Mercury is considered one of the most dangerous metals for human health and it is spreading throughout the Amazon in function of ‘development’ aimed at the exploitation of nature.

Among the countless issues affecting the Amazon and its peoples, mercury contamination has gained prominence due to the public health problem that has emerged in the region, affecting the human population, as well as fish and aquatic and land mammals, species that have a direct relationship with the rivers of the Amazon.

Mercury is considered one of the most dangerous metals for the environment and human health due to its high toxicity and mobility in different ecosystems. It has a great capacity to mobilize between different environmental compartments (atmosphere, soil, bodies of water, plants and animals), a long persistence in the environment and an ability to penetrate the food chain, mainly affecting fish, which are an essential source of nutrients for all peoples living in the Amazon, indigenous or otherwise.

There are three chemical forms of mercury: metallic, inorganic, and organic, with methylmercury (MeHg) being the most common form of organic mercury found in the food chain. MeHg is also the most toxic form to humans, as it mainly affects the central nervous system, although the liver, kidneys and cardiovascular, gastrointestinal, and immune systems may also be affected.

Though academic studies have shown that the Amazon’s soil has high levels of mercury in the natural environment, the main source of mercury contamination in waterways is the artisanal gold mining in informal mines. Mercury is used in the gold purification process, which contributes roughly 71% of all mercury emissions each year.

In addition, mercury is a key component for informal mining. Mercury is what unites the gold particles that are scattered in the environment. During the informal mining process conducted by dredgers (vessels loaded with machinery that separates gold by vacuuming the river bottom), the metal is released into the rivers in high quantities.

It is estimated that, for every kilo of gold, prospectors use about three kilos of mercury. We are talking about mercury in its metallic form, which combines with gold, forming an amalgam. As such, the prospectors extract the metallic gold by “burning” it, volatilizing the mercury, which is blown by the wind and later precipitates. Thus, the contamination of the waterways occurs from precipitation or from direct dumping into the riverbed, where microorganisms transform metallic mercury into methylmercury (MeHg) and absorb it. This is how the substance enters the food chain – from phytoplankton to mammals. Human exposure and/or contamination occurs mainly through the ingestion of fish contaminated with MeHg.

In the Tapajós River basin, which spans the Brazilian states of Mato Grosso and Pará, gold prospecting intensified in the 1970s and, since then, the activity has taken place mainly in the upper and middle regions of the Tapajós River. It is important to note that, in recent years, there has been an alarming rise in the number of prospectors operating on territories traditionally inhabited by indigenous peoples, with support from the Brazilian government. Tons of mercury have been dumped along the Tapajós River as a result of informal mining activities. The effect of this, in addition to the destruction of the territory and the impacts on the population’s food security and the ways of life of indigenous peoples, directly impacts the health of the population living on the Tapajós River basin.

Recent data from a survey of 462 people from different regions of the municipality of Santarém (PA), in the lower Tapajós region, which involved indigenous communities (the Tupinambá and Cumaruara peoples) and riverside communities (Tapajós-Arapiuns Resex), show that 75.5% have levels of Hg in their blood above that recommended by the WHO, with Hg levels ranging from 1.4 to 296.5 μg/L. This means that this population, even in a region where there is no presence of irregular mines, is exposed to levels high enough to have various toxic effects on human health.

Studies have shown that the population of the upper and middle Tapajós region is even more affected, especially the Munduruku people. It is important to note that there are few studies evaluating the effects of mercury contamination on human health. So diseases, or even deaths, are still presumed to be related (or not) to contamination from irregular mining, meaning such deaths will be slow and invisible.

It is important to note that there are few studies evaluating the effects of mercury contamination on human health. So diseases, or even deaths, are still presumed to be related (or not) to contamination from irregular mining, meaning such deaths will be slow and invisible.

Raquel Tupinambá

Mercury contamination as a result of gold mining reaches other regions in the Amazon, such as the Yanomami territory, which recently received media attention due to the humanitarian tragedy facing the people, with countless deaths of children and adults. To understand how the situation came to be, it is worth reading the report “Yanomami sob ataque: garimpo ilegal na Terra Indígena Yanomami e propostas para combatê-lo” [“Yanomami under attack: illegal mining in the Yanomami Indigenous Land and proposals to combat it”]’ developed by the Hutukara Yanomami and Wanasseduume Ye’kwana Associations, organizations representing the people, published on April 11, 2022.

The irregular mines that are destroying indigenous territories and contaminating rivers also affect other peoples in the Amazon. The Kayapó people in the Xingu region of Pará are facing the same situation and, in regions such as the Madeira River basin, people experience similar conditions.

Academic studies, and even documentary films, such as Jorge Bodanzky’s “Amazônia a nova Minimata?” [“The Amazon, the Next Minimata?”] which portrays the struggle of the Munduruku people to contain mercury contamination in the middle and upper Tapajós region, have warned of this serious situation, even suggesting that the Amazon is experiencing a situation akin to the case of Minamata, Japan, in which many people died from the effects of mercury contamination.

We need to talk seriously about this model of “development” that aims at the exploitation of nature and the transformation of indigenous and riverside populations into a cheap labor force. Capitalism proposes a model in which the few get richer and richer, while a large portion of society is made increasingly vulnerable and poorer. People, cultures and biodiversity are being killed off so that the capitalist system and the Western vision of development can continue.

There is a discussion of mining without the use of mercury and this would undoubtedly be a less harmful system of extraction. When considering mercury contamination alone, however, there has been talk of legalizing irregular mining, a cause for concern. We need to ask who is profiting from the exploitation of nature– in this case, the gold mining chain. Multinational companies? Business people? The great capital? Will the territories and forest areas continue to be destroyed? Will lakes of tailings be created in our territories that will soon kill off indigenous peoples and traditional communities in the Amazon, as has happened in other regions of the country?

We need to change this capitalist, developmentalist, genocidal logic. Rethinking and changing the way human populations live today represents the possibility of continued human existence on planet earth.

Opinion articles are the responsibility of their author.

About the writer

Raquel Tupinambá é mulher indígena, agricultora e militante pelos direitos indígenas. É uma liderança de seu povo e coordenadora do Conselho Indígena Tupinambá do baixo Tapajós Amazônia (CITUPI). Além disso, é doutoranda em Antropologia Social.