Gold Mining's Dark Side: Air Pollution And Its Causes

Gold mining is a lucrative industry with operations on every continent except Antarctica. However, it is also one of the most environmentally destructive industries in the world, impacting air and water quality, ecosystems, and local communities. Air pollution is caused by the release of airborne toxins and greenhouse gases during the smelting process, as well as the hundreds of tons of mercury emitted annually. Mercury is a toxic substance used in gold extraction, and its release into the atmosphere can have severe health impacts on humans and animals.

Mercury emissions

Artisanal gold mining, in particular, has been identified as the leading source of human-caused mercury emissions. In 2011, an estimated 1400 metric tons of mercury was used by ASGM (Artisanal and Small-scale Gold Mining), with an annual average of 1000 metric tons of inorganic mercury discharged. One-third of this estimated value goes into the air, while the rest is found in tailings, soil, and waterways. Mercury emissions from gold mining operations have been found to reach hundreds of tons of airborne elemental mercury each year.

Mercury is used in the gold extraction process, and as a result, large amounts of it are released into the environment. For every 1 kg of gold produced, about 1.32 kg of mercury is lost, which goes directly into water, soil, and streams. Mercury has been detected in high concentrations in gold mine tailings, with levels as high as 1920 mg/kg reported in Kenya.

The issue of mercury emissions from gold mining is so severe that it has led to a global campaign to boycott "dirty gold." Environmental groups have asked retail companies not to sell gold produced through environmentally and socially destructive mining practices. Many of the largest jewelry retailers in the United States, including Tiffany & Co., Target, and Helzberg Diamonds, have pledged not to carry "dirty gold."

Arsenic and other toxins

Arsenic is a toxic element that is naturally present in more than 200 minerals, primarily as arsenate and arsenic sulfides, and to a lesser degree as arsenites, oxides, and elemental arsenic. Arsenopyrite, a common sulfide mineral, is often associated with gold mining. Arsenic is released into the environment through mining activities, with gold mine tailings and effluents containing high arsenic concentrations, posing risks of environmental contamination.

Gold mining, particularly artisanal and small-scale mining (ASM), frequently employs the use of mercury to capture gold. This results in the release of mercury into the soil, water, and atmosphere. Mercury emissions from gold mining contribute significantly to air pollution, with a UNEP study identifying artisanal gold mining as the leading source of human-caused mercury emissions. Mercury pollution has severe health impacts and can enter the food chain, causing adverse health effects in both humans and animals.

In addition to mercury, gold mining processes can expose workers and the surrounding environment to other toxic substances, including arsenic, cyanide, and lead. Arsenic exposure can occur through dermal contact with soil, contaminated water, or inhalation of particulate matter in the atmosphere. Studies have found elevated urine arsenic levels in miners and individuals living near gold mining areas, indicating potential future health risks. Arsenic-contaminated drinking water is a probable causative factor in elevated urine arsenic levels.

The smelting process, used to extract gold and other metals, is a significant source of arsenic emissions and other toxins. During smelting, ore is subjected to high temperatures to melt the metal and release it from other materials. Despite technological improvements, smelters continue to release toxins and significant amounts of greenhouse gases into the atmosphere.

The release of arsenic and other toxins through gold mining activities has far-reaching consequences, impacting not only the environment but also human and ecosystem health. Arsenic contamination in water, soil, and air can affect fish, vegetables, and other environmental organisms, leading to potential risks for nearby populations. The interaction between arsenic exposure and other factors, such as tobacco smoke, can further exacerbate health issues, including an increased risk of lung cancer.

Greenhouse gases

Gold mining is a significant contributor to global greenhouse gas (GHG) emissions, with the sector accounting for approximately 4-7% of total emissions. The emissions from gold mining are primarily in the form of carbon dioxide (CO2) and other toxins released during the smelting process, energy use, and ore processing.

In 2019, gold mines emitted on average 0.8-0.85 tonnes of CO2 equivalent for every ounce of gold produced. This figure, however, varies depending on the type of mining method and the region. Open-pit mines, for instance, tend to emit more GHGs than underground mines due to the larger volume of material moved and processed. On average, open-pit mines emit around 0.85 tonnes of CO2 equivalent per ounce of gold, while underground mines emit approximately 0.40 tonnes. Regional variations also exist, with Australian and Russian gold mines having higher greenhouse gas intensities compared to Canadian mines, which have a large proportion of underground mines.

The smelting process, where ore is subjected to high temperatures to extract gold, is a significant source of GHG emissions and other toxins. For example, aluminum smelters release two tonnes of carbon dioxide and 1.4 kilos of perfluorocarbons (PFCs) for every tonne of aluminum produced. PFCs are extremely potent greenhouse gases, with up to 9,200 times the heat-trapping potential of carbon dioxide, and can persist in the atmosphere for tens of thousands of years.

To reduce GHG emissions, gold mining companies are exploring clean energy substitution, energy efficiencies, and new mining technologies. By shifting to cleaner energy sources and improving energy efficiencies in ventilation and cooling, gold mines can significantly reduce their carbon footprint. Additionally, the introduction of carbon pricing can incentivize mines to reduce emissions, with the potential impact varying depending on the country and the cost passed on to producers.

While the gold mining industry has begun to set emission reduction goals, the current targets published by mining companies fall short of the Paris Agreement goals. To align with climate change mitigation targets, the industry must achieve a more substantial reduction in GHG emissions.

Health and safety risks

Metal mining, including gold mining, is one of the biggest sources of air pollution globally. Gold mining, in particular, is a significant source of mercury pollution, which has severe health implications. Mercury is used in gold extraction, and about 1.32 kg of mercury is released for every 1 kg of gold produced. This mercury goes directly into water, soil, and streams and is later converted into organic forms. Mercury can also be released into the air during the mining and roasting processes and can remain suspended in the air due to its volatile nature. When inhaled by humans, it can lead to a range of adverse health conditions.

Artisanal gold mining has been identified as the leading source of human-caused mercury emissions. The smelting of metals, including gold, is a primary source of arsenic emissions and other toxins. During smelting, the ore is subjected to very high temperatures to melt the metal and release it from other materials in the ore. While smelting technology has improved, it still releases a significant amount of toxins, including greenhouse gases. For example, aluminum smelters release two tons of carbon dioxide and 1.4 kilos of perfluorocarbons (PFCs) for every ton of aluminum produced. PFCs have a heat-trapping potential up to 9,200 times that of carbon dioxide and can remain in the atmosphere for tens of thousands of years.

Gold mining operations also contribute to air pollution through the release of hundreds of tons of airborne elemental mercury annually. The process of extracting gold from rock often involves using toxic substances like mercury and cyanide, which can pollute the air, water, and land. The use of cyanide in gold mining is particularly concerning, as it is enormously wasteful and creates immense, toxic piles of waste that can reach heights of 100 meters. These toxic piles are often abandoned, leading to contaminated water and soil, which can poison nearby communities.

Additionally, gold mining activities can generate large quantities of heavy metal-laden wastes, which, when released uncontrolled, cause widespread contamination of the ecosystem. Higher concentrations of heavy metals above stipulated levels can have detrimental effects on human health and the environment. The chemicals used in processing gold can also contaminate the air, water, and soil. For example, an estimated 1,000 metric tons of inorganic mercury were discharged annually, with one-third going into the air and the rest mixing with tailings, soil, and waterways.

Mercury in the food chain

Mercury is a potent neurotoxin that can cause irreversible neurological damage, kidney damage, and impaired cognitive function. Inhalation of mercury vapour is a common issue for miners, but mercury can also enter the food chain, causing widespread harm to human and animal health.

Mercury is used in artisanal and small-scale gold mining (ASGM) to extract gold from ore as an amalgam. The amalgam is then heated to vaporize the mercury and isolate the gold. This process releases mercury into the environment, where it can contaminate water and soil. ASGM is the largest source of mercury pollution on Earth, with an estimated 10 to 19 million miners using mercury in more than 70 countries.

Fish are a major source of dietary protein in many ASGM regions, and mercury contamination in fish is a significant concern. Mercury accumulates in fish and other food supplies in ASGM communities, leading to increased exposure and health risks for those who consume them. The risks are particularly high for children, who are more susceptible to the harmful effects of mercury, including physical deformities, neurological damage, and lower IQ.

Methylmercury, a highly toxic form of mercury, can be produced through a complex biogeochemical process involving the oxidation of elemental mercury and subsequent methylation. This process is influenced by various environmental factors, including temperature, dissolved organic carbon, salinity, and acidity. Methylmercury can be absorbed by plants and enter the food chain, posing risks to human health. Efforts to prevent mercury uptake in fish and food crops are crucial to mitigating the impact of mercury pollution on the food chain.

The impact of mercury pollution from gold mining on the food chain is a global issue that requires international cooperation and the development of low-cost, adaptable solutions suitable for remote and under-resourced areas where ASGM is prevalent. Political motivations, such as the Minamata Convention on Mercury, provide an opportunity to address this growing crisis and protect human and environmental health.

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