Mercury, an extremely toxic metal, is an inexhaustible source of problems for living beings. Volatile, the element can contaminate aquatic and terrestrial ecosystems. Heavy, removing it from any location is an arduous task.
Present in the weakened Yanomami territory due to mining, which, in addition to spreading diseases, makes it impossible for indigenous peoples to use the soil and rivers for agriculture and fishing, the element spreads through the bloodstream of human beings, causing organ failure and complications in the central nervous system.
Rogério Machado, professor of chemistry and environment at Universidade Presbiteriana Mackenzie, says that the element is rarely used in the world, except for mining. “Mercury is not something natural in Brazil, there are no natural reserves [solo vulcânico] around here, the biggest ones are in Spain, which doesn’t even explore the element. So why does he come here? Simply for the sake of gold.”
The professor explains that the metal is important for hunting gold nuggets because both are neighbors on the periodic table. The difference is an electron — a particle present in the structure of the atom and which has a negative electrical charge. With this proximity, the fusion between both is facilitated.
This connection is called amalgam, a product resistant to oxidation.
This reaction is not exclusive to contact between gold and mercury. The latter forms the same substance with almost all other metals, with exceptions being iron and platinum.
In mining, the reaction that forms amalgam becomes very useful. When mercury is dropped on a rock with nuggets, the transformation is immediate. Mercury, at room temperature a silvery liquid, soon becomes matte, facilitating the search for gold.
When pieces of rock with golden spots are found, the prospector throws them into an iron bowl and, with a blowtorch, heats it up so that the mercury evaporates and the precious stones remain.
“Mercury doesn’t need much to evaporate, it’s just over 356°C. When it evaporates, that’s when the danger appears. The droplets fall into rivers and the surrounding soil, condemning all these spaces”, states Machado.
In its metallic state, mercury does not cause many problems to the human body, says the professor. The great difficulty is in the ingestion of fish and plants contaminated with the substance.
“When it falls into the water, it settles in the soil and is absorbed by plants. What does the plant do with this metal? the fish eat the plants and this enters the food chain”, says the professor.
Conrado Borges, a neurologist at Hospital Sírio-Libanês, says there are two types of mercury poisoning.
“The individual who has direct contact with the agent, like the prospector himself, is affected by acute intoxication when inhaling the steam. This causes inflammation of the lungs and swelling, in addition to problems in the digestive tract”, he explains.
The second type, called chronic poisoning, is caused by the continuous ingestion of contaminated food, such as fish and, less frequently, plants. It is from him that the most serious complications derive.
Through the bloodstream, mercury attacks the organs, especially the kidneys, which cannot filter it due to weight. In some cases, there is also muscle atrophy. Then it attacks the central nervous system.
“The initial diagnoses range from a mild headache to insomnia. Then there are very serious things, such as memory loss, cognitive impairment, anxiety, irritability, depression and dementia”, says Borges.
He claims to be difficult to treat intoxication. The solution, still according to Borges, would be to eliminate the source of intoxication, the contaminated fish and plants, and hope that there are no consequences.
More serious cases can also be treated with chelating, a substance that removes mercury from the body through urine. “The truth is that, anyway, there is never any certainty of improvement. And those people can still continue to consume the source of the problem. What will they eat in the future?”, questions the neurologist.
Thiago Mendes, a biologist specializing in animal behavior —an area that studies the interaction of beings, including humans, with other organisms and the physical environment—says that the biological system of the Yanomami land should take between 20 and 30 years to be rebalanced.
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