Presentation on theme: "Mercury Contamination on Tribal Lands Leech Lake Water Quality Program."— Presentation transcript:
Mercury Contamination on Tribal Lands Leech Lake Water Quality Program
Mercury Facts U.S. EPA estimates that more than 600,000 children each year may be exposed to dangerous levels of mercury in the womb In 2002 health departments in 44 states issued advisories warning the public to limit or avoid their consumption of locally caught fish 17 states have issued statewide warnings that cover every lake and stream These warnings cover 12 million acres of lakes and 473,00 miles of streams High mercury levels in fish affect Tribes in which fishing is a part of their subsistence lifestyle and cultural tradition
Mercury Basics -Mercury is naturally occurring element that is present throughout the environment. -It is one of the “transition metals” on the Periodic Chart of Elements. - Mercury also forms salts –mercury chloride (corrosive) -mercurous chloride (still used in medicine) -mercury fulminate (used in explosives) -mercuric sulfide (paint pigment) -Mercury enters the atmosphere from natural processes such as volcano eruptions, groundwater seepage and evaporation from the oceans as well as human activity. -The majority of exposure in the U.S. is from methylmercury in fish
Forms of Mercury Mercury in the environment shifts among forms Organic mercury compounds Ex.)Methylmercury Can enter the body readily through lungs, skin and stomach Form of Hg found in fish Elemental Hg Liquid at room temperature Gives of vapor that can be inhaled into lungs and passed into bloodstream. Inorganic mercury compounds Can be absorbed through stomach if swallowed, or inhaled Found mainly in as salts or in medicines and cosmetics
Where is the Hg coming from? Coal-fired utility boilers Hazardous waste combustors Chlorine production Industrial boilers Medical waste incinerators Municipal waste incinerators Plants in the midwest and Texas create the majority of Hg emissions
Mercury Transport Pathways Wet/dry deposition of particulate Hg Volatilization Reduction or oxidation Photodegradation Methylation Hg is transfromed by sulfur bacteria Need carbon as a food source for energy 10% of Hg available is converted Sulfur contaminated rain also largely contributes to increased methylation (fish 10x more contaminated since the industrial revolution) Demethylation
Mercury to methlymercury - Once released, mercury can be deposited onto soil and into water bodies. -Bacteria in sediments convert mercury to methylmercury. -Taken up by tiny plants and animals -Fish that eat these organisms build up methylmercury in their bodies -As bigger fish eat smaller ones, the methylmercury is concentrated further up the food chain -"bioaccumulation“ -Therefore, the primary route of uptake is through human consumption of contaminated fish
Methlymercury bioaccumulation Easily absorbed through gastrointestinal system Total body burden of mercury is vital Hg concentrations are higher in larger, older predatory fish Tuna, Atlantic mackerel, shark and swordfish In Minnesota, walleye and northern pike Shrimp, canned light tuna, salmon, pollock and catfish have lower Hg content
Methylmercury basics -Food types seems to make no difference in absorption; 95% of ingested MeHg is absorbed -MeHg is distributed throughout the body and easily passes the placenta and blood-brain barriers -Half-life of MeHg is approximately 70 days -Good biomarkers of exposure : Blood, hair and nails -Different forms of mercury may produce health effects in the same way (have a common mode of action)
Leech Lake Tribal lands Leech Lake Tribal lands contain 865,000 acres of water Wild rice grows abundantly and is harvested for subsistence by tribal members along with many species of fish. Each of these food sources is heavily impacted by Hg contamination and are widely used foods on the reservation In addition, other foods and medicinal sources may be equally affected.
The total measured annual Hg input for Leech lake is 7.67 pounds of which 87% was atmospheric loading. The total export is 1.25 pounds and annual Hg stored is 6.42 pounds Mercury in Leech Lake calculated avg. of 0.39 ppt, ranging from 0.22 to 0.94ppt. Mercury Loads to Leech Lake T=5.394qci Q=the avg. daily flow for the period C= the total Hg conc. of the water (mg/L) I= the # of days in the period Data taken from a water quality assessment of the Leech Lake Watershed July 1997 by the LLDRM and the MTC
Mercury consumption guidance Many state health agencies guidance for mercury concentrations in fish is 0.3- 0.5ppm (average American who consumes 5 lbs. of fish/yr.) Leech Lake Environmental Dept. and MCT utilize a subsistence threshold mercury fish tissue concentration consumption guideline of 0.02ppm based on consumption of 180 lbs./yr. (15lbs./month)
Mercury in fish from Leech Lake Ex) Mercury in Leech Lake Fish: Northern pike: 0.16 ug/g---1.9lbs. Fish Sucker: 0.26 ug/g---2 lbs. Fish Walleye: 0.26 ug/g---2lbs. Fish Muskie: 0.15 ug/g---1.9 lbs. fish Bluegill: 0.028 ug/g---0.2 lbs. fish Whitefish: 2.8 ug/g----2.8 lbs. fish Larger the fish, more mercury. Predatory fish higher Hg concentrations as well. Data taken from: Water quality assessment of the Leech Lake Watershed July 1997 by the LLDRM and the MTC
How are tribal lands more at risk? Subsistence lifestyles of tribes consume 40 times more fish and game than the average American. Many reservations within Minnesota and ceded territories which tribes hunt, fish and gather are located on or near wetlands where methylization is most likely to occur. When fishing tribes face consumption advisories, it is a hard decision to risk the health of the tribe or their tradition and cultural ways
Health effects from Hg Mercury is a well-known neurotoxin Shown to cause learning problems, memory loss, numbness, loss of muscle coordination, tremors, deafness and changes in vision Infants exposed to Hg in the womb are at risk for mental retardation, cerebral palsy and heart disease. Since fish, wild rice and game species are main food sources for tribes, it is unfortunate that the exposure to methylmercury is high.
Methylmercury Health Effects -Effects of exposure during development or to adults can cause mortality at very high levels -At lower doses, delayed responses, neurological effects, effects on tests related to ability to learn and process information may occur -Not likely to be a human carcinogen (Tumors are seen in animals only at extremely toxic doses; neurological effects are observed at lower exposures) -Developing nervous system is a sensitive target for low dose MeHg exposure -Human and animal evidence shows cardiovascular effects -Animal evidence shows immune and reproductive effects
How do tribes address the threat of mercury locally? There is a continuous effect to monitor, analyze and find areas of possible clean up of mercury contamination in and around their lands. Although, Mercury sampling is expensive and labor-intensive and not every tribe is funded to conduct research Public outreach to local tribes on the issues of mercury contamination For example, Fond du Lac Band of the Lake Superior Chippewa in MN have been monitoring Hg for 7 years. Sources in the area include coal-fired power plants within 150-200 miles, taconite plants that burn coal and some natural deposits. This tribe and many others in MN conduct mercury-deposition studies as well as fish-tissue and sediment sampling.
Local Tribal Studies Studies conducted at Fond du Lac Band of the Lake Superior Chippewa in MN have shown: Hg levels are most elevated in shallow bodies of standing water, particularly where organic sediment is highest A third of the reservation’s major lakes show high levels of Hg 3,600 pounds of Hg was released in MN in 2000, and all but a fraction have volatized into our atmosphere. Those emissions were responsible for 10-30% of the total deposition in the state In addition, wild rice has not shown an elevated level of Hg, but has shown an elevated level in waterfowl that ingest wild rice Mercury impacts on the reservation are not only health threats to tribal members, but also to the cultural focus and income source for the tribe.
Federal Regulatory Responses In 2000, Clinton administration had set new mercury control proposals based research to cut mercury emissions by 50% by 2005. Within months, Bush administration rescinded the Clinton proposals and replaced them with reducing emissions by 30% by 2010 and 70% by 2018. In addition the Bush administration, has proposed that mercury be market-traded. Bush has also allowed for upgrades of up to 30% of the facility’s worth with their having to install new pollution controls.
Conclusion -Ingested methylmercury represents the major mercury exposure for most people, especially for Native Americans -Health hazards of methylmercury vary with exposure level and are based largely on observations in humans. -Recent and continuing studies of U.S. populations help us to better understand who is exposed to and at what levels of methylmercury.
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