small dose of mercury a small dose of toxicology a small dose of hg an introduction to the health...
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Small Dose of Mercury A Small Dose of Toxicology
A Small Dose of Hg
An Introduction To The Health Effects & Risk of
Mercury ExposureENV H 472 A - ENVIRONMENTAL
RISK AND SOCIETYClass 4
A Small Dose of Toxicology Small Dose of Mercury
Child Health
A Small Dose of Toxicology Small Dose of Mercury
Key Words of Toxicology
Hazard + Exposure = Risk
Individual Susceptibility
Dose / Response
A Small Dose of Toxicology Small Dose of Mercury
Mercury the Metal
A Small Dose of Toxicology Small Dose of Mercury
Methyl Mercury (MeHg)
Hg
CH3
A Small Dose of Toxicology Small Dose of Mercury
Hg - Inorganic & Organic
Hg
CH3
Inorganic – Quick Silver
Hg
Organic – Methyl Mercury
A Small Dose of Toxicology Small Dose of Mercury
Hg Facts & Uses
• Quicksilver• 13.6 times the weight of water• Evaporates at room temperature• Bacteria change to Methylmercury• Amalgam• Many Industrial uses
(thermometers, chemical reactions, gold mining)
A Small Dose of Toxicology Small Dose of Mercury
Hg – Like Water
A Small Dose of Toxicology Small Dose of Mercury
Hg – Solid Enough to Sit On
A Small Dose of Toxicology Small Dose of Mercury
• Alchemy• Medicine - cure syphilis?• Egyptian tomb -1500 BC
Ancient Awareness
A Small Dose of Toxicology Small Dose of Mercury
Greek God Mercury
“For then she bare a son, of many shifts, blandly cunning, a robber, a cattle driver, a bringer of dreams, a
watcher by night, a thief at the gates, one who was soon to show forth
wonderful deeds among the deathless gods...”
Description of the birth of the Greek God Mercury
A Small Dose of Toxicology Small Dose of Mercury
Occupational ExposureGold mining.
Hatters in the felt industry.
Historical Events
A Small Dose of Toxicology Small Dose of Mercury
Historical Awareness
A Small Dose of Toxicology Small Dose of Mercury Polluting with HG
Discharge in Minamata Bay
A Small Dose of Toxicology Small Dose of Mercury
Fetal Effects of MeHg
A Small Dose of Toxicology Small Dose of Mercury
Life-Long Effects of MeHg
A Small Dose of Toxicology Small Dose of Mercury
Planting Seed with Mercury
A Small Dose of Toxicology Small Dose of Mercury
Iraq Mothers with Bread
A Small Dose of Toxicology Small Dose of Mercury
Iraq Infant - Effects of Mercury
A Small Dose of Toxicology Small Dose of Mercury
Coal Fired Plants – Hg Emissions
A Small Dose of Toxicology Small Dose of Mercury
Outbreaks of MeHg Poisoning
Place Year CasesMinamata 1953-60 1000
Nigata 1964-65 646
Guatemala 1963-65 45
Ghana 1967 144
Pakistan 1969 100
Iraq 1956 100
Iraq 1960 1,002
Iraq 1971 40,000
On-going 2001 ???
A Small Dose of Toxicology Small Dose of Mercury
Inorganic - elemental mercury vapor Hg0
Inorganic - elemental mercury vapor Hg0
Biotransformation
Organic - Methylmercury - CH3Hg+
Bioaccumulation
Mercury to Methyl Mercury
A Small Dose of Toxicology Small Dose of Mercury
Mercury Release
50-75% mercury of released in the environment related to human activities
A Small Dose of Toxicology Small Dose of Mercury
Atmospheric Hg
A Small Dose of Toxicology Small Dose of Mercury
Ambient WaterSediments
Edible Fish
Inorganic Mercury
Methyl-Mercury
Methyl-MercuryIn Humans
Biomethylation
Bioaccumulation
Exposure
Discharge
Biotransformation of Mercury
A Small Dose of Toxicology Small Dose of Mercury
• Natural Degassing of the earth• Combustion of fossil fuel• Industrial Discharges and Wastes• Incineration & Crematories• Dental amalgams
Hg0 Hg2+ CH3Hg+
Environmental Sources of Mercury
A Small Dose of Toxicology Small Dose of Mercury
The Mercury Cycle
A Small Dose of Toxicology Small Dose of Mercury
• Blindness - Deafness• Cerebral Palsy - Seizures• Abnormal reflexes & muscle tone• Retarded motor development• Visual and Auditory Deficits• Delayed motor development• Altered DRH performance
Neurobehavioral Effects
A Small Dose of Toxicology Small Dose of Mercury
• Decrease in Brain Size• Cell loss• Disorganization of cells• Cell migration failures
Effects On The Brain
A Small Dose of Toxicology Small Dose of Mercury
How do you know?How good is the data?
Uncertainty
A Small Dose of Toxicology Small Dose of Mercury
Use of Uncertainty Factors
Divide Dose by Power of 10• Human variability• Interspecies extrapolation• Children• Subchronic to chronic extrapolation• Absence of a NOAEL• Database uncertainty
A Small Dose of Toxicology Small Dose of Mercury
Use of Uncertainty Factors
Animal Dose Response Data
NOAEL (No Observed Adverse Effect Level)
Divide by 10
(Account for inadequate animal data)
Divide by 10
(Animal to Human Extrapolation)
Divide by 10
(Human Variability or Individual Sensitivity)
Reference Dose (RfD) Or Acceptable Daily Intake (ADI)
A Small Dose of Toxicology Small Dose of Mercury
Reducing Uncertainty
• Upstanding mechanism of action• Physiologically based
pharmacokinetic models (distribution and metabolism)
• Sample size
A Small Dose of Toxicology Small Dose of Mercury
MONKEY - 25 µg/kg - LOAELRAT - 10 µg/kg - LOAELRAT - 50 µg/kg - replicated
Animal - Risk Assessment
A Small Dose of Toxicology Small Dose of Mercury
2.5 µg/kg - NOAEL (animals) 0.25 µg/kg - Human 0.025 µg/kg - Sensitive populations
Animal - Risk Assessment
(the rule of dividing by 10)
A Small Dose of Toxicology Small Dose of Mercury
• 10-20 ppm hair - LOAEL •• 40-80 ppb blood - LOAEL •
• 0.645 µg/kg •• 0.06 µg/kg - RfD •
Human - Risk Assessment
A Small Dose of Toxicology Small Dose of Mercury
Mercury Fishing Advisories
In 2000, 41 States have over 2000 fish consumption advisories
An increase form 27 in 1993 Pregnant women, nursing
mothers, women who intend to have children, and children under 15
A Small Dose of Toxicology Small Dose of Mercury
• Reduce environmental release
• Restrict global production and sale
• Advise women of child bearing age
• Research mechanisms of action
• Assess neurodegenerative effects
Recommendations
A Small Dose of Toxicology Small Dose of Mercury
MeHg Consumption Limits
US EPA – 0.1 ug/kg-day
US FDA – 1 ppm (mg/kg) in tuna
A Small Dose of Toxicology Small Dose of Mercury
Limit the amount of canned tuna you
eat, based on your bodyweight. Guidelines are: Women of childbearing age should limit the amount
of canned tuna they eat to about one can per week (six ounces.) A
woman who weighs less than 135 pounds should eat less than one
can of tuna per week. Children under six should eat less than one
half a can of tuna (three ounces) per week. Specific weekly limits for
children under six range from one ounce for a twenty pound child,
to three ounces for a child weighing about sixty pounds.
WA State Advisory
http://www.doh.wa.gov/fish/FishAdvMercury.htm
A Small Dose of Toxicology Small Dose of Mercury
WA State Mercury Chemical Action Plan• Reduce Hg in fish
• Reduce Hg release into the environment
• 4-5 tons of Hg released in WA
• Educating consumers about Hg in home
WA State Hg CAP
http://www.ecy.wa.gov/biblio/0303001.html
http://www.ecy.wa.gov/programs/eap/pbt/mercuryplan.html
A Small Dose of Toxicology Small Dose of Mercury
U.S. EPA Produced
“First-Ever Rule to Reduce Mercury
Emissions from Power Plants”
• Last 15 years no drop in Hg emissions
from power plants
• Is Cap and Trade appropriate for a
demonstrated neurotoxic compound?
Hg CAP and Trade
A Small Dose of Toxicology Small Dose of Mercury
Mercury A Global Issue
Mercury distribution and exposure is a global problem
A Small Dose of Toxicology Small Dose of Mercury
Precautionary Principle
"When an activity raises threats of harm to the environment or human health, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically."
- Wingspread Statement on the Precautionary Principle, Jan. 1998
A Small Dose of Toxicology Small Dose of Mercury
Alice’s Adventures
“Everything’s got a moral, if you can only find it”
Lewis Carroll in Alice’s Adventures in Wonderland
A Small Dose of Toxicology Small Dose of Mercury
• Children have a right to a safe, fair and healthy environment
• Ethical Responsibility to share and use of knowledge
• Duty to promote health and well being of children
• Thoughtful public health advocate
Knowledge - Responsibility
Small Dose of Mercury A Small Dose of Toxicology
Mercury or Lead
Questions or Comments?
Small Dose of Mercury A Small Dose of Toxicology
Additional Information - Hg
Web Sites World Health Organization - global
prospective on mercury health effects. http://www.who.int/water_sanitation_health/GDWQ/Chemicals/mercuryfull.htm
US EPA - Main site on Mercury. http://www.epa.gov/mercury/
The Mercury Policy Project (MPP). - works to raise awareness about the threat of mercury contamination - http://www.mercurypolicy.org/
www.asmalldoseof.org
A Small Dose of Toxicology Small Dose of Mercury
Authorship Information
For Additional Information ContactSteven G. Gilbert, PhD, DABT
E-mail: [email protected]: www.asmalldoseof.org
This presentation is supplement to “A Small Dose of Toxicology”