Mercury Sources, types and disposition

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MercurySources, types and disposition

• 3 forms of Hg
• elemental (metallic) - toxic when inhaled
• sources
• natural degassing of earth's crust 25,000
  -150,000 tons/year
• anthropogenic inputs 10,000 tons/yr
• used in manufacture of chlorine and sodium
  hydroxide, paint preservative and in electronics,
  as well as a byproduct from smelting,
• released from burning fossil fuels and coal
• vapors from mercuric nitrate in hat felting
  earned nickname of "madhatters"
• not well absorbed in gi tract (0.01), so broken
  thermometers not a problem
• concentrates in kidney, CNS

From Klaassen et al., Chap. 19, Philp, Chap. 6
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MercuryDisposition

• inorganic salt (mercuric chloride)
• about 7 absorbed in gi tract
• concentrates in kidney
• organic mercury mostly methylmercury
• most lipophilic form
• produced from inorganic hg by methylating
  bacteria in aquatic ecosystems
• bioaccumulates in aquatic food chain
• gt90 absorbed in gi, can cross blood-brain
  barrier
• concentrates in brain
• all forms can cross placenta to fetus
• all forms excreted primarily via kidneys

From Klaassen et al., Chap. 19, Philp, Chap. 6
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Mercury in Fish
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MercuryToxicity

• elemental
• vapor absorbed across alveoli, into red blood
  cells and blood-brain barrier
• acute symptoms weakness, chills, vomiting,
  diarrhea, cough and chest tightening
• continued exposure inflammation of interstitial
  areas of lung (interstitial pneumonitis)
• chronic exposure CNS effects - tremors and
  behavioral changes such as depression, shyness,
  confusion and forgetfulness
• inorganic salts
• precipitates out proteins of mucous membranes,
  leaving ash-grey color to pharynx and mouth
• causes mucous lining intestine to slough off can
  be accompanied by loss of fluids and blood
• leads to shock and hypovolemia
• acute necrosis of kidney tubules
• chronic damage to kidney glomerulus, "pink
  disease" (acrodynia) may be allergic based
• symptoms intense abdominal pain, vomiting

From Klaassen et al., Chap. 19, Philp, Chap. 6
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MercuryToxicity, continued

• organic mercury
• very high affinity for SH (sulfhydryl) groups
• binds to cysteine (sulfur containing amino acid),
  and then can substitute for methionine (an amino
  acid) and be incorporated into proteins
• can result in formation of abnormal microtubules,
  which are required for cell division and neuronal
  migration
• symptoms
• visual disturbances, weakness, uncoordination,
  loss of sensation/hearing, joint pain muscle
  deterioration, tremor, paralysis and death
• infants exposed in utero may be deformed and/or
  retarded

From Klaassen et al., Chap. 19, Philp, Chap. 6
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Detection and Treatment

• What would make you suggest Hg testing in a
  patient?
• How could you verify exposure?
• What treatments could you use?

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MercuryEpidemics

• Minimata Bay, Japan (1953)
• a manufacturing plant producing acetaldehyde
  discharged methylmercuric chloride into the bay
• mean conc. in fish was 10x higher than FDA limit
• 900 cases of "Minimata" disease among those who
  ate clams, mussels, and large fish from the bay
• 90 fatalities and many deformed/retarded infants

From Klaassen et al., Chap. 19, Philp, Chap. 6
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MercuryEpidemics

• Iraq (1972)
• methylmercuric Hg used as fungicide in seed
  coating on wheat
• wheat seeds were used to make bread instead of
  planted
• 6500 poisonings, 500 fatalities and many
  deformed/retarded infants (cerebral palsy)

From Klaassen et al., Chap. 19, Philp, Chap. 6
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MercuryEpidemics, continued

• English-Wabigoon river system, Canada (1969)
• levels as high as Minimata Bay from releases from
  paper mills and chloralkali plants
• .
• Sunken ship recovery (1810)
• HMS Trimuph salvaged 130 tons of Hg from a
  Spanish vessel pouches became damp and rotten,
  allowing Hg to vaporize
• 200 men affected within 3 weeks (5 fatalities)
• weakness, tremor, partial paralysis, mouth
  ulcerations

From Klaassen et al., Chap. 19, Philp, Chap. 6
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MercuryEpidemics, continued

• Cree Nation (native Americans of northern Quebec)
  - current
• Cree protesting plan of Hydro-Quebec to build
  large dam by diverting three rivers
• have lived in area for 5000 years
• expansion of this (LaGrande) project - 10,000 km2
  already flooded
• Hydro-Quebec has more power than current demand
  (no market for additional power)
• unless they sell it to US...
• most Cree have Hg levels that exceed WHO
  standard, some by 10x

From Klaassen et al., Chap. 19, Philp, Chap. 6
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Gold Rush Legacy

• 26 million pounds of elemental mercury were used
  by the gold mining industry between 1850 and 1900
• Hg used as metallic fly paper
• gold miners in California lost about 12.8 million
  pounds of mercury enough to fill more than 11.5
  billion household thermometers, 80 to 90 percent
  of it in the Sierra Nevada. Most of it is still
  out there.

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MercuryEpidemics, continued

• Amazon basin, Brazil
• Hg used to displace gold and silver in mining
  practices
• riverside communities have 15x higher hair Hg
  levels than recommended by WHO (100s of
  kilometers downstream from gold mines)
• symptoms are headaches, dizziness, numbness
  fatigue

NPR Story Guatemala
From Klaassen et al., Chap. 19, Philp, Chap. 6
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MercuryEpidemics, continued

• Quicksilver mess (1998 - Texarkana, AR)
• two teens found 40 lbs. of pure Hg in a factory
  that made neon lights
• 170 people exposed
• 6 people were hospitalized

From Klaassen et al., Chap. 19, Philp, Chap. 6
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Mercury in vaccines

From Klaassen et al., Chap. 19, Philp, Chap. 6