Transcript Document
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.
References:
1
Kathryn R. Mahaffey, Ph.D., “Methylmercury: Epidemiological Update,” USEPA, Washington D.C., Fish Forum, 2004: 5.
2
John Walke, David Hawkins, and Linda Greer, National Resources Defense Council, press release, 5 Dec. 2003.
3
National Research Council, “Toxicological Effects of Methylmercury,” (National Academy Press, Washington, DC, 2000), 4.
4
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9
10
11
12
13
Editorial, “Connect the Dots: What’s Shaping Mercury Rules?” Minneapolis Star Tribune, 18 Feb. 2004.
Klaassen, C.D., (ed), Casarett and Doull’s Toxicology. 5th ed., 1996, New York: McGraw-Hill.
Elizabeth Weise, “Mercury Damage Irreversible,” USA Today, 9 Feb. 2004: D6.
http://www.epa.gov/air/mercuryrule/basic.htm
Bill Becker, State and Territorial Air Pollution Program Administrators/Association of Local Air Pollution Control Officials, press release, 25 Feb. 2004.
Environmental Protection Agency, letter from Children’s Health Protection Advisory Committee to Michael Leavitt, 26 Jan. 2004.
US EPA Office of Water, Draft Mercury Deposition Modeling Results, 2003.
Tom Atkeson, Don Axelrad, Curtis Pollman, Gerald Keeler, “Integrating Atmospheric Mercury Deposition and Aquatic Cycling in the Florida Everglades,” Florida Department of Environmental
Protection,
October 2002, revised November 2003: ii,iii.
13
Hrabik, T.R., Watras, C.J., “Recent declines in mercury concentration in a freshwater fishery: isolating effects of de-acidification and decreased atmospheric mercury deposition in Little Rock Lake,”
Elsevier, The Science of the Total Environment, 297 (2002) 229-237.
14
National Wildlife Federation, “Mercury Deposition: Clean the Rain,” February 2004.