Important points for understanding
-As the MeHg occurs in nature, but its concentration is important factor. Only MeHg
exposure at high levels (heavy exposure) is the cause of the Minamata disease. And rate of
intake dose in fish-eating human body should be under control.
-The MeHg absorption in fish body does not cause effects to fish-itself, therefore even with
high intake, a fish still can survive. This causes danger easily to fish eating human
populations.
-River and Ocean/sea environments or ecosystems in are different respect with the MeHg.
In the case of the Minamata, at first the wastewater discharged to the river and during that
period due to some reasons the Minamata disease not arose sharply, I think: 1. a river is open
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dynamic aqua system, which could purify itself naturally; 2. Comparing with marine
ecosystem, a river has less microorganisms and salt/salinity (chloride) and as a result it was
less methylated. 3. Fishes of river accumulates lower biological concentration of MeHg than
carnivore fish and marine mammals.