Black Lung Rock dust, or a concentrated form of it, may someday be used to offset the iron particles believed to cause coal workers' pneumoconiosis BY XI HUANG, YI LUO, ZENGLI ZHANG, SHUNING DONG AND KRAY LUXBACHER Recent epidemiological studies have indicated that prevalence of coal workers' pneumoconiosis (CWP) has increased in eastern Appalachian coals but not in other coal mine regions. Numerous toxicological studies have shown that bioavailable iron and quartz in the Appalachian coals are likely causative compounds that lead to CWP development. In the Western coals, calcite (CaCO3) prevents iron from becoming bioavailable and limits endogenous iron to interact with quartz, resulting in reduced toxicity of the coal dust. Here we propose a novel strategy to use calcite as a protective agent to prevent CWP in the Appalachian coalfield. This strategy may be more feasible than simply reducing dust concentrations, since the conventional dust control technology appears to have approached their maximum capacity, making an even more stringent dust standard impractical. Coal provides a dependable, inexpensive and long-lasting energy source worldwide. However, the subsequent health and environmental costs, such as coal workers' pneumoconiosis (CWP) or black lung disease, can increase the total cost by 60%100%. Hence, reducing CWP occurrence could financially benefit the society and the coal industry, not to mention mitigating the immeasurable costs exacted from coal miners and their families. The CWP disease, commonly associated with underground coal production, is one of the most common occupational diseases in the 20th century. The passage of the Mine Health and Safety Act in 1969 resulted in significant reduction of occupational exposures to coal dust and decreased CWP disease incidence. However, in developing countries, owing to the economy development, numerous miners are exposed to the coal mine dust. It is reported that there are more than 6 million underground coal miners in China and the number of new CWP patients is above 4,000 cases per year. Even in the United States, despite a slight decrease in CWP prevalence in the Western coal mine regions, the prevalence 54 www.coalage.com Figure 1: Injection of calcite before mining as a preventive agent for CWP through advanced drilling techniques. of CWP has increased markedly in Appalachia, such as Kentucky, Virginia and West Virginia coal mine regions since year 2000. Improved ventilation, the use of water sprays to wet and to capture airborne dust, and the improved cutting tool designed to generate less dust are the current strategies for the reduction of coal dust in underground coal mines. While efforts to limit underground coal workers exposure to coal mine dust must continue, these strategies appear to have approached their maximum capacity, making an even more stringent dust standard impractical (e.g., from 2 mg/m3 to 1 mg/m3 as has been proposed). This Appalachian region-specific increase in CWP calls for new research to develop a novel strategy that is beyond the conventional dust control technologies currently employed in the coal industry. Based on knowledge acquired through physico-chemical, toxicological and epidemiological studies on coals, here we propose a feasible approach to use calcite to reduce coal dust toxicity rather than reduce coal dust concentration. A fossil fuel, coal is an aggregate of heterogeneous substances composed of organic and inorganic materials (Meyers 1982). Among all known risk components in the mixed coal dust, coal rank or carbon-centered free radicals do not seem to play a significant role in CWP development. It appears to be bioavailable iron (BAI) and quartz that play major roles in coal dust-induced pathogenesis. It has been shown that, despite higher levels of respirable coal dust in Australian underground coal mines, lower respirable quartz content in the dust may contribute to the lower incidence of CWP in Australian coal workers as compared to their U.S. counterparts. A positive association was shown between CWP and quartz content with a correlation coefficient r=0.68, p<0.05. Studies on coals from the U.S. and EU have demonstrated a more robust association between BAI and CWP prevalence. For example, CWP prevalence in seven U.S. coal mine regions correlates with BAI levels in the coals with a correlation coefficient r=0.94, p<0.0015. Biological studies also indicate April 2013

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