The integrated model developed for this assessment investigated the response time of fish mercury levels as an indicator of ecosystem recovery from changes in mercury emissions. Canada has been successful at conducting research and monitoring on the environmental and health processes of mercury over the past decades; however, many unknowns remain. In 2010, Alberta and Ontario equally shared nearly half of the national burden of mercury emissions. This chapter presents knowledge of mercury exposure of Canadians, studies of human health effects, and measures for risk management. Each chapter in the assessment discusses a different contribution to the overall mercury cycle and is identified in the drawing. Evers, D.C., 2005. These effects have been investigated as part of a unique long-term mercury study, Mercury Experiment to Assess Atmospheric Loadings in Canada and the United States (METAALICUS), conducted at the Experimental Lakes AreaNote de bas de page9 (ELA) in Ontario. The red dashed line levels off around 30 ug/m2/yr by 2010. In 2010, overall Canadian emissions of mercury were reported to have decreased by 85% in air and by about 50% in water since 1990. The Mercury Science Program, part of the Clean Air Regulatory Agenda (CARA), was developed in 2007 to establish the scientific knowledge base to support regulatory decision-making for mercury. At this time (2014), 4 sites in Canada collect these measurements: Alert, St. Anicet, Kejimkujik, Halifax, and the oil sands region (see Figure 13a). It drops to 0.21 mg g-1 wet muscle by 2030 and stays relatively constant to 2156. Mercury concentrations in wildlife may be affected by small-scale, local drivers (such as the introduction of zebra mussels into the Great Lakes), large-scale climatic drivers (perhaps related to the Pacific Decadal, Atlantic or Arctic Oscillations) or complex interactions of both. Overall impacts of climate change and land-use changes on the mercury cycle remain uncertain, There remains a lack of adequate, long term, coordinated, integrated and dedicated monitoring of mercury in Canada for air, water and biota, An increase in detailed information on reported emissions to the National Pollutant Release Inventory is required, There is a shortage of knowledge on emissions of mercury from surfaces and the impact of these emissions and re-emissions on Canadian inventories, There is a lack of understanding of the factors affecting methyl mercury production and promotion into aquatic food webs in Canadian ecosystems, Mercury dynamics in the terrestrial ecosystem represent the highest uncertainty in Canadian ecosystems, Characterization of atmospheric mercury species and their deposition remains unknown; this continues to limit predictive capabilities of current models, The number of exposure studies of mercury needs to be increased in infants and children less than 6 years of age, particularly for First Nations infants, There is a lack of information on the relationship between methyl mercury exposure and cardiovascular and renal diseases, and immunologic and carcinogenic effects, An effective nationally coordinated mercury monitoring program for sampling key indicators should be initiated, Integrated ecosystem research on mercury needs to be coordinated and conducted, A more detailed evaluation of the impacts of climate and land-use changes on the cycling and uptake of mercury is required, Detailed process research on deposition, terrestrial and ocean cycling, methylation and surface emissions should be prioritized, A comprehensive evaluation of the mercury emissions reported to the NPRI is required, Continued biomonitoring and follow-up studies to monitor trends of methyl mercury exposure is recommended, especially for vulnerable populations, Emphasis on proper communication of the risks of mercury exposure and the nutritional and socioeconomic benefits of fish and traditional wildlife food consumption should be made. However, for specific groups of people, including children (under 19 years of age), pregnant women, and women of childbearing age (younger than 50 years), a lower provisional mercury blood guidance value of 8 µg L-1 has been proposed by Health Canada in order to account for the increased susceptibility of neurological development of young children and fetuses. Releases to air and water in Canada have decreased from 1990 to 2010 by 85% for air and about 50% for water. Mercury pollution from point sources such as smelters and mining is not currently a significant problem for marine regions in Canada; however, there have been significant local impacts on Canadian marine areas during the 20th century. This chapter summarizes how mercury deposited from the air accumulates in undisturbed forested areas, using a recent case study. Mercury levels in stream and lake sediments vary across Canada by region and from one location to another. Figure 1 shows simple diagrams of the bioaccumulation and biomagnification processes. Chapter 10: “Mercury in Terrestrial and Aquatic Biota Across Canada: Geographic Variation” and Chapter 11: “Mercury in Terrestrial and Aquatic Biota Across Canada: Temporal Variation” are both shown on the land surface. and mercury accumulation in biota? Figure 2: The main processes that mercury undergoes in the ecosystem. The dashed lines represent the levels of mercury predicted for these two lakes when no additional emissions controls are applied to the model. Overall, risks of abnormal behaviour in common loons due to mercury exposure are found in 36% of the 677 Canadian lakes studied, and risks of impaired loon reproduction due to mercury, in 10% of 195 lakes studied. The numbers correspond to chapters in the full science assessment and indicate where that particular aspect of the cycle is discussed. The concentration levels start at 0.9 mg g-1 dry weight in 1975, reach a maximum around 2004 at 1.35 mg g-1 dry weight, and level off around 1.1 from 2005-2010. These changes may have serious impacts on how mercury is methylated within the system and how it is taken up by biota. Historical and Projected Canadian Mercury Air Emissions Trends. In comparison, in eastern Canada the total contribution of the same emissions from East Asia (20 to 23%) is comparable to the total contribution from the US (15 to 22%). The bottom graph, labelled Northern Pike (700 mm), has a range of 0 to 5 mg/kg ww. Despite the decrease in domestic anthropogenic emissions of mercury, the concentrations of mercury in air and biota have not declined accordingly. Once deposited on plants, soil, or into bodies of water, mercury can either be transformed back to its elemental form and be released, or enter the ecosystem as oxidized or particle-bound mercury. Greater decreases are found in regions that have experienced large decreases in anthropogenic emissions such as urban areas, Flin Flon, Manitoba, and the Great Lakes region. Mercury levels in common loons were high enough to cause risks of abnormal behaviour and of impaired reproduction in 36% and 10% of the Canadian lakes studied, respectively. One chapter (9) uses the information on processes from most chapters to tie together cycling of mercury in the whole ecosystem. Considerable research, monitoring, and modelling have been conducted to understand atmospheric processes affecting mercury in Canada. The number of years of data collected ranges from 5 to 17 years, with a minimum of no decline over 7 years (Genessee, AB), and a maximum of 34% over 11 years (Kuujjuarapik, QP). An effective national mercury monitoring program could make use of existing programs for mercury monitoring and for sampling biota for other purposes (other contaminants, biological indices, and health monitoring). Of the few soils studied in Canada, those in certain areas of Ontario and British Columbia have much higher emissions of mercury than study locations in the United States, Brazil, and Sweden. In the Arctic, levels of mercury remain high in some wildlife, and exposure to mercury through the consumption of traditional foods may pose health risks to northern Canadians. These long-term environmental changes influence mercury methylation processes, which affect the transfer and accumulation of mercury in biota. Speciation sites are at St. Anicet, Quebec; Alert, Nunavut; Kejimkujik and Halifax, Nova Scotia. If not, what factors are confounding/masking the expectation of recovery? a moose, goose, loon, fish, hiker and fisherman near the land/wetland area. UNEP, AMAP, 2013. Fish and wildlife populations that are at risk would likely benefit from further reductions in industrial mercury emissions, which would decrease the deposition of new mercury available for methylation and bioaccumulation. More acidic (lower pH) aquatic conditions generally lead to higher methylmercury levels in biota. Health effects, in particular neurological impairments, are associated with exposure to high levels of methylmercury. However, lakes will take years to centuries to fully respond to emissions reductions, depending on the characteristics of the catchment. Data on mercury concentrations in Canadian plants and animals have been collected for decades. Global and US emissions are larger than Canadian emissions, which make distinguishing between domestic and foreign impacts a challenge. The red dashed line stays at approximately 8 mg m-2 yr-1  from 2007 to 2156. In addition, mercury levels in species such as piscivorous fish, seabirds, and marine mammals can also be used as indicators of ecosystem recovery. While many of the direct emissions have decreased, revolatilization of historically deposited mercury can contribute to the continued elevated levels of mercury in the air. Figure 8: Relative contributions from emissions from individual source regions to net mercury deposition for the Canadian Arctic, British Columbia, Ontario and New Brunswick, Nova Scotia and Prince Edward Island combined for the year 2005 (as estimated by the Global/Regional Atmospheric Heavy Metals model). Figure 11 shows two graphs of predicted levels of mercury deposited from the atmosphere (red), the level of mercury loaded into the terrestrial ecosystem (green) and the levels of mercury in fish (blue) at two different lakes in Canada using mathematical modeling. Figure 4 is a map of Canada with a square over the Great Lakes region (enlarged to provide a more refined view of that area). The acidification of aquatic systems that lack properties to buffer acid is long-lasting and may continue for decades after acid emissions controls have been implemented. The bottom level consists of small green dots to depict plankton, which have a low mercury level (represented by the yellow arrow). Refining fossil fuels, burning coal, and metal smelting emit mercury and associated acid precursors, such as sulphur dioxide and nitrous oxides, to the air. It provides an in-depth knowledge baseline against which future changes in mercury levels in the environment can be attributed to changes in mercury emissions and climate. The top graph is labelled Lake Whitefish (400 mm) and has a y range of 0.0 to 0.6 mg/kg ww. Acid deposition from these sources leaches mercury from soils to aquatic systems and can cause an overall decrease in water pH. 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