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Chemical Integrity

Introduction

Sources and Forms of Mercury

Mercury and Human Health

Mercury and Fish Consumption

Complications of Chemical Mixtures

Reductions in Mercury Emissions

Conclusions

Recommendations

Figures

 

Reductions in Mercury Emissions

The U.S. Environmental Protection Agency cites rough estimates showing that 20% of global mercury emissions are from natural emissions, 40% from global re-cycling of previous anthropogenic activity, and 40% from current anthropogenic25 emissions 26. As shown in Table 4, North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995.

Table 4 (Pacyna and Pacyna)27 ( click on table to enlarge )

Table 2 (Pacyna and Pacyna)

With their later industrialization, mercury emissions are now increasing in developing countries. Preliminary findings from U.S. Environmental Protection Agency and Environment Canada indicate that increases in global anthropogenic mercury emissions reaching North America, largely from Asia, offset anthropogenic mercury reductions achieved within the United States and Canada. In the 2001-2003 Great Lakes Priorities Report to the Commission, the findings of our International Air Quality Advisory Board on the transportation and deposition of mercury to each of the Great Lakes via the atmospheric pathway enlarge on these issues.28 With respect to Lake Superior, the lake most remote from regional industrial sources, the majority of specific sources of mercury deposition were located at a distance greater than 700 kilometres away. Although global emissions are largely of the unreactive form, the sheer volume and increasing proportion of these global mercury balance warrants attention.

Mercury emissions arising from human activity in both the United States and Canada dropped substantially between 1990 and 1999. In the United States, significant mercury reductions came principally from emission controls on municipal and medical waste incinerators, as well as improved screening and removal from the waste stream of commercial products such as batteries and paint. In Canada, significant reductions were achieved largely through controls and process alterations in the metal smelting industry, the near-complete closure of the chlor-alkali industry, and further control and restrictions on waste incineration. In 1999, U.S. mercury emissions were estimated as approximately 124 tonnes (137 tons); further detailed verification of these data now indicate total 1999 emissions were 105 tonnes (116 tons). Canadian mercury emissions were approximately 11 tonnes (12.1 tons). Coal-fired utilities account for approximately 35% and 27% of mercury emissions in the U.S. and Canada, respectively. (See Figures 4 and 5). 29

Figure 4 ( click on figure to enlarge )

Figure 4

Figure 5 ( click on figure to enlarge )

Figure 5

Governments in both countries are examining ways to reduce mercury emissions from coal-fired electrical generation facilities. The removal of mercury from coal is technologically challenging.

On December 17, 2003, the Environmental Protection Agency proposed significant reductions in sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions from power plants. Although the proposal targets these chief components of acid rain, it is anticipated that actions taken to meet those standards will result in "co-benefits" of reductions in mercury emissions and fine particulate matter. The U.S. Environmental Protection Agency has also proposed alternatives for ways to reduce mercury emissions from utilities. These alternatives include creating a market-based "cap and trade" program to reduce mercury emissions in a two-phased approach, and requiring utilities to install controls known as "maximum achievable control technologies" (MACT).

The Canadian Council of Ministers of the Environment has committed to develop a Canada-wide standard to reduce mercury emissions from the coal-fired electric power generation sector by 2010 (with variance in provincial application of the national target or standard), to explore the national capture of mercury from coal burned in the range of 60-90% (including all efforts to reduce mercury releases, from pollution prevention through emissions control), and to align with US standards for mercury. The standard will apply to existing and new plants.30 As well, Canada-wide standards for mercury-containing fluorescent lamps and dental amalgam waste will assist in meeting the Canada-Ontario Agreement commitment to reduce mercury releases by 90% by 2010. Jurisdictions are required to develop an implementation plan which describes what actions will be taken to implement a Canada-wide standard and achieve compliance by the deadline set for the standard, except that as Quebec is not a signatory to the Canada-wide Accord on Environmental Harmonization nor the Canada-wide Standards, it is not required to develop an implementation plan,31 however the principal mercury sources from Quebec are included in the National Pollutant Release Inventory.

With respect to the lower Great Lakes, information provided by the Commissionís International Air Quality Advisory Board in the 2001-2003 Priories Report shows that there are significant regional and local sources of mercury emissions. The Boardís report shows that 40% of the mercury emission from coal-fired generation facilities in that region is in the more biologically-available reactive form. The waters of the Great Lakes also continue to receive mercury from previously contaminated sediments. In addition, contaminated groundwater and wastewater discharges contribute to the local mercury burden, especially in Areas of Concern. Because the U.S. and Canadian governments can control emissions from sources within their jurisdictions more effectively than some global emissions, and because reactive gaseous mercury is more biologically available, governments should substantially reduce the deposition of reactive gaseous mercury in the Great Lakes region.

The combined impacts of mercury contamination in Canada are difficult to quantify, 32 and the exact proportion of the impact which can be ascribed to natural mercury and to past and present anthropogenic releases cannot presently be quantified. 33 The U.S. Environmental Protection Agency cited a plausible link between mercury from industrial combustion sources and methyl mercury in fish, but noted that it was not possible to quantify how much of the methyl mercury in fish consumed by the U.S. population is contributed by U.S. emissions relative to other sources of mercury (such as natural sources and re-emissions from the global pool).34 A recent study in the Florida Everglades estimated how quickly fish tissue levels respond to decreased regional mercury emissions. Reductions in total mercury emissions of approximately 90% since the late 1980's have been paralleled by a reduction in average fish tissue methyl mercury of about 80%. 35 However, more definitive information, ideally through studies focused on the Great Lakes, would be helpful in exploring linkages between mercury emissions and deposition, and biologic uptake and effects.