Reducing the use of mercury in ASGM a priority

In many artisanal and small scale mining (ASGM) operations, mercury is typically used to extract gold from ore. An amalgam — a mixture of mercury and gold — is heated to recover gold, and this process induces adverse health effects and long term environmental pollution. ASGM is an important socioeconomic sector for the rural poor in many nations. While other methods to recover gold from ore have become widespread, much more needs to be done in the ASGM sector to eliminate mercury from the gold extraction process altogether.

Anthropogenic mercury release at ASGM operations contributes to the biogeochemical mercury cycle. 1 Through atmospheric circulation, elemental mercury is returned to the oceans where anaerobic bacteria in aquatic sediment produce methylmercury, which then bioaccumulates through the food chain. 2 The hazards of mercurial toxic waste have been studied extensively, and the impact of mercury bioaccumulation in living organisms is well-documented. 3

Several studies have shown how methylmercury is linked to developmental deficits. 4 Prenatal mercury exposure is adversely associated with early neurodevelopment during infancy, with decreased performance in tests of language skills and memory function. 5 Results from an exposed subgroup of infants and their mothers demonstrated this correlation through elevated levels of mercury in urine and hair tests, and this data, published in a 2020 ​paper in ​Environmental Research​, highlighted the link between the mother’s breast milk and the infant’s uptake of mercury in communities that conduct ASGM operations. 6

Another ​study on the implications of mercury exposure published in the ​Journal of Environmental Management in 2016 estimated a cost of US$77.4 million from lost annual economic productivity, which was attributed to corresponding increases in intellectual disability and lost disability-adjusted life years. 7 This economic burden, which will largely fall on developing country economies, may increase unless timely intervention of corrective measures is taken to prevent continued anthropogenic mercury contamination.

In a ​paper published in the ​International Journal of Environmental Research and Public Health​, the ASGM sector is recognised as the largest source of mercury contamination globally and is responsible for 37% of all anthropogenic mercury emissions. 8 The dangerous mercury amalgamation method is still regularly used in ASGM outfits as it is a cheap and relatively straightforward process. But mercury vapours in the air around amalgam burning sites can be alarmingly high, and almost always exceed the World Health Organization’s 1.0 μg/m3​ limit for public exposure. 9 Miners in the ASGM sector are particularly vulnerable to the effects of toxic exposure as they may have poor working conditions and lack the protective equipment to handle toxic chemicals.

Over 2,700 tonnes of gold is mined around the world annually and about twenty per cent of that is produced through ASGM operations. The elimination of mercury worldwide will undoubtedly come with a huge financial cost. In collaboration with various intergovernmental organisations and governments, a five-year US$180 million Global Environment Facility-backed programme was launched in 2019 to improve conditions for artisanal miners and aid their transition to mercury-free mining. 10 This is a laudable initiative that will support countries’ commitments under the Minamata Convention on Mercury to phase out the use of mercury in this sector.

For countries with ASGM operations, strong institutions, the adoption of enforceable mining codes, and robust regulatory frameworks are needed to prevent the proliferation of mercury usage. This will improve the health and livelihoods of vulnerable communities engaged in ASGM. The introduction of safe, mercury-free solutions into the ASGM sector, such as Clean Mining’s non-toxic gold recovery reagent, will provide a sustainable transition to job formality and dignified work for millions.

Mercury emissions impact health and ecosystems, contaminate the food we eat, the water we drink, and the air we breathe. All stakeholders will need to prioritise the reduction and eventual elimination of toxic mercury in mining, and it is clear that sustainable and clean solutions will create better returns for ASGM communities.


Clean Mining is part of the Clean Earth Technologies group.


[1] Felix Beckers and Jörg Rinklebe, “Cycling of Mercury in the Environment: Sources, Fate, and Human Health Implications: A Review,” ​Critical Reviews in Environmental Science and Technology 47, no. 9 (July 5, 2017): pp. 693-794,​.

[2] For more on the physicochemical behaviour of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms, see, Ming Ma, Hongxia Du, and Dingyong Wang, “Mercury Methylation by Anaerobic Microorganisms: A Review,” ​Critical Reviews in Environmental Science and Technology 49, no. 20 (April 16, 2019): pp. 1893-1936, ​​.

[3] Susanne M. Ullrich, Trevor W. Tanton, and Svetlana A. Abdrashitova, “Mercury in the Aquatic Environment: A Review of Factors Affecting Methylation,” ​Critical Reviews in Environmental Science and Technology 31, no. 3 (June 3, 2010): pp. 241-293, ​​.

[4] Methylmercury is a known developmental neurotoxicant. For more, see, Deborah C. Rice, Rita Schoeny, and Kate Mahaffey, “Methods and Rationale for Derivation of a Reference Dose for Methylmercury by the U.S. EPA,” ​Risk Analysis 23, no. 1 (February 19, 2003): pp. 107-115, ​​. Also see, Klara Gustin et al., “Methylmercury Exposure and Cognitive Abilities and Behavior at 10 Years of Age,” ​Environment International 102 (February 17, 2017): pp. 97-105, ​​.

[5] ​For more on the association between prenatal mercury exposure and early neurocognitive development, see, Yeni Kim et al., “Prenatal Mercury Exposure, Fish Intake and Neurocognitive Development during First Three Years of Life: Prospective Cohort Mothers and Children’s Environmental Health (MOCEH) Study,” ​Science of The Total Environment 615 (October 17, 2017): pp. 1192-1198, ​​.

[6] Stephan Bose-O’Reilly et al., “Infants and Mothers Levels of Mercury in Breast Milk, Urine and Hair, Data from an Artisanal and Small-Scale Gold Mining Area in Kadoma / Zimbabwe,” ​Environmental Research 184 (May 2020): p. 109266,​.

[7] Leonardo Trasande et al., “Economic Implications of Mercury Exposure in the Context of the Global Mercury Treaty: Hair Mercury Levels and Estimated Lost Economic Productivity in Selected Developing Countries,” ​Journal of Environmental Management​ 183 (September 2, 2016): pp. 229-235, ​​.

[8] Kyrre Sundseth et al., “Global Sources and Pathways of Mercury in the Context of Human Health,” ​International Journal of Environmental Research and Public Health​ 14, no. 1 (2017): p. 105,​.

[9] Herman Gibb and Keri Grace O’Leary, “Mercury Exposure and Health Impacts among Individuals in the Artisanal and Small-Scale Gold Mining Community: A Comprehensive Review,” ​Environmental Health Perspectives 122, no. 7 (2014): pp. 667-672, ​​.

[10] The Global Environment Facility-backed Global Opportunities for the Long-term Development of the ASGM Sector (GEF GOLD) programme is in partnership with the United Nations Development Programme, the United Nations Environment Programme, the United Nations Industrial Development Organization, Conservation International, and the governments of Burkina Faso, Colombia, Guyana, Indonesia, Kenya, Mongolia, the Philippines, and Peru. This programme will also work with the private sector across industries and partners including the Better Gold Initiative, Alliance for Responsible Mining, and Fairtrade International to promote compliance with international standards on responsible mineral supply chains.

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