Gold Mining's Mercury Pollution: A Toxic Truth

Mercury pollution from gold mining is a serious environmental issue. Between 10 and 20 million people use mercury to mine for gold in over 70 countries, making it a global problem. Gold shops, which play an important role in the artisanal gold production process, are also involved in the mercury trade and are a key source of mercury emissions. Mercury is used to extract gold from ore as an amalgam, which is then heated to evaporate the mercury and leave behind gold. However, this process releases toxic vapours, causing mercury pollution and posing a direct health threat to miners who inhale the fumes. Mercury pollution from gold mining has been linked to long-lasting social, economic, and environmental consequences, including contamination of water and soil, and accumulation in food staples such as fish.

Mercury Capture System (MCS)

Mercury is a neurotoxin that has long poisoned gold miners and poses a direct health threat to them. Artisanal and small-scale gold mining (ASGM) operations, which are often unregulated and unsafe, generate 37% of global mercury pollution (about 838 tonnes annually), more than any other sector.

Miners use mercury to bind to gold particles in ores, creating a silver amalgam that is then heated to evaporate the mercury, leaving behind gold but releasing toxic vapours. These vapours escape into the atmosphere and can migrate across the world, settling in lakes and waterways and entering the food chain through fish.

To address this issue, the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy's Argonne National Laboratory (ANL) developed the Mercury Capture System (MCS). The MCS is designed to be a simple, highly effective, and inexpensive system that can be easily constructed using locally available materials. The system features a series of baffle plates that capture large mercury particles and channels the vapourised mercury droplets into a converted steel drum, where the mercury is condensed and captured. The MCS can be retrofitted to nearly any type of hood that gold shops use to funnel mercury vapours out of their shops.

The MCS has been tested at gold shops in the Amazon region, with the Argonne/EPA team working with locals to determine the best configuration of fume hoods and exhaust chimneys to capture mercury vapours. The system is inexpensive to build, costing less than $500 in materials, which is key to its success as gold shops are more likely to adopt it if it is affordable. By capturing mercury during amalgam burns, the MCS can help to significantly reduce emissions and limit the release of mercury into the environment.

Minamata Convention on Mercury

Mercury is a naturally occurring element that has long been known to be toxic to human health and the environment. Large-scale public health crises due to mercury poisoning, including the Minamata disease in Japan, drew attention to the issue. The Minamata Convention on Mercury, named after the bay in Japan where mercury-tainted industrial wastewater poisoned thousands of people, is a multilateral environmental agreement that addresses specific human activities contributing to widespread mercury pollution.

The Minamata Convention on Mercury is the most recent global agreement on environment and health, adopted in 2013. The text of the convention was adopted by delegates from over 140 countries in 2013 after three years of negotiation. The convention entered into force in 2017, and as of September 2024, 151 countries have joined. The objective of the convention is to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. It contains provisions that relate to the entire life cycle of mercury, including controls and reductions across a range of products, processes, and industries where mercury is used, released, or emitted.

The Minamata Convention provides controls over a myriad of products containing mercury, the manufacture, import, and export of which will be prohibited by 2020, except where countries have requested an exemption for an initial five-year period. These products include certain types of batteries, compact fluorescent lamps, relays, soaps, cosmetics, thermometers, and blood pressure devices. The convention also addresses the direct mining of mercury, its export and import, its safe storage, and its disposal as waste.

The Minamata Convention on Mercury is particularly relevant to gold mining, as mercury has long been used in artisanal and small-scale gold mining (ASGM) to extract gold from ore sediment and rock deposits. These operations, often unregulated and unsafe, generate 37% of global mercury pollution (838 tons a year) – more than any other sector. The Minamata Convention requires that party nations reduce and, where feasible, eliminate the use and release of mercury from ASGM. It also requires nations to control mercury air emissions from coal-fired power plants, coal-fired industrial boilers, certain non-ferrous metals production operations, waste incineration, and cement production.

To address mercury pollution from gold mining, the EPA and the US Department of Energy's Argonne National Laboratory (ANL) have developed the Mercury Capture System (MCS), which is designed to be a simple, inexpensive, and highly effective system for capturing mercury using locally available materials.

Mercury poisoning in miners

Mercury has long been used in artisanal and small-scale gold mining (ASGM) to extract gold from ore sediment and rock deposits. This process, which involves mixing mercury with rock that contains gold, creates what is known as an amalgam. The amalgam is then heated to burn off the mercury, leaving behind the gold. However, this process releases toxic mercury vapours, which can be inhaled and pose a direct health threat to miners.

The use of mercury in gold mining has led to widespread mercury poisoning among miners, with studies indicating that up to 33% of artisanal miners suffer from moderate metallic mercury vapour intoxication. For example, a recent study found that 72% of miners at artisanal gold mining sites in Cameroon had mercury levels above the limit recommended by the World Health Organization (WHO). Mercury poisoning can cause a range of symptoms, including headaches, weakness, a bitter taste in the mouth, tremors, and coordination problems. In severe cases, it can lead to pneumonia, skin diseases, and an increased risk of miscarriage, intrauterine growth retardation, or birth defects in pregnant women. Long-term exposure to mercury can also increase the risk of developing skin, brain, or liver cancer.

Mercury is a neurotoxin that can accumulate in the food chain, particularly in fish and other aquatic organisms. It can then be ingested by larger fish and birds that eat those fish, and eventually by humans, where it can stay in the body for years. Mercury can have harmful effects on the kidneys, the nervous system, and other organs, and the neurological damage it causes can be irreversible.

The problem of mercury poisoning in miners is particularly prevalent in unregulated and unsafe mining operations, which often lack the funding and training needed to transition to mercury-free mining practices. However, there are efforts being made to reduce mercury pollution and protect miners' health. For example, the Minamata Convention on Mercury, adopted in 2013, is a global agreement aimed at controlling the mercury supply and trade, reducing mercury use and emissions, and raising public awareness about the dangers of mercury. Additionally, projects such as planetGOLD are providing technical training to miners to help them adopt mercury-free mining techniques and promote safer mining practices.

Mercury contamination in water

Mercury is a naturally occurring metal that has been extracted from the mineral cinnabar since Roman times. While it is the only metal that exists in liquid form, it is toxic to humans and ecosystems. Mercury is released through the natural weathering of rock and volcanic activity, but the main source of mercury in the environment is human activity, such as coal-combustion electrical power generation and industrial waste disposal.

Gold mining is a significant contributor to mercury pollution. In particular, "artisanal small-scale gold mines," less-industrialized facilities mostly located in developing countries, are responsible for up to 1,400 tons of mercury pollution a year, or nearly 40% of the annual total. Mercury is used in these mines to extract gold from ore sediment and rock deposits. The process involves combining mercury with gold particles in crushed rock to create a mercury-gold amalgam. The amalgam is then heated to evaporate the mercury and leave behind the gold. This releases toxic mercury vapors, which pose a direct health threat to miners who breathe the fumes.

The toxic vapors also escape into the atmosphere, where they can migrate across the world and be deposited in water bodies through rain, snow, and dry particles. Once in the water, mercury can be absorbed by tiny organisms, which are then eaten by small fish. This process of bioaccumulation results in high levels of mercury in larger, predatory fish, which are then consumed by humans. Methylmercury, a compound formed by bacterial action on ionic mercury, is of particular concern as it is far more toxic to humans and bioaccumulates to a greater extent than other forms of mercury. High levels of methylmercury have been found in fish in waters with larger sources of mercury, such as historical mining of gold or mercury within the stream's watershed.

The US Environmental Protection Agency (EPA) has developed a Mercury Capture System (MCS) to reduce mercury emissions from gold shops, which are key components of the artisanal small-scale gold mining supply chain. The MCS is designed to be inexpensive and easy to construct using locally available materials, providing an effective way to capture mercury at the emission source. By capturing and redirecting mercury for reuse, storage, or disposal, the system helps limit the release of mercury into the environment.

Gold mining in developing countries

Gold mining is a global business, with operations on every continent except Antarctica. The largest areas of gold consumption are found in impoverished developing countries. Gold mining has long been a key player in the economic development of many countries, providing employment, infrastructure, and raw materials. For centuries, developing countries have relied on their primary sectors, particularly extractive industries, as a source of wealth and economic growth.

In the past, gold mining in developing countries has been unregulated and unsafe, generating 37% of global mercury pollution (838 tons a year) – more than any other sector. Gold shops are also a key source of mercury emissions, as they are involved in the mercury trade for use in artisanal and small-scale gold mining (ASGM).

Mercury is used in ASGM to extract gold from ore, rock deposits, and sediment. The mercury binds to gold particles in ores to create amalgams, which are heated to evaporate the mercury, leaving behind gold but releasing toxic vapors. Mercury is a neurotoxin that accumulates in the food chain and is particularly harmful to species at the top of the food web, such as large predators and fish-eating birds. It can also wreak havoc on the kidneys and nervous system of humans who breathe the fumes.

However, there are efforts to reduce mercury pollution from gold mining. The US EPA and ANL have developed a Mercury Capture System (MCS) to capture mercury at the emission source and prevent it from being released into the environment. UNEP-backed projects are also empowering women in communities affected by illegal mining to pursue financial independence and safe mining practices.

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