What’s worse, inhaling or ingesting Mercury?
Inhalation= higher exposure
Where is mercury found?
- In soil and atmosphere from volcanic emissions
- Extracted and used in industry, enters air or water from pollution.
- Used to be used in some medications
Cause of occupational exposure of mercury
Gold mining
Methylmercury
- Most toxic form of mercury.
- Well absorbed when ingested.
- Very long half life.
What happened in Minamata, Japan?
- Outbreak of disease in fishing villages.
- Production at coastal factory used mercuric oxide as a catalyst.
- Affected 2,000.
Effects of Minamata disease in Infants
- Mental retardation
- Abnormal reflexes
- Cerebral palsy
- Developmental delays
Effects of Minamata disease in Adults
- Tingling, pricking sensation, numbness
- Tremors, convulsions
- Loss of sight, loss of smell, loss of hearing
- Dysarthria- speech disorder
- Cognitive impairments: loss of intelligence, excitement, hallucinosis
- Dizziness, insomnia
How do we go from mercury to methyl mercury?
biotransformation
Iraq mercury poisoning
- Mercury compounds used as anti fungal agent in seed grains.
- Made bread from treated seed grains.
Neurobehavioral Effects of Iraq mercury poisoning
- Blindness, deafness
- Cerebral palsy, seizures
- Abnormal reflexes & muscle tone
- Visual and auditory deficits
- Motor development delays
Effects on Brain (Iraq mercury poisoning)
- Decrease in brain size
- Cell loss
- Disorganization of cells
- Cell migration failures
Sources of Exposure to Methylmercury
- Biotransformed from normal mercury, then the bacteria are eaten by mollusks, etc.
- Poorly eliminated so goes to top of food chain- biggest and oldest predators.
- Methylmercury distributed evenly in fish and not affected by cooking.
Environmental Sources of Mercury
- Natural degassing of Earth
- Combustion of fossil fuel
- Industrial discharges and wastes
- Incinerations & Crematories
- Dental amalgams
Man Made Mercury Emissions per year (tonnes/year)
2,300
What caused Mercury pollution in the Amazon? What were the effects?
- After gold mining
- Mercury goes into water and air.
Effects - Altered altered vision in children of Brazil.
What percentage of mercury is released into the environment related to human activities?
50-70%
The Grasshopper Effect/ Global Distillation
Air carrying contaminants from the north settles at mid-lattitudes and then eventually goes to polar regions.
Another source of mercury in food
tuna
Chippewa Indians Study
- Recorded fish intake.
- Recorded blood mercury levels.
- Questionnaire
Results
- Most fish consumed in April/May
- Mercury levels in Chippewa related to fish consumption.
- Mercury levels are below those of known health effects.
What type of studies were used to determine “how much mercury is toxic”?
two large, prospective cohort studies
Study: “How much mercury is toxic?”
- Prospective cohort study
- Assessed mother/infant levels of mercury in blood and hair.
Results - No adverse neurological effects on offspring related to mercury exposure!
Faroe Islands mercury study & results
- Potential exposure to PCB’s from whale meat
- Adverse outcomes on tests correlated with degree of mercury exposure.
- Abnormalities in newborns correlated with high maternal mercury levels.
Suggested Reference Dose of Mercury per day
0.1 micrograms/kg/day
MeHg Consumption Limits
EPA: 0.1 micrograms/kg/day
FDA: 0/5 micrograms/kg/day
