Gold mining’s connection to the mercury trade

Mercury is used in the artisanal and small-scale gold mining (ASGM) sector to extract gold from ore, and ASGM operations are the predominant source of anthropogenic mercury pollution in the world. Numerous countries and inter-governmental organisations have acted to limit the use of mercury worldwide, but much more needs to be done to completely eliminate this toxic, silvery liquid from the gold supply chain.

Gold has seen an astronomical rise in value by about 500 per cent over the last twenty years, to approximately USD1,900 at present. 1 This has led to increased artisanal mining activity, which often takes place in regions with vulnerable populations that experience geopolitical instability, high levels of poverty, and elevated incidences of social precarity. Providing sustenance to 190 million people directly and indirectly, the ASGM sector is responsible for at least 20% of global gold production. 2 However, ASGM activities release about 1,000 tonnes of anthropogenic mercury emissions, or about 40 per cent of global mercury emissions every year. 3

Artisanal gold miners often use the process of mercury gilding to form a mercury-gold amalgam. When the amalgam has a consistency similar to that of butter, it is then heated to extract the gold. 4 But through this process, roughly one to two grams of vaporised mercury is lost to the environment for every gram of gold produced, and this has an incredibly negative impact on miners, their surrounding communities, and the environment.

Volatilised mercury contaminates the air, soil, and waterways. Numerous ASGM operators have contaminated their surrounding environment, and the results have been widely documented. A study conducted in Colombia revealed the presence of mercury in water bodies at the Grande Achi and Ayapel marshes, which are in close proximity to sites with extensive ASGM operations. Elemental mercury found in Grande Achi was directly attributed to mercury released from the volatilisation of mercury, and higher-than-normal percentages of other labile mercury species in both marshes were also observed. 5 Another study into the distribution of mercury in the soil, sediment and river water near an artisanal and small-scale gold mining in Indonesia found the Cikaniki River to be extensively contaminated, with total mercury concentration in the surrounding forest soil ranging from 0.11 to 7.0 mg kg-1. 6

Microscopic organisms in the soil and water can convert elemental and inorganic mercury compounds into an organic mercury compound, methylmercury, which bioaccumulates in fish and biomagnifies up the aquatic ecosystem. In Ghana, 54 per cent of water samples recorded near active ASGM sites were rated unsafe for aquatic life and general consumption due to mercury contamination. 7 In Bolivia, mercury that leached from high altitude ASGM sites resulted in the uptake of mercury in livestock. 8 Downstream water bodies near two mining sites in Buru Island, Indonesia, contained mercury-contaminated fish, posing a threat to nearby fisheries and food safety for the surrounding communities. 9 When humans catch and consume mercury-contaminated fish, exposure to this potent neurotoxin may damage one’s central nervous systems and cause a wide range of long-term health complications.

In a 2017 paper published in Ecotoxicology and Environmental Safety, researchers found that residents in China’s Tongguan Village, which had a long history of artisanal mining, had chronic conditions associated with their inadvertent intake of mercury-contaminated products. 10 In neighbouring Mongolia, an environmental epidemiological study discovered that residents not involved in artisanal mining but living in areas surrounding mining operations also displayed high levels of mercury. Public health support measures are therefore urgently needed to alleviate the burden of environmental mercury contamination, and this is primarily because communities living near ASGM operations are at demonstrably higher risk of adverse health effects arising from mercury poisoning.11

Recognising the horrific implications of mercury contamination, many countries have imposed bans on the trade of mercury. But this has had the unfortunate effect of propping up the black market trade of mercury. For countries to effectively stamp out the illicit trade of mercury, legislation must be adopted to formalise the ASGM sector as this will allow enforcement mechanisms that require artisanal outfits to utilise non-toxic alternatives, such as Clean Mining’s gold recovery reagent. 12

To limit the loss of volatilised mercury to the environment, some inter-governmental organisations have suggested using a retort at ASGM operations to reduce mercury emissions by up to 95 per cent. 13 However, there is no safe limit to mercury exposure, and mercury pollution will still occur when using a retort. The full elimination of mercury from the gold supply chain is necessary, and this can be accomplished in an economical and sustainable manner. 14 Clean Mining’s gold recovery reagent is scalable to suit various operations, and mining operators will also be able to reduce their mining footprint. When ASGM operators have a cost-effective, non-toxic, and mercury-free way to recover gold, this will inevitably strip demand for the dangerous silvery liquid, and there will be long-standing positive effects for artisanal miners, nearby communities, and the environment.

There is little doubt that the issues surrounding mercury contamination by ASGM operators are complex and multi-dimensional. But the solutions to rid the world of ASGM-attributed anthropogenic mercury pollution will require numerous stakeholders to address crucial considerations, promulgate policies and strategies, and advocate for the promotion of sustainable technologies that will lead to sector-wide improvements. Mercury pollution from the ASGM sector is a widespread problem that needs to be highlighted, and the nature of transboundary mercury contamination recorded in various jurisdictions show that it is a regional and global issue that needs to be tackled with urgency.

For the gold mining industry, the connection to the illicit mercury trade is one that needs to be severed. Nothing comes quite as close to gold as a store of value because there is no equivalent fungible asset type that matches its qualities of unimpeachable rarity, liquidity, and portability. And for that exact reason, nothing, and especially not mercury, should tarnish the purity of gold.


Clean Mining is part of the Clean Earth Technologies group.


[1] For more on gold prices through the years, see, “Gold Price Historical Data: Gold Price History,” World Gold Council, November 2, 1970,

[2] For more ASGM statistics, see, “$180 Million Investment to Tackle the Hidden Cost of Gold,” December 23, 2019,​.

[3] Carlos Salazar-Camacho et al., “Dietary Human Exposure to Mercury in Two Artisanal Small-Scale Gold Mining Communities of Northwestern Colombia,” Dietary human exposure to mercury in two artisanal small-scale gold mining communities of northwestern Colombia (Environment International, 2017),

[4] See, for more on the mercury amalgamation process, Jesper Bosse Jønsson, Elias Charles, and Per Kalvig, “Toxic Mercury versus Appropriate Technology: Artisanal Gold Miners’ Retort Aversion,” Resources Policy 38, no. 1 (2013): pp. 60-67,

[5] For more on the percentages of mercury species in the marshes, see, José Marrugo-Negrete, José Pinedo-Hernández, and Sergi Díez, “Geochemistry of Mercury in Tropical Swamps Impacted by Gold Mining,” Chemosphere 134 (2015): pp. 44-51,

[6] See, for more on the mercury concentration in the Cikaniki River, Takashi Tomiyasu et al., “The Distribution of Mercury around the Small-Scale Gold Mining Area along the Cikaniki River, Bogor, Indonesia,” Environmental Research 125 (2013): pp. 12-19,

[7] For more on the impact of mercury on water samples in Ghana, see, Martin J. Clifford, “Assessing Releases of Mercury from Small-Scale Gold Mining Sites in Ghana,” The Extractive Industries and Society 4, no. 3 (2017): pp. 497-505,

[8] See, for more on the impact of mercury in Bolivia, Tania A. Terán-Mita et al., “High Altitude Artisanal Small-Scale Gold Mines Are Hot Spots for Mercury in Soils and Plants,” Environmental Pollution 173 (2013): pp. 103-109,

[9] The water pollution in Buru Island might also reduce food safety and affect the business of fisheries. For more on the impact of mercury in Indonesia, see, Amanda J. Reichelt-Brushett et al., “Geochemistry and Mercury Contamination in Receiving Environments of Artisanal Mining Wastes and Identified Concerns for Food Safety,” Environmental Research 152 (2017): pp. 407-418,

[10] For more on inhalation risks on the villagers in Tongguan, China, see, Ran Xiao et al., “Soil Heavy Metal Contamination and Health Risks Associated with Artisanal Gold Mining in Tongguan, Shaanxi, China,” Ecotoxicology and Environmental Safety 141 (2017): pp. 17-24,

[11] For more on mercury levels on both miners and residents in Mongolia and their health effects, see, Nadine Steckling et al., “Mercury Exposure in Female Artisanal Small-Scale Gold Miners (ASGM) in Mongolia: An Analysis of Human Biomonitoring (HBM) Data from 2008,” Science of The Total Environment 409, no. 5 (January 2011): pp. 994-1000,

[12] Alongside technological advancements, regulatory frameworks put in place can support the adoption of viable solutions. Launched in 2019 under the Minamata Convention on Mercury, the five-year Global Environment Facility-backed programme spans over eight countries to support the uptake of mercury-free extraction methods, provide the necessary financial access, and ensure optimal working conditions for artisanal miners. To go hand-in-hand with these “traditional” approaches for pollution, information-based strategies can be promoted to educate the various stakeholders on the risks and increase advocacy for improvements in the ASGM sector. For more on the various solutions posited to reduce mercury pollution, see, Rebecca Adler Miserendino et al., “Challenges to Measuring, Monitoring, and Addressing the Cumulative Impacts of Artisanal and Small-Scale Gold Mining in Ecuador,” Resources Policy 38, no. 4 (2013): pp. 713-722,

[13] For more on the retort solution, see, Jesper Bosse Jønsson, Elias Charles, and Per Kalvig, “Toxic Mercury versus Appropriate Technology: Artisanal Gold Miners’ Retort Aversion,” Resources Policy 38, no. 1 (2013): pp. 60-67,

[14] See, for more on the proposed requirements of a non-mercury gold extraction technique, Louisa J. Esdaile and Justin M. Chalker, “The Mercury Problem in Artisanal and Small-Scale Gold Mining,” Chemistry – A European Journal 24, no. 27 (May 2018): pp. 6905-6916,

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