Rogerio Aparecido Machado
Professor of Chemistry and Environment at Mackenzie Presbyterian University
The current situation in the north of the country regarding mercury contamination and the consequent harmful effect on the indigenous population may seem to be emerging now, but in reality, both in our country and in other parts of the world, contamination by this metal is nothing new. , much less 21st century exclusivity.
Even before the 20th century, mercury was used for many applications and, until recently, we had it in dental treatment, in the case of dental fillings.
One of the questions that does not want to remain silent on the subject: Why is mercury so dangerous?
The answer could even be simple. This metal, unlike many others, has no function in the human body, and worse, it is extremely difficult to remove it from the human body, as it has high toxicity for our body.
When it enters the body, it lodges in vital organs such as the kidneys and liver, not to mention the central nervous system, where this metal acts in such a way that it takes away all human beings’ ability to control their movements and even reasoning, leading to death.
In fact, mercury itself, the metal that we know visually as a metallic liquid, when in contact with the skin or even in its occasional ingestion, it is almost not absorbed, only 0.1% can be absorbed, the majority is excreted in feces or urine.
The problem can start when the mercury passes to its ionic form, which can be absorbed in up to 20% by our organism. Plants can accumulate mercury in this form.
But, this is not the most lethal form. The most worrying form is what we call methylated, that is, when mercury combines with organic molecules and is in the form of methylmercury, a metallic organ. This organometallic form is absorbed up to 99% by our body.
However, the mercury used in mining is the metallic liquid, as mentioned, the least absorbed by humans; how then could the mercury in question be so dangerous?
In prospecting, when gold is discovered, it may be added to other minerals, such as rock, for example, and to separate the gold from the rock, the prospector throws metallic mercury into the rock, and the mercury will form an amalgam, a kind of alloy between gold and mercury, with gold being connected to mercury in liquid form.
Why does this happen, i.e. why does an amalgam form? Because the difference in the atomic structure of gold in relation to mercury is only one electron, this greatly facilitates the immediate formation of the liquid alloy (amalgam) and consequently the extraction of gold from where it is aggregated.
To separate this alloy and recover the gold, the prospector places the liquid alloy in a type of metallic dish and, with the aid of a torch, he burns the alloy, and the mercury with a boiling point lower than 400 degrees Celsius evaporates, thus remaining in the dish the molten gold with few impurities. This is a quick process.
The environmental problem/disaster: when mercury evaporates, the first to be contaminated is the torch operator who is close to the mercury that is evaporating, and he directly inhales the vapor, entering his bloodstream.
Evaporated mercury is carried by the air and deposited on plants and, as it is generally a river environment, most of the mercury falls into rivers.
This metallic mercury can be absorbed by plants in the rivers, turning into ionic mercury and, later, being food for fish, which absorb ionic mercury and transform it into methylmercury.
There is still a great possibility that the metallic mercury is absorbed by the fish in its breathing process, where it sucks in the contaminated water and, in turn, metabolizes the mercury in its organism.
The human being will become contaminated, mainly by eating contaminated fish, which have mercury in its methylated form, and will end up absorbing the mercury contained in the fish almost completely.
The contamination of the indigenous population has been going on for many years in this way, and because they are isolated, only now with the publicizing of the great deforestation to increase the mining area, as well as the clear contamination of Amazonian rivers, the population in general is beginning to know what drama experienced by Brazilian Indians.
We must not be under the illusion that it will be enough just to stop mining and everything will go back to what it was decades ago. Contamination of the soil, as well as the bottom of rivers, is time consuming and requires technology for its remediation.
This could be an error that Brazil has to live with for many decades, and unfortunately even for a century, as the contaminated sites are not easily accessible. However, the impression is that no one thinks about such a problem, only about the desired profit, costing what it will cost for years.
About Mackenzie Presbyterian University
Universidade Presbiteriana Mackenzie (UPM) ranks 71st among the best educational institutions in Latin America, according to the Times Higher Education 2021 survey, an international educational research organization, which evaluates the performance of secondary, higher and postgraduate education institutions. graduation.
Celebrating 70 years, UPM has three campuses in the state of São Paulo, in Higienópolis, Alphaville and Campinas. The courses offered by Mackenzie include Undergraduate, Graduate, Master’s and Doctorate, Graduate Specialization, Extension, EaD, In Company Courses and Center for Foreign Languages.
