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Mercury contamination in Brazil: a growing challenge

A problem that requires urgent attention from authorities and society


This highly toxic heavy metal has affected several ecosystems and poses a threat to human health.

Mercury contamination is an environmental and public health concern worldwide. In Brazil, a country rich in natural resources, the presence of mercury and its consequences have been the object of study and monitoring for decades. Contamination occurs mainly due to mining activity, especially in regions where gold extraction is intense. Mercury is used to separate gold from sediments, forming an amalgam that facilitates the extraction of the precious metal. However, this practice has devastating consequences for the environment and poses a threat to health. One of the main problems is the contamination of rivers and fish. The mercury released during the mining process ends up being deposited in the waters. Fish, in particular, accumulate the metal in their tissues over time and when consumed can pose a significant health risk, causing neurological damage and affecting fetal development, for example. Pará, in northern Brazil, is one of the most affected regions. Gold mining in the state is intense, and rivers in the region have alarming levels of mercury. Riverside communities that depend on fishing as a source of livelihood are being particularly affected, and thus face health problems and food insecurity.

The adverse impacts of this problem on public health have become increasingly worrying. Mercury contamination has a number of harmful effects on human health. It can affect the central nervous system, resulting in brain damage, learning problems and cognitive development in children exposed during pregnancy. In addition, it can cause kidney, cardiovascular and immune disorders, impairment of vision and the respiratory system. Mercury circulates in the environment, in different compartments, it is in the water, in the soil, in the rain, in the clouds, in fish, in all the different animals that live in aquatic environments, both in rivers and in the sea or lakes. To learn more about the subject, the press office of the Brazilian Society of Tropical Medicine (SBMT) interviewed Dr. Paulo Cesar Basta, Doctor and Researcher in Public Health at the Oswaldo Cruz Foundation (Fiocruz) and Coordinator of the Indigenous TB area of ​​the Brazilian Tuberculosis Research Network REDE-TB.

Check the interview in full.

SBMT: What is the extent of mercury contamination in Brazil, both in terms of affected geographic areas and exposed populations?

Dr. Paulo Cesar Basta: It is a question that I would say does not have a clearly defined answer, because we do not have an exact dimension of the extent of these areas contaminated by mercury in Brazil. The official data available today are completely outdated. There is an information system of the Ministry of Health, called Information System for Health Surveillance of Populations Exposed to Contaminated Soil (SISSOLO), which systematizes the information and monitors the identified populations, through the continuous registration of potentially contaminated areas, enabling the construction of environmental and health indicators in virtually the entire country. However, the data that are available for public consultation are at least ten years out of date. But according to reports, the main affected areas are in the Southeast, Northeast and South, mainly due to the industrial plants located in these regions. Many industries that work in the production of chlorine-soda, light bulbs, in the manufacture of batteries in which mercury is used directly in production or that is found as residue from the production process end up contaminating some areas.

With regard to mining, we do not have a clear dimension of the extent of the problem, since a good part of the gold mining activities carried out in Brazil today are illegal. Monitoring carried out by MapBiomas informs that currently more than 50% of gold mining activities in the country are illegal. That is, they come from clandestine mines that operate illegally, especially in Indigenous Lands (TI), in conservation units, and in areas of environmental preservation, which are considered Union lands. In these locations, unfortunately, we do not have any official record of the use of mercury and how it is used in these operations, nor the amount of mercury that is generated as waste from the process and that will pollute the environment. There are estimates that at least 80% of the mercury circulating today in the Amazon comes from these illegal mining activities. Some studies at the Federal Police indicate that for every kilogram of mercury used by prospectors to identify gold, two to eight kilograms of mercury are used. On average, about three kilograms of mercury are used for every kilogram of gold identified. Some Federal Police reports report that 600 kilos of illegal gold were seized, and of these, more than two tons of mercury were used. This is just a small example of a flagrante delicto that occurred in the region of the Tapajós River, in Pará.

The most affected Indigenous Lands today are: firstly, the Kayapó TI, located in the state of Pará; secondly, TI Munduruku, which is also located in the state of Pará; and, in third place, comes the Yanomami TI. In addition to these three main affected Indigenous Lands, there are areas in Rondônia that are also subject to contamination, Amazonas, Mato Grosso and Amapá. That is, in virtually all states of the Legal Amazon, with the exception of Acre, there are records of indiscriminate use of mercury in illegal gold mining activities.

And, unfortunately, this problem is not restricted to the Brazilian territory, to the Brazilian Amazon. Several countries bordering Brazil, in the Amazon Region, also record these activities, as is the case of Peru, where mining is very important, Colombia, Venezuela and the Guianas. It is a problem that is widespread in the Pan-Amazon region. The work we did recently identified the presence of high mercury concentration levels, reaching 1/5 of 1010 fish samples that were collected from 17 cities, including six capitals of the Brazilian Legal Amazon. This gives a clue to the size of the extent of this contamination and demonstrates that there is a wide spread of mercury in Brazilian territory, especially in the Amazon, due to illegal gold mining activities. In any case, we cannot forget the existing environmental liabilities in the industrial plants located in the Southeast, South and Northeast regions.

SBMT: Which population groups are most vulnerable to the effects of mercury contamination?

Dr. Paulo Cesar Basta: Although mercury is a chemical contaminant, that is, it has no biological function for humans, it is not necessary for any stage of metabolism or any physiological activity, when it is present in the human body, its only function is to act as a contaminant and cause damage to tissues, organs or systems where it will be deposited. For anyone, mercury acts as a toxic element, but the most vulnerable population groups are mainly women of childbearing age and children. This happens for a very particular reason. When a woman is of childbearing age, especially when she is pregnant, and she eats contaminated fish, the mercury that is in the muscle tissue of the fish, in the flesh of the fish, will be ingested along with other nutrients, omega threes, amino acids, carbohydrates , and together with these nutrients, methylmercury will be absorbed, a particular form of mercury that is concentrated in the muscle tissue of fish. Methylmercury, when ingested by the pregnant woman, falls into the bloodstream and will be distributed throughout all the organs of the system, and as it accumulates in certain organs, it will cause lesions, which will be manifested through different signs and symptoms. The most important thing in the case of the pregnant woman is that the mercury circulating in the blood passes to the baby, who is being gestated in the mother’s womb, through the placenta, the umbilical cord. That is, the circulating mercury in the mother’s body will affect the baby that is being formed in the mother’s womb.

Studies indicate that the concentration of mercury in the baby’s brain reaches figures 5 to 7 times greater than the levels of mercury circulating in the mother’s blood. Such exposure in the prenatal period can cause serious problems for the child. Depending on the level of exposure to mercury, signs and symptoms have a wide spectrum of presentation ranging from mild clinical manifestations to severe manifestations. Considering the serious manifestations, if the woman is very contaminated, she may not be able to carry the pregnancy to term. The woman can have recurrent miscarriages. In cases of extreme contamination, the child can be born with deformities, congenital malformation, cerebral palsy, very important health situations that can be observed at birth.

When exposure to mercury is not so high, the child may have mild symptoms, and at birth, it will appear to be a normal child, without defects or deformities. But as time goes by, it is noticed that the child takes time to hold his head up, sit down, crawl, take his first steps, speak his first words. When the child grows a little older, and is two or three years old, it is noticed that he does not communicate normally with others, he does not play, he does not play the same games as children of the same age who were not affected by mercury exposure. . When reaching school age, the child begins to have difficulties in learning, concentration and interpersonal relationships with peers. Therefore, when we investigate this case, we realize that this child may have been exposed to mercury during the prenatal period. This has serious consequences that can last a lifetime.

Studies point out that for each microgram of mercury identified in a hair sample of a pregnant mother, the child in the womb will have a loss of 0.18 points in the intelligence quotient (IQ). So if the woman is heavily contaminated, for example, with 30 micrograms of mercury for each gram of hair, which is not such a rare situation to happen in the Amazon, that child will have her IQ severely impaired. As mentioned above, this cognitive loss will last for a lifetime and this child will have problems at school, will have difficulties in completing elementary school, high school, and with that will have problems accessing higher education, and as a consequence you will have a good job, a good income, and you will have problems supporting your family. The consequences of exposure to mercury will extend throughout life, making social inequalities increasingly evident, contributing to the concentration of income and the increase in poverty.

SBMT: What are the strategies and policies adopted in Brazil to mitigate mercury contamination?

Dr. Paulo Cesar Basta: There is specific environmental legislation that regulates mining activities in Brazil, Law 7,805, of 1989. According to this legislation, there are two models for mineral exploration in the country: one of them is the mining concession for large companies can operate and mine in the national territory. These companies must present environmental impact studies, reports on the impact on the environment, they must respect a series of legal instruments, inform the amount of mercury that is used in the mineral extraction processes, how this metal is handled, if it is recaptured from the environment, if there is any remediation work for the contaminated areas, in short, there is clearly defined legislation for this modality of mining concession. In turn, the other modality provided for in Law 7.805 is the mining permit, the PLG. This permission is given to individuals or cooperatives of prospectors to operate in demarcated areas, defined by the National Mining Agency (ANM). These areas are outside Indigenous Lands, conservation units, environmental protection areas, international border lines, and vacant lands or lands of specific destination, considered lands of the Union, of the Federal Government. That is, there can be no mining in these territories. For industrial plants there is also, in theory, severe environmental and health legislation that regulates these activities and must be strictly complied with. In addition, in Brazil we still have some collegiate ordinances and resolutions of the National Health Surveillance Agency (Anvisa) that regulate the commercialization of food products, and among these resolutions there is one aimed at controlling the levels of mercury that can be observed in fish. This legislation provides that fish, for example, can only be marketed if they contain a maximum of 0.5 micrograms of mercury for each gram of muscle tissue. If the mercury level is above this value, it should not be marketed, as it may pose a risk to the health of consumers. As I mentioned above, our study evaluated 1,010 fish from 17 cities in the Amazon, and 1/5 of these fish, more precisely 21.3%, had mercury levels above the index of 0.5 micrograms established by Anvisa, therefore, these fish should not be marketed.

Still within Anvisa, there are laws that define the use of metals, for example, in cosmetic products and pharmaceutical medical products. In the past, we had mercury in thermometers, in devices for measuring blood pressure, often ethylmercury (another form of organic mercury) was used as a preservative in vaccines and some medications, and in addition, mercury was and continues to be used in dentistry (amalgams fillings, produced with silver nitrate and mercury). In 2013, the United Nations (UN) enacted the Minamata Convention. The elaboration of this convention was inspired by the tragedy that occurred in the 1950s, in Minamata Bay, Japan, when the international scientific community became aware of the damage caused by mercury contamination to the local population. At the time, hundreds of people died, thousands were affected by mercury, there was almost an epidemic of children being born with congenital malformations, cerebral palsy, and serious neurological conditions resulting from this contamination. Since that event, the international community has been made aware of the problem, until in 2013 the Minamata Convention was enacted, which provides for the banning of mercury from all industrial processes on the planet, whether in the medical pharmaceutical industry, in the production of light bulbs, in the chlor-alkali industry, in the production of cells and batteries, in all industrial processes, without exception, with limits being established for these activities to be discontinued. Today, more than 140 countries are signatories to the Convention, Brazil being one of them. In our country, the Convention was internalized as Brazilian legislation in 2018, still under the management of former President Michel Temer.

In this way, an international commitment was established by Brazil to eliminate all mercury emissions into the environment. Within the Minamata Convention, there is a specific chapter that deals with artisanal or small-scale gold mining (garimpo). Brazil has publicly assumed, together with the international community, that it is also a signatory to the Minamata Convention and that gold mining in the country was not insignificant. The document delivered to the UN publicly assumed this, and from this delivery, which took place in 2021, we have three years to present a management plan to eliminate mercury in artisanal mining.

These are some strategies and policies adopted in Brazil. However, the Ministry of Health (MS) does not have a national plan for the eradication of mercury, there are no reference centers for welcoming affected populations, there are no specific training and updating courses for professionals working in the Unified Health System (SUS ). Our field experience in the Amazon shows that the vast majority of professionals do not have any knowledge about this topic, do not know how to recognize a patient with signs or symptoms suspected of contamination. That is, there is a huge gap in the training of these professionals, whether doctors, nurses, nutritionists, psychologists, dentists, etc. Thus, our research group at Fiocruz presented the new management of the Federal Government, through the Ministry of Health, with a proposal, a plan to eradicate mercury contamination in Brazil.

SBMT: What preventive measures can be recommended to reduce exposure to mercury and protect the health of the Brazilian population?

Dr. Paulo Cesar Basta: I would say that integrated actions are needed that must be carried out concurrently by different bodies, institutions and ministries. Dealing with mercury contamination should not be understood as an exclusive responsibility of the Ministry of Health. The Ministry of Justice, for example, has to combat illegal mining in Indigenous Lands and in other areas of environmental preservation and conservation units, which are Union lands, as mentioned earlier. This fight requires the disintrusion of these areas that are now invaded, that is, the government has to remove prospectors from these territories and ensure that they do not return, nor that they leave and migrate to other places. This was a recent phenomenon that happened in Brazil in the 1980s, when there was an interruption in operations at the Serra Pelada mine, in Pará, and mining activities stopped in that region, there were thousands of workers working in this activity. With the interruption of activities, there was a massive migration process, causing thousands of people to spread out in other areas of the Amazon. Part of this wave of prospectors occupied the region of the Tapajós River valley, in Pará, and another part migrated to the Yanomami Indigenous Land. This phenomenon became known as the first gold rush in the Amazon, responsible for the first invasion of the Yanomami Territory. After being removed in the early 1990s by the Collor government, the garimpeiros spent more than 20 years without working in the Yanomami TI. However, around 2013-2014, with a significant increase from 2016 onwards, the peak of invasions was reached in 2022, with significant numbers of miners returning to work illegally in Yanomami Land again. The work that is being carried out today at the site, by the Ministry of Justice, has to be carried out in other areas of Brazil, such as in the Kayapó Indigenous Land, in the Munduruku Indigenous Land, in Amapá, in Rondônia, and in Amazonas. This is an important action that the Ministry of Justice needs to take together with the Federal Police and the Brazilian Institute for the Environment and Renewable Natural Resources (IBAMA) in all invaded areas in the Amazon today.

The Ministry of the Environment, in turn, must monitor the areas that are affected, seek to develop a set of measures to remediate the contaminated areas. In addition to interrupting mining, the devastated areas that were contaminated by mercury need to be reforested. The forest plays an important role not only in mitigating climate change and controlling the planet’s temperature. In the same way that trees sequester carbon circulating in the atmosphere, they also sequester mercury and store this metal in an inert form within their trunk, in their roots, in their leaves. Thus, it is important to have defined actions for the remediation of contaminated areas. These actions must be planned and developed by the Ministry of the Environment. Once the miners are removed from the illegally invaded areas, the Ministry of Cities must think of strategies to ensure that the people who worked in the garimpo are incorporated into the regional economy. Until this reception process takes place, these people need to have access to government social benefits, such as the Bolsa Família Program, among other benefits. In addition to access to government support programs, sustainable development projects must be created, valuing the vocations of the environment and the people who live there, such as, for example, encouraging productive chains, the green economy of the forest, with the sale of nuts, cocoa, cupuaçu, açaí, mushrooms, and many other products that can be sustainably produced in the forest and that, in addition to feeding people, can generate income for families.

Considering the frequency of contaminated fish, it is important for the Ministry of Fisheries to act in order to create insurance to protect the fishing community. With an increasing amount of fish contaminated by mercury and a possible ban on the sale of these fish, the fishing community will suffer serious impacts from a socioeconomic point of view. Therefore, it is essential to think about actions to protect fishermen. Just as there is closed insurance, which recognizes that at certain times of the year the fisherman cannot fish to ensure the reproduction of fish and the supply of communities, one should think about a kind of mercury insurance, for example, applied in situations where which fishing areas are affected by contamination.

Last but not least, comes the actions that must be developed within the scope of the Ministry of Health. These actions range from the preparation of recommendations for the safe consumption of fish, oriented towards the ingestion of less contaminated species (non-carnivorous fish), to the elaboration of a national program for the eradication of mercury contamination. This program has to foresee the carrying out of integrated actions, which involve the construction of reference centers in strategic points, especially in the most impacted areas of the Amazon, in order to welcome the affected populations that already show signs and symptoms resulting from chronic exposure to mercury . These reference centers need to have professionals in sufficient quantity and quality to provide adequate care and care for the affected populations, carry out health care at all levels of complexity, guarantee the performance of complementary exams, when necessary, as well as initiate specific treatments, when indicated. For this to happen, it is necessary to offer training and refresher courses for top professionals on an ongoing basis, so that they are qualified to meet local demands, based on the most current scientific evidence. It is also necessary that existing cases of contamination are notified and entered into official statistics, and thus become part of the databases of the Notifiable Diseases Information System (Sinan). Today, unfortunately, this type of notification is not occurring, so there are no official statistics on the problem of contamination. This fact results in an important record, which covers the current threat to national public health.

Finally, there are several actions, several measures that must be carried out in an integrated way between different institutions and ministries of the Federal Government.

SBMT: What are the impacts of mercury contamination on human health and which organs are most affected by exposure? Is there scientific evidence on the long-term effects of chronic mercury exposure on human health?

Dr. Paulo Cesar Basta: The mercury that is inside fish is found in a specific form, organic mercury, which is also called methylmercury (MeHg). This form of mercury is different from the metallic mercury, also known as liquid silver, quicksilver, or elemental mercury (Hg0) that is in the prospector’s hand. There are studies that point out that for every kilo of gold found by the prospector, an average of three kilos of metallic mercury are used. That is, these two excess kilos of metallic mercury are released into the environment, without any type of care or prior treatment. This metallic mercury released into the environment falls into the river bed, and as it has a density 13 times greater than that of water, it does not mix easily. So, it undergoes a lot of sedimentation, it goes down the water column and goes to the bottom of the river bed. There, metallic mercury undergoes a transformation process mediated by microorganisms and becomes organic mercury, which is methylmercury. Methylmercury, in turn, enters the food trophic chain, affects all living beings that inhabit the river, and thus will be deposited in the muscle tissue of the fish, in the flesh of the fish, exactly in the part that we use to feed ourselves. Human beings, when eating fish, will ingest methylmercury, which, when falling into the bloodstream, can be distributed throughout the body and settle in different organs or systems, mainly affecting the central nervous system (brain), the cardiovascular system, the kidneys, the endocrine system, different glands, the liver, in short, leading to different clinical manifestations depending on the affected organ or system. This makes it difficult for health professionals to clearly identify suspected mercury contamination.

Signs and symptoms have a wide spectrum of clinical manifestations, ranging from mild signs and symptoms to more severe forms. In the previous question, we talked about the effects on vulnerable populations, particularly the long-term effects that can affect women of childbearing age and children. The main neurological manifestations can be didactically divided into three components: sensory, motor and cognitive changes. Sensory alterations range from a decrease in tactile, thermal and painful sensitivity in the extremities of the hands and feet, to the presence of a metallic taste in the mouth, permanent noise in the ear, loss of peripheral vision, to some signs of dizziness, chronic headache, irritability, insomnia, humoral lability, among other signs and symptoms. Motor changes include tremors in the extremities, which gradually turn into weakness, this can progress from the hands to the arms, from the feet to the legs, and, suddenly, the person is no longer able to hold a light weight such as a plate of food, cannot climb stairs, take a longer walk. As the contamination progresses, the person may have severe tremors, and slowly lose leg movements, requiring the use of a wheelchair or other support equipment, thus simulating Parkinson’s syndrome. In cognitive alterations, adults begin to have memory problems, forgetfulness, difficulty in retaining content and learning, and as the disease evolves, it gets worse, it begins to present conditions similar to Alzheimer’s syndrome.

These are important clinical events with different manifestations, which together end up making it difficult for health professionals to identify cases. For this reason, we reinforce the importance of offering regular refresher courses for health professionals who work in the affected areas. There is much evidence on the long-term effects of exposure to mercury, notably those caused by mining on the environment. These effects include, in addition to the devastation of the forest, the contamination of fish and other animals. More recently, different authors have been working on the perspective of demonstrating effects on human health. Our research group at Fiocruz has recently been dedicated to studying the effects on the health of indigenous populations and we have already accumulated important works that reveal unequivocal evidence of the association of neurological symptoms and symptoms, as well as damage to child neurodevelopment in the Yanomami Indigenous Lands and Munduruku.

SBMT: Can the effects of mercury contamination vary depending on the dose, duration and form of exposure, as well as the individual characteristics of each person?

Dr. Paulo Cesar Basta: Yes, all of this actually influences the effects. The effect of exposure is dose dependent. The higher the exposure dose, the greater the damage to the affected tissues, and therefore, the greater the clinical manifestations and symptoms presented. The duration of exposure is another important factor to consider. There are acute exposures that are basically concentrated in workers who use metallic mercury, since the manipulation of this chemical element can cause acute intoxication, in case there is a cut or scratch on the prospector’s hands. In such cases, mercury can fall into the bloodstream and cause serious disorders.

In addition, the metallic mercury used to facilitate the process of identifying gold in sediments, the one that forms the amalgam, when heated, evaporates, generating metal smoke. If this smoke is inhaled, the metal can affect the lungs causing chemical pneumonia. In turn, the metallic mercury that is inhaled falls into the bloodstream and can be distributed by different organs and systems, and can affect the central nervous system (vertigo, convulsions, hallucinations), the kidneys (acute renal failure), generating a picture of severe acute intoxication with severe consequences. In these cases, very aggressive interventions are necessary, such as: hospitalization, use of artificial respirators, chelation agents to reduce the amount of circulating mercury, among others. On the other hand, there is chronic exposure, which occurs through the digestive tract, and is basically associated with the consumption of contaminated fish, as mentioned above.

Know more:

Science and Poetry Project: https://www.youtube.com/@cienciaepoesia/videos

Technical Note on mercury contamination of fish in the Amazon: http://bit.ly/NotaGarimpo

Human Mercury Exposure in Yanomami Indigenous Villages from the Brazilian Amazon: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028914/

Neurological Impacts of Chronic Methylmercury Exposure in Munduruku Indigenous Adults: Somatosensory, Motor, and Cognitive Abnormalities: https://pubmed.ncbi.nlm.nih.gov/34639574/

Mercury Exposure in Munduruku Indigenous Communities from Brazilian Amazon: Methodological Background and an Overview of the Principal Results: https://www.mdpi.com/1660-4601/18/17/9222

Impacts of the Goldmining and Chronic Methylmercury Exposure on the Good-Living and Mental Health of Munduruku Native Communities in the Amazon Basin: https://pubmed.ncbi.nlm.nih.gov/34501591/

Genetic Polymorphism of Delta Aminolevulinic Acid Dehydratase (ALAD) Gene and Symptoms of Chronic Mercury Exposure in Munduruku Indigenous Children within the Brazilian Amazon: https://pubmed.ncbi.nlm.nih.gov/34444495/

Health Risk Assessment of Mercury Exposure from Fish Consumption in Munduruku Indigenous Communities in the Brazilian Amazon: https://www.mdpi.com/1660-4601/18/15/7940

Mercury contamination eradication plan presented to the Ministry of Health:  (Click here)