In the Name of Gold


Flag It!, Sao Paulo, Brazil

Would it sound more like an imprudent legislation or more like a deadly environmental policy? Such a hard question. In the margins of the rivers and in the margins of the law, small-scale gold mining is an activity that has a historical love affair with clandestinity. Comes from the Amazonas state an initiative that, for the first time in Brazilian history, provides a state regulation that brings the activity under the auspices of the law. The decision, however, raises doubts that divide scientists and policy makers. That’s because mercury, a highly toxic heavy metal, is now allowed to be used in mining activities – while the whole world moves forward to forbid or impose severe restrictions on the use of such element.

The saga of the gold miner has inspired many tales of greed, anger and violence. From land conflicts to environmental sins, mining stories usually have a common element: mercury – one of the most dangerous metals to the human health. From a scientist’s point of view, it is but a chemical entity of 86 protons. For the gold miner, however, it is much more than that. It is the silver liquid responsible for the alchemy of survival.

Like needles in a haystack, tiny gold pieces are naturally scattered around the soil along the Amazonian rivers. If the miner is to collect the precious metal, he has to take portions of that soil and add mercury to it. Liquid at room temperature – it is the only known metal with such attribute – mercury aggregates the little, elusive particles of gold and then form an alloy. After being exposed to heat, mercury evaporates and pure gold is finally in the miner’s hands.

It’s quite a rudimentary technology. But its omnipresence in small scale gold mining has worried the scientific community since the 60’s. Back then, mercurial toxicology was starting to be better understood. “Irreversible damage to the nervous system, not to mention the demise of certain brain areas associated with body motor-functions, hearing and visual aspects; these are some of the downsides that mercury frequently causes to the human health”, says biologist Wanderley Bastos, from the Federal University of Rondônia (Unir). “Once it is released into the ecosystem, the mercury becomes completely out of control, and we still have no technology to halt the biogeochemical processes that triggers its dissemination.”

Gold mining: a historical perspective

The relationship between mercury and small-scale gold mining has always been a classic issue for environmental debates. The latest intrigue, which brought light to an old debate, came in May 2012. The Amazonas Sustainable Development Secretariat (SDS) published a resolution that scared scientists and divided policy makers. It’s the Resolution 11/2012. In the wrong way of history, the document regulates the use of mercury in small-scale gold mining while many nations work to banish or impose severe restrictions to the use of this dangerous chemical. [Mercury is forbidden in Norway and strictly regulated in Sweden. In these countries, however, as in most of the developed world, mercury is used mostly in dental amalgam fillings. It raises the levels of mercury circulating in the blood]

Delicate issue. There is, in the end, good intentions in SDS’s action. It simply tries to regulate and discipline the mining activities within the state’s borders. Over the Amazonian broad distances, gold mining is an activity that flirts with illegality for centuries. Many generations’ survival have depended on the commerce of this precious metal. Families that inhabit remote areas had nothing but gold to sell to the outside world. Even so, the Amazonian states had never regulated the small-scale gold mining as a legal activity. “It happens, therefore, for decades without any sort of legal endorsement or public control”, explained public prosecutor Leonardo Macedo, from the Brazilian Federal Public Ministry (MPF).

The Resolution 11/2012 has been approved [in June 2012 by SDS]. With it, Amazonas has become the first Brazilian state to have a specific regulation for small-scale gold mining. Not bad, at first sight. But the scientific community didn’t like it at all. Civil society expressed concern. Even MPF worried.

Awkward law

Regulating the activity is admirable, but it can’t happen by allowing the disposal of mercury in the rivers and in the ecosystems”, reads an open letter signed by physician Ennio Candotti, director of Museu da Amazônia (Musa), in Manaus (AM). “We would like to inform you, governor, that mercury is a highly toxic chemical element, a fact that is not even mentioned in the new resolution.”

The new law has been accused of being overly permissive. Furthermore, it shows little concern about safety procedures and good environmental practices. In short, it says that the regions where mining activities occur should be previously examined by proper environmental assessments. It also mentions that the origin of the mercury has to be proven and the areas where miners work should be constantly monitored by the government. Besides, the mercury waste has to be sent to the closest city where it should be properly stored. The miner, according to the new text, is expected to use a device called retort – which is a type of oven. It heats the amalgam and safely separates the gold from it, in a closed system. Hence the mercury vapour, which is toxic, is prevented from being emitted to the atmosphere or breath by the gold miner. There’s still another advantage: retorts allow one to save the mercury left overs that would otherwise be disposed in the soil or in the water.

So it sounds like great news, at first sight. But what concerns scientists and policymakers is not what the new law says; rather, it is what it hides. “That’s because it completely lacks adequate mechanisms of environmental management”, warns Macedo. He mentions an example: even though it obliges the miners to use retorts, the text ignores the fact that this equipment should be certified by competent authorities so they assure it works properly. Furthermore, the new law does not forbid gold mining activities in areas already damaged or where the levels of mercury are naturally high.

Before a considerable amount of criticism, the Amazonas state stepped back and started dialogues”, tells Macedo. Busy semester for the Amazonian people, then. Debates and seminars had been organized in order to discuss the polemic new law. “That’s how we managed to alter the Resolution 11/2012 and substituted it by the Resolution 14/2012, in October, 2012”, currently in effect.

Not so bad

The new regulation forbids mining activities in areas where the concentration of organic matter [such as organic compounds from soil, plants and animals] is naturally high. It’s the case of many parts of the Rio Negro basin, for instance. Such environments facilitate the chemical reaction that transforms metal-like mercury (Hg) in methyl-mercury (CH3Hg+) – the element’s most hazardous chemical form. This reaction is called methylation. After that, mercury is rapidly absorbed by microorganisms and incorporated into the food chain. “It accumulates in fish tissues and, sooner or later, reaches human beings”, explains Bastos.

Now, with the new law, the mercury commerce is about to be regulated. Retorts will also have to be certified by Instituto de Pesos e Medidas [Institute of Weights and Measures] (Ipen). But there is another concern: “simply owning a retort, even though it is certified, is useless”, says Macedo. “After visiting mining regions in Amazonas, we stated that many boats and miners did have good retorts, but they were brand new ones; that is, they had never been used.”

If the pessimists are right, the Resolution 14/2012 has all it takes to become another useless law. That’s why it will go through a trial period. “We’ll evaluate it during the next three years”, says Macedo. “If we notice it is not fulfilling its initial intent, and that mercury is still causing major environmental damages to the ecosystems, we shall work to challenge the new law.” On the other hand, in case it works wonders – which requires a dose of optimism – it will be a milestone in the path of good mining practices in the Amazonian region. “It would be the first time Brazil successfully regulates an activity that has historically been out of the law”, envisions Macedo, although with some scepticism in his voice.

The resolution is intrinsically good”, said ecologist Bruce Forsberg, from the National Institute for Amazonian Research (Inpa). He has actively taken part in the recent debates on the issue and helped policymakers to reformulate the text. “My question is: will it really be possible to effectively monitor the implementation of such law?”

Contamination: the gold numbers

Many places in the Amazonia are already contaminated by mercury. Along Madeira river – which crosses through Porto Velho (RO) – and ends at Amazonas river – close to Manaus (AM) –, the presence of mercury in the organism of local inhabitants has been monitored for over a decade. Striking data has resulted . In São Sebastião do Tapuru (AM), some have rated 62 micrograms per gram [µg/g] of methyl-mercury in their bodies, when the safe limit established by the World Health Organization is about 7µg/g. Neighbouring municipalities have not brought better news. In Três Casas (AM), citizens marked 33,07 µg/g; in Vista Nova (AM), 25,69 µg/g; in Carará (AM), 18,13 µg/g; in Santa Rosa (RO), 13,99 µg/g; in Santo Antônio do Pau Queimado (RO), 14,69 µg/g. Ciência Hoje has organized this complete set of data (with dozens of different locations) in an interactive map, available at CH On-line. It is the first interactive map on the topic, in which the reader has access to the latest findings in terms of mercury contamination in the Madeira river basin. “The overall average of mercurial intoxication in isolated populations along Madeira river is 15 parts per million, that is, twice as much as what is considered normal by WHO”, says Bastos, very concerned.

Mercury and health issues

There are two ways of measuring mercury in the human body. If the metal vapour is inhaled, its presence will be shown in urine. If mercury is incorporated into the body via fish consumption, however, it will be verified in hair samples.

There are two different toxicological situations”, explained Bastos. Inorganic mercury (the vapour inhaled after the amalgam is heated to separate mercury from gold) causes major damages to the kidneys and to the respiratory system. “Although miners still suffer from it, such problem nowadays is not as bad as it used to be in past decades”, says Bastos. Currently researchers are much more concerned with the organic form of the metal – methyl-mercury. Once inside the organism, it stays there for long and it’s hardly excreted, staying inside the body for the rest of one’s life in most cases. That’s precisely why mercury contamination is a major public health issue for more than 50 years now”, writes biologist Sandra Hacon, from Fundação Oswaldo Cruz (Fiocruz). “Mental retardation, cerebral palsy, deafness, blindness and all sorts of sensorial damages are associated with contamination by mercury.”

In the Amazon, the more isolated a population is the bigger its fish consumption”, says Bastos. The Brazilian averageconsumption of fish is about 60 to 90 daily grams. But scientists from Unir calculated that, in some Amazonian regions, the fish consumption per capita can reach 406 daily grams. “Probably very few populations in the world have such a high average”, according to Bastos.

But there’s a compelling mystery in this data”, says Bastos. “Even though mercury is a neurotoxic element, some local populations in the Amazon show none of the classic symptoms of the mercurial toxicology.” Researchers therefore believe other components of their diet may prevent them from what mercury should cause to their health. A feasible hypothesis is selenium. It’s found in local nuts as well as in local fruits, and they might be responsible for keeping those people safe from mercury contamination. But Bastos reminds us that this is still an on-going research. “We know little about it.”

Mine map

Brazilian industrial gold production – in big industrial mines – is concentrated in Minas Gerais, Goiás and Bahia. When we look at small-scale gold mining, though, Mato Grosso, Pará and Rondônia are the main producers. Tapajós basin, as well as Madeira basin, are among the most productive areas.

In big industries, gold production uses no mercury. They use cyanide instead. This chemical compound, made from carbon and hydrogen atoms, is diluted in an aqueous solution which is then showered onto the raw material. After some chemical reactions that segregate the pure gold, the precious metal is then incorporated to a liquid solution and separated by an electrolytic process.

Some argue that the cyanides should be used as an alternative to the use of mercury in small-scale gold mining. Not everyone would agree. “It’s quite a complex process, which requires precise calculations and many safety measures; moreover, cyanide is highly toxic as well”, explains sociologist Armin Mathis, from Federal University of Pará (UFPA). He’s been studying the social impacts of gold mining for several decades.

How many people work in this field in the Amazon? “There’s no official data regarding the precise number of small-scale gold miners”, a representative of the National Department for Mineral Production (DNPM) toldCiência Hoje. “And the unofficial numbers are quite divergent”. What we do know is that there are 853 permission documents that had been given to people or companies eager to exploit gold in the region. It’s called Permissão de Lavra Garimpeira (PLG). Nowadays, DNPM has more than 16 thousand applications from people or companies who want to start in this business. “I suppose there are currently about 20,000 or 30,000 people working directly in small-scale gold mining in the Amazon”, estimates Mathis. In any case, the truth is that this number – whichever it may be – is certainly skyrocketing. The high gold prices in international markets over the past years have motivated many to give up everything to try their luck in this activity.


I believe it is possible to get rid of mercury use in any mining process”, argues Bastos. “The less mercury emissions, the less damage to the ecosystems and to the human beings we’ll see.” Some argue, however, that there’s no alternative. Would that be the case? “Not really”, responds Macedo. “We do have alternatives, but none of them is easy to implement.”

There are gravimetric techniques”, mentions Bastos. They allow the miner to separate gold from sediment based on vibrating table that uses mechanical principles: as it vibrates, the heavy parts of sediment will be separated from the lighter fragments. There’s a downside, however. These tables require stable terrain – and boats that miners use are not always compatible with such devices. Even so, there are some cooperatives that have already succeeded in implementing these good practices some boats. In Humaitá (AM), Cooperativa dos Garimpeiros da Amazônia (Coogam) uses this technology in some vessels. “Environmental risks are minimized since it is a mechanical process of separation, not a chemical one”, says Geomário Leitão, the institution’s manager. “The Brazilian government could stimulate studies in this direction”, suggested Bastos.

International scene: mercury, markets and conspiracy

The United Nations coordinates some efforts so that nations can better regulate and reduce the sales of mercury in the world. “Unfortunately, some of these efforts have been frustrated by a strong lobby on part of the developed countries, and the weird thing is that Brazil is apparently leading this lobby”, says Forsberg. “But since I’m an outsider, I prefer not to comment any further on that”, jokes the ecologist. He is North-American. According to Forsberg, the nation which is probably most interested in reducing or banishing the production and commerce of mercury worldwide is the United States – they already have enormous, strategic stocks of this element, key to military purposes. “If the mines currently operating in China, Russia and Spain close their doors, it will be great business for the United States, because they’ll then dominate the market”, says the ecologist. Would these debates involving mercury be, therefore, some sort of geopolitical conspiracy strategy? ‘Well, it depends on how suspicious you are”, jokes Forsberg.

When it comes to diplomacy, the optimistic ones may see good news indeed. “Brazil is taking part in the preparation of an international legally binding document on mercury regulation”, Letícia Reis de Carvalho director of Departamento de Qualidade Ambiental, part of the Environment Ministry (MMA)., told Ciência HojeLast January, representatives of 140 countries gathered in Geneva, Switzerland, to prepare a document which will guide international policies on mercury use worldwide. It’s the Minamata Convention. [Agreed by 147 nations in January 2013, the final document was released in the 11th of October. So far, 92 countries have actually signed it, and the convention will enter into force after 50 nations have ratified the document. Brazil is a signatory.]

The proposal talks about reduction rates [of mercury emissions]. Carvalho pointed out that the text recommends actions to eliminate the process of gold amalgamation in open environments; it urges that the activity be properly regulated and that good environmental practices be implemented to avoid mercury exposure. It also endorses the need for research and development of new methods for gold mining without mercury.

Regulating the use of mercury in small-scale gold mining is one of our biggest challenges ahead”, says Carvalho. “The government believes that formalizing the activity and reducing the mercury emissions will take us to a better environmental scenario”. But wait a moment… What do miners themselves think of this whole debate? “Have you ever considered working without mercury?”we asked one of the miners in the Amazon region. “No”, he promptly answered. “I’m a miner for 30 years; my father and my grandfather have always used mercury, it has always been like that.”

Henrique Kugler | Ciência Hoje | Rio de Janeiro 


Check Ciência Hoje On-line for the interactive map Amazôniacontaminação por mercúrio. It’s the first online publication that maps the most recent data on mercury contamination in the Madeira river basin. We have also prepared the series of complementary stories Rastros do mercúrio, which tell us where else mercury is used other than in small-scale gold mining. The series also mentions the impacts of mercury in hydropower projects, as well as the historic accidents involving mercury over the 20th century.

Suggested readings:

  • Um panorama dos estudos sobre contaminação por mercúrio na Amazônia legal no período de 1990 a 2005. S. Hacon, P. R. G. Barrocas, A. C. S. de Vasconcellos, C. Barcellos, J. C. Wasserman, R. C. Campos. Geochimica Brasiliensis, Vol 23, N.1, 2009, Sociedade Brasileira de Geoquímica

  • MORIYAMA, V. ‘Vila da ressaca: os restos de um sonho dourado’ in O Eco,14/03/2013.