Mercury in the Amazon: The Hidden Cost of Gold Mining

The Modern Curse of Midas in the Amazon

In Greek mythology, Dionysus, the god of wine and celebration—granted King Midas the wish for the golden touch that everything he touched would turn gold. This power became a curse as food and water transformed into lifeless metal. Today, the Amazon faces a modern curse reminiscent of Midas’ tragic tale, but the transformation is far more insidious this time. In the depths of the Amazon, gold mining has brought a shadow—mercury contamination—unlike Midas’ touch, which turned objects to gold, the hands of miners leave behind mercury. This substance seeps into rivers and fish, threatening the health and survival of local communities. This toxic legacy mirrors the myth, turning sustenance into poison and prosperity into peril.

In the depths of the Amazon, fish that once sustained communities now harbor a hidden danger—mercury levels so high they threaten the neurological health of those who consume them.

Many mining activities discharge mercury (Hg) and methyl Hg [Methyl Hg, or methylmercury, is an organic and highly toxic form of mercury. Microbial activity in aquatic environments produces it and can accumulate in the tissues of fish and other organisms, eventually making its way up the food chain to humans.] into aquatic ecosystems, contaminating water, ecosystems, and marine species and negatively impacting human health.

Sources of Mercury Contamination

There are many ways by which Hg can reach aquatic ecosystems. Primary anthropogenic sources are artisanal and small-scale gold mining (ASGM) activities [ASGM refers to small-scale gold mining practices, often in developing countries, where miners use rudimentary methods to extract gold, typically involving mercury to amalgamate with the gold. This practice is a significant source of mercury pollution.], which uses Hg to amalgamate with gold, and deforestation and burning of organic matter can remobilize Hg from the soil into the food chain. ASGM activities account for approximately 12% of all gold produced worldwide, and to make 1 mg of gold, 2.5–3.5 mg of Hg are used, of which approximately 50% reaches streams and rivers as suspended sediment. ASGM activities also emit metallic Hg into the atmosphere, reduce into inorganic Hg, and precipitate into terrestrial and aquatic ecosystems.

The Bioaccumulation Process

While Hg remains in the soil, it is often in its inorganic form and less toxic, but when it reaches water courses, microorganisms may transform it into a more toxic form, methyl Hg. Methyl Hg can bioaccumulate [bioaccumulation is how certain substances, such as poisonous chemicals, accumulate in an organism’s tissues over time—this can occur when the substance is absorbed faster than the natural process eliminates it, leading to increasing concentrations within the organism.] in the tissue of organisms and through the food chain as other species consume them. It can also reach human populations through fish consumption. Methyl Hg is neurotoxic in human populations, and prenatal exposure can affect brain development, even at low exposure doses. Children exposed to methyl Hg may have delayed and impaired neurodevelopment and exposed adults may have impaired motor coordination, visual fields, speech, and hearing.

Case Study: Comparative Analysis of Mercury Contamination in the Tapajós and Negro River Basins

The Amazon basin is vast and diverse, with varying levels of mercury contamination across different regions. A comparative analysis between the Tapajós River Basin and the Negro River Basin highlights how various environmental factors and human activities contribute to mercury bioaccumulation in these areas.

The Tapajós River Basin, heavily impacted by artisanal and small-scale gold mining (ASGM), exhibits some of the highest levels of mercury contamination in the Amazon. Fish species in this region show mercury concentrations well above safe consumption limits, and local communities that rely on fish as a staple food are at significant risk of mercury poisoning. The high prevalence of ASGM activities, coupled with deforestation, has exacerbated the release of mercury into the ecosystem.

In contrast, the Negro River Basin, which has less intense mining activity and a more preserved forest cover, shows lower levels of mercury contamination. Although mercury is still present, bioaccumulation in fish and subsequent exposure to human populations are relatively lower compared to the Tapajós Basin. This difference underscores the importance of environmental preservation and the impact of human activities on mercury levels in aquatic ecosystems.

By comparing these two regions, it becomes evident that the intensity of mining activities and the state of the surrounding environment play crucial roles in determining the levels of mercury bioaccumulation. This comparison also highlights the potential benefits of stricter environmental protection measures and the promotion of mercury-free mining practices to mitigate the impact of mercury on local communities.

These case studies illustrate the real-world consequences of mercury contamination from mining activities, emphasizing the urgent need for effective mitigation strategies to protect the environment and the health of indigenous and local populations in the Amazon.

Impact on Human Health

Researchers found Methyl Hg in high concentrations in fish and shellfish, the primary sources of exposure to human populations. In the Guri hydroelectric reservoir in Venezuela, from 219 fish samples, 93 specimens showed levels above 0.5 ppm Hg, and up to 90% of the most appreciated piscivore fish in the region (Rhaphiodon vulpinus) showed average Hg levels of 2.7 ppm (0.17–8.25 ppm) – higher than those found in detritivorous and herbivorous fish species. Contamination through methyl Hg is exceptionally high in the Amazonian region. Several Amazonian communities have Hg levels critical for optimal neurological development. Dietary Hg intake has been estimated to be 1–2 μg/kg/day, considerably higher than the WHO recommendation (0.23 μg/ kg/day).

Case Study: The Yanomami Tribe and Mercury Contamination in the Amazon

In the remote Amazon rainforest, the Yanomami tribe, one of the largest relatively isolated indigenous groups in South America, has been facing a grave threat from mercury contamination. The source of this mercury is the rampant illegal gold mining activities that have plagued their territory. These miners used mercury to extract gold and dumped the resultant waste into nearby rivers and streams, critical water sources, and food for the Yanomami.

Researchers have found alarmingly high levels of mercury in the hair samples of the Yanomami people, particularly among children and women of childbearing age. The mercury levels in these individuals far exceed the World Health Organization’s (WHO) recommended safe levels, putting them at serious risk of neurological damage. Symptoms of mercury poisoning, such as tremors, memory problems, and impaired vision, have been increasingly observed in these communities.

The impact on the Yanomami tribe is not only a health crisis but also a cultural one. The contamination of fish, a primary source of protein, threatens the tribe’s traditional diet and way of life. Efforts to address this issue have included the Brazilian government’s initiatives to expel illegal miners from Yanomami territory and promote mercury-free mining techniques. However, the effectiveness of these measures remains limited, and the tribe continues to suffer the consequences of mercury pollution.

Mitigation Strategies

The reduction or elimination of Hg use in ASGM has received widespread attention. Less damaging options include amalgamating a gold concentrate rather than the whole ore and using “mercury-free artisanal gold,” in which gold is isolated by centrifuges and the gangue materials magnetically removed. Awareness and education about Hg poisoning in ASGM communities is also essential to ensuring adherence to such changes in ASGM technology.

Call to Action: Protecting Our Communities from Mercury Contamination

The dangers of mercury contamination, especially from mining activities, severely threaten human health and the environment. It’s time to take decisive action to mitigate these risks and protect our communities. Here’s how policymakers, communities, and individuals can contribute:

1. Strengthen Regulations and Enforcement:

Policymakers must enforce stricter regulations on artisanal and small-scale gold mining (ASGM) activities—this includes banning mercury in mining and ensuring that they shut down illegal mining operations. Strong environmental protection laws can help preserve ecosystems and prevent mercury from entering water systems.

2. Promote Mercury-Free Mining Technologies:

Governments and NGOs should invest in and promote the adoption of mercury-free mining technologies. By supporting initiatives introducing safer, alternative methods, such as gravity concentration or cyanidation, we can reduce the reliance on mercury and its harmful environmental impact.

3. Raise Awareness and Educate Communities:

Communities, especially those in mining regions, need to be educated about the dangers of mercury and how to protect themselves. Educational programs should focus on the health risks associated with mercury exposure and provide information on safer practices. Empowering communities with knowledge is vital to preventing mercury poisoning.

4. Monitor and Remediate Contaminated Areas:

Monitoring mercury levels in water, soil, and biota is crucial. Policymakers should allocate resources for the cleanup and remediation of contaminated sites. They can employ advanced techniques such as phytoremediation or engineered wetlands to restore affected ecosystems.

5. Support Research and Innovation:

Continued research into the effects of mercury contamination and the development of new mercury detection and removal technologies are essential. Governments, academic institutions, and private sectors should collaborate to fund research to understand the full scope of mercury’s impact and find innovative solutions to combat it.

6. Encourage Responsible Consumer Choices:

Individuals can also play a role by making informed choices, such as opting for sustainable products that do not contribute to mercury pollution. Consumers can demand cleaner, safer alternatives by supporting ethical companies and practices.

7. Advocate for International Collaboration:

Mercury contamination is a global issue requiring international cooperation. Countries must collaborate to implement the Minamata Convention on Mercury, sharing knowledge and resources to combat mercury pollution worldwide.

By taking these steps—we can significantly reduce mercury contamination, protect vulnerable communities, and preserve our planet for future generations. The time to act is now.