Mercury pollution incidents around the world

Problem of environmental mercury pollution in the world

There are several possible sources of mercury pollution. Pollution caused by factory drain or organo-mercurial pesticide has been decreasing though it still continues to occur mainly in developing countries. On the contrary, mercury pollution caused by small-scale gold mining activities or mercury from closed mines, as well as mercury-polluted soil in the sites of demolished chemical factories has become serious recently.
It is urgent necessity to take measures for mercury pollution and to study its health effect in pollution-ridden areas. The National Institute for Minamata Disease has positively engaged with such activity.

Humanity has been destroying nature in order to put land to use. No small number of people believe that it is more "useful" for humans to manipulate it than to maintain it in its natural state. Is nature really useless for humans, though?
Forests produce oxygen, oceans adapt climate and tidelands purify water.　A certain researcher has calculated how much it would cost to have such "services" performed with artificial facilities instead of nature. Results: nature, on a global scale, is providing us with services worth over 3,500 trillion yen.
If we keep destroying nature, humanity would eventually have to spend money to do what nature has thus far been doing for us for free.

In the Amazon River basin in Brazil, placer mining boomed at the end of the 1970ʼ s; many people began mining riverbeds and the ground of tropical forests. Since miners used metallic mercury for refining placer ores, released mercury polluted the river and its basin. Similar mercury pollution problems occurred in Tanzania, the Philippines, Indonesia, China, and several other countries. To date, studies of these pollution problems have revealed that mercury released into rivers were converted to methylmercury, and accumulated in fish living in the rivers concerned. In addition to the inorganic mercury poisoning afflicting miners, therefore, methylmercury poisoning is likely to affect the health of residents in the relevant basins, particularly those living along the lower reaches of the rivers. To address such potential health problems, scientists of various nations visited polluted areas to jointly survey the degrees of pollution and its influence on the health of residents.

circulation of mercury released by gold(placer) miners in the Amazon River basin

Metallic mercury (Hg⁰) used for refining placer ores is released from minersʼ rafts into the river water. Of the amount, 55-60% evaporates, while the remaining 40-45% falls into the water. In the air, the evaporated Hg⁰ is oxidized by water (H²O) and ozone (O³), and becomes mercury ion (Hg²⁺), which then falls onto the ground with rain. If it falls on ground of acid soil (around pH4), Hg²⁺ transforms to organic methylmercury (Hg(CH³)⁺), which is the immediately taken in by organisms living in the soil. The methylmercury then undergoes bioaccumulation through the food web.