Local Impacts of Mercury Emissions from Coal Fired Power Plants on Human Health Risk. Progress Report for the Period of March 2002 through March 2003

摘要

This report presents a follow-up to previous assessments of the health risks of mercury that BNL performed for the Department of Energy. Methylmercury is an organic form of mercury that has been implicated as the form of mercury that impacts human health. A comprehensive risk assessment report was prepared (Lipfert et al., 1994) that led to several journal articles and conference presentations (Lipfert et al. 1994, 1995, 1996). In 2001, a risk assessment of mercury exposure from fish consumption was performed for 3 regions of the U.S (Northeast, Southeast, and Midwest) identified by the EPA as regions of higher impact from coal emissions (Sullivan, 2001). The risk assessment addressed the effects of in utero exposure to children through consumption of fish by their mothers. Two population groups (general population and subsistence fishers) were considered. Three mercury levels were considered in the analysis, current conditions based on measured data, and hypothetical reductions in Hg levels due to a 50% and 90% reduction in mercury emissions from coal fired power plants. The findings of the analysis suggested that a 90% reduction in coal-fired emissions would lead to a small reduction in risk to the general population (population risk reduction on the order of 10(sup -5)) and that the population risk is born by less than 1% of the population (i.e. high end fish consumers). The study conducted in 2001 focused on the health impacts arising from regional deposition patterns as determined by measured data and modeling. Health impacts were assessed on a regional scale accounting for potential percent reductions in mercury emissions from coal. However, quantitative assessment of local deposition near actual power plants has not been attempted. Generic assessments have been performed, but these are not representative of any single power plant. In this study, general background information on the mercury cycle, mercury emissions from coal plants, and risk assessment are provided to provide the basis for examining the impacts of local deposition. A section that covers modeling of local deposition of mercury emitted from coal power plants follows. The code ISCST3 was used with mercury emissions data from two power plants and local meteorological conditions to assess local deposition. The deposition modeling results were used to estimate the potential increase in mercury deposition that could occur in the vicinity of the plant. Increased deposition was assumed to lead to a linearly proportional increase in mercury concentrations in fish in local water bodies. Fish are the major pathway for human health impacts and the potential for increased mercury exposure was evaluated and the risks of such exposure estimated. Based on the findings recommendations for future work and conclusions are provided.