Four Decades of Efforts to Reduce or Eliminate Mercury Pollution in Artisanal Gold Mining

Abstract

Throughout the past four decades, most projects related to mercury in Artisanal Gold Mining (AGM) have been dedicated to monitoring the environmental and health impacts of the activity without actually proposing effective solutions to tackle the issue. Recently, the UN and a few NGOs have been dedicated to bringing solutions to artisanal gold miners, but the outcomes remain modest, given the funds expended and the considerable effort invested by interventionists. This commentary paper critiques some of the interventions observed in the last four decades and suggests some technical strategies to approach artisanal miners to reduce mercury losses. It is stressed that mercury elimination is a consequence of good engagement with miners that creates opportunities to show them how to produce more gold with cleaner methods. We recommend that academics educate a new generation of engineers working with AGM to adopt a more practical approach, ensuring they understand the needs, motivations, and skills of artisanal miners before proposing solutions.

1. More Mercury Monitoring, Less Solutions Applied

The mercury problem in Artisanal Gold Mining (AGM) was first raised in Brazil in 1981 when the Brazilian Ministry of Environment established a small project with CETEM (National Center for Mineral Technology, Rio de Janeiro) to monitor and suggest solutions to reduce mercury pollution in an AGM site. The project finished without any interventions to reduce mercury use, as all funds were spent on analyzing mercury in water, fish, humans, etc. In 1982, Dr. Jacques Cousteau, in an expedition to Serra Pelada, an iconic Brazilian AGM site, highlighted in the Press the dangers of mercury methylation and bioaccumulation in Amazonian fish [1]. Serra Pelada was an AGM site in the Brazilian Amazon, where, in the 1980s, 80,000 artisanal miners were mining gold ores and processing with rudimentary gravity concentration processes and amalgamating the concentrate [2,3]. A series of academic research started, headed mainly by Dr. Wolfgang Pfeiffer from the Biophysics Institute of the Federal University of Rio de Janeiro and then by a research group at the Federal University of Pará (in the Amazon region) and the National Mineral Production Department (DNPM), also in Pará State. Most studies were focused on the possibility of mercury from artisanal miners being methylated. A very good retrospective of the investigations of mercury in the Amazon was brought by Dr. Jean Guimarães (2020) [4], with details of each protagonist in studying mercury in the region.

From 1989 to 1992, CETEM started a project sponsored by the Brazilian Congress in Poconé, a city near the Ecological Park of Pantanal, where artisanal miners dumped tailings into a small lagoon that lost its recreational function. Thanks to the action of the hydrous ferric oxides in the ore, which adsorbed any possible oxidized mercury coming from the artisanal gold miners [5,6], no significant mercury pollution (fish bioaccumulation) or mobilization was detected. With the popularization of the Internet, more information revealed the mercury problem in AGM operations in African, Latin American, and Asian countries. From 1995 to 1997, UNIDO (United Nations Industrial Development Organization) started missions to Venezuela, Suriname, and Guyana to understand the gold rushes in Latin America [7]. In the 1990s, the theme of AGM was not very popular in universities, international agencies, NGOs, and governments, even in developing countries, where the problem was escalating due to the increase in the gold price. A small group of researchers in Brazil, Canada, and England was prominent in publicizing mercury’s environmental and health effects on artisanal miners and their communities in developing countries. Despite the dire need to stop the flow of mercury to AGM sites, the objective of the projects was to monitor fish and humans, with the justification that it was important to justify the problems to provide solutions.

The projects and media concentrated on showing the mercury impacts on humans and the environment, pointing fingers at the increasing contingent of poor people who became artisanal miners to escape social marginalization in developing countries. The Press’s tone of the moment was “Stop all artisanal mining activities”. This motto, however, represented a utopian perspective on the solution, particularly in the absence of enforcement, training, clear regulations, and a clear understanding of the socioeconomic factors related to AGM. A small group of engineers working on solutions to the problem often remarked that, rather than addressing the underlying issue, efforts were being disproportionately directed toward assessing its consequences. When witnessing many environmental projects and scientists traveling to AGM sites, an artisanal miner in Africa once said, “It seems that more people are living from mercury than dying from mercury”. This criticism highlighted that the environmental and health approaches outnumber the solutions brought to the AGM and have never influenced miners to stop their polluting activities.

The saga of mercury monitoring without knowing the sources or providing solutions was intensified in the next millennium. Certain studies appeared opportunistically designed to examine mercury and methylmercury levels in the hair and blood of indigenous populations, whose sole source of protein is fish. These studies suggest that AGM contaminates all aquatic biota within a region, urging local inhabitants to refrain from consuming these fish. Sometimes, fish have low to medium levels of mercury compared to the international guidelines, but the intensity of consumption was revealed in the high levels of mercury in the natives’ hair.

Nutrition scientists, attempting to advance solutions to the high preference of the local people for the consumption of carnivorous species of fish, which are often more contaminated with a higher level of methylmercury, advocated for eating other types of fish than the carnivorous (tastier) ones, changing cooking recipes, and eating a more balanced diet as possible solutions. Milea et al. (2023) [8] highlighted that eating fish with garlic and broccoli decreases mercury bioavailability. In lab studies, Ouedraogo and Amyot (2011) [9] found that coffee and teas (polyphenol-rich beverages) significantly reduced fish Hg bioaccessibility by 50%–60%.Jovel et al. (2018) [10], in a lab study, demonstrated that select vegetables, such as garlic, kale, broccoli, cauliflower, and cabbage (rich in thiol radicals) showed good potential for Hg (II)-binding activity, which could be applied as a chelation technique to individuals contaminated with mercury from vapor exposure. Mieiro et al. (2016) [11] observed in lab studies that organic mercury decreases when fish is cooked. This was also confirmed by Girard et al. (2018) [12], who found that cooked fish decreases in vitro methylmercury bioaccessibility by 12.5% compared with raw fish. The ingestion of selenium-rich foods, like Brazil nuts, can also positively reduce the bioaccessibility of mercury in the organism [13]. Passos et al. (2003) [14], in an excellent study, tried to convince Amazonian women to eat more fruits to reduce the levels of methylmercury in their bodies. Sometimes, the solution is to add other types of food to the diet to dilute the amount of fish ingestion, but this is not always possible in impoverished riverine communities. Changing the food habits of local inhabitants is challenging and culturally complicated, but it appears to be the only solution, particularly for women of childbearing age and children. As Dr. José Dórea (2010) [15] mentioned, “…subsistence populations of the Amazon often do not have the choice of giving up fish”.

Mercury monitoring projects are important in revealing the priorities for interventions that are rarely implemented or sustained. Many individuals at AGM sites are used as test subjects to donate hair, blood, urine, nails, umbilical cords, and maternal milk for mercury analyses, and frequently, they do not receive the analytical results.

2. Where Does the Mercury Come from?

Typical information in scientific papers and the Press, particularly in the Amazon, is that fish are contaminated with mercury from AGM alone. This seems like a quick conclusion, as the mercury used by AGM is the only visible one, but there are many sources of mercury pollution in the atmosphere. Many places in the Amazon are distant (700 to 1000 km) from AGM operations, yet they have fish contaminated with mercury. This relates to the environmental chemistry of rivers [16]. Soils at river margins are relatively rich in mercury, which has been deposited over millions of years from various sources and can potentially contribute to mercury release into the aquatic environment when soils are eroded [17]. The role of dissolved organic acids, which give the dark color of some Amazonian streams, is of paramount importance in the complexation of oxidized mercury, which is conducive to methylation [18,19,20,21]. Organic acids in solution form much more stable complexes with mercury than inorganic species, and these acids can remove mercury adsorbed on the suspended sediments [22]. The transformation of metallic mercury into methylmercury, which rapidly accumulates in aquatic biota, is a multifaceted process that requires metal oxidation, complexation with organic acids, and bacterial methylation, mainly in anaerobic environments. Atmospheric mercury from volcanism, forest fires, evaporation, the erosion of riverbanks, the weathering of various geological components, and the deterioration of submerged vegetation deposited for thousands of years in soils may be relevant sources of mercury in the Amazon. Data from experts [23] revealed that, globally, natural sources of mercury emissions (volcanoes, evaporation, forest fires, soil erosion, etc.) (to the atmosphere) range from 6500 to 8200 t/a (56% to 82%) and human sources range from 1900 to 2900 t/a (18% to 44%). Recently dispersed industrial sources (including artisanal mining) are also important in the bioaccumulation of mercury in fish, but it is necessary to reveal all the “villains”.

A recent technique using stable isotopes of mercury can elucidate the origin of mercury in sediments [24]. In areas where Ecuadorian artisanal miners use the cyanidation of mercury-contaminated tailings, isotopic analysis showed that tailings from Processing Centers with soluble mercury cyanide complexes that were discharged into the Puyango River reached 160 km downstream in Peru [25]. This analytical technique also offers the opportunity to understand the origin of methylated mercury in fish muscles [26,27]. Today, we know that the biological and thermodynamic conditions of the aquatic environment are more important factors for the formation of methylmercury than the concentration of mercury in the substrate (soil or aquatic sediment). The high concentration of metallic mercury in sediments does not always correlate with the high methylation rates observed. For example, in the artisanal mining area in the municipality of Cachoeira do Piriá, State of Pará, fish in areas extremely polluted with mercury-rich mining tailings showed lower methylmercury levels than fish in unpolluted areas but rich in organic matter [28,29]. Differentiating the natural sources of mercury pollution from anthropogenic ones has been a challenge that isotopic analysis tries to solve. This does not exonerate artisanal miners and their rudimentary practices, but it puts into context that not all published pollution has a single origin.

It is interesting to notice that mercury vapor released when amalgams are burned in open air or when gold doré (retorted but still with residual Hg) is melted in gold shops in urban areas has received little attention when this is the main imminent problem for miners and surrounding communities [30,31]. The dissemination of filters and retorts to condense mercury vapors, preventing them from spreading throughout the environment, has been seen by some governments as a subversive action in countries where the use of Hg in AGM is prohibited. Professor Raphael Hypolito from the University of São Paulo was a target of legal demands because he promoted homemade retorts built with water pipes [32]. Dr. Adam Kiefer from Mercer University devised an amazing system to capture mercury vapors during amalgam decomposition. This uses induction to evaporate mercury that is sucked from below [33]. However, Dr. Kiefer said that “…the system is not being sold anywhere as the liability is too high”. In countries where mercury is illegal to be used in AGM, the promotion of any vapor abatement process is seen by authorities as a way to produce mercury. Nowadays, the “subversive engineering solution” actions are being disseminated and saving the lives of miners and community members [34,35]. Homemade retorts are a good way to engage with miners as they see that they can fabricate their own personal protective equipment and save some money by reusing the retorted mercury.

3. No Data on Mercury, No Pollution

Today, almost 20 million artisanal gold miners (probably half of the contingent of all types of artisanal miners in the world) produce 15%–20% of gold, bringing economic benefits to more than 100 million people in 80 countries [36,37]. The UNEP Global Mercury Assessment (2018) estimated that 2220 t/a of mercury is emitted by anthropogenic sources to the atmosphere, of which 838 t/a comes from AGM. With an additional 1220 t/a of mercury in tailings discharged by AGM, this adds up to 2058 t of mercury going to the environment. According to UNEP, this sector is the world’s highest source of mercury contamination. All these estimates were obtained by using a mixture of guesswork and calculations [38] with very little field inventory to confirm the quantification of mercury losses. The estimates of mercury emissions and releases were usually obtained by UN COMTRADE (a UN global trade data platform), which assesses the amount of mercury officially traded by countries associated with information about AGM gold production. The UN Minamata Convention, established in 2013, intends to incentivize governments to curb mercury trade, but despite all the good intentions of the Convention, mercury commerce was intensified by smugglers. Even well-established groups of Canadian mercury researchers encountered challenging and uncomfortable situations upon witnessing instances where individuals or entities within the country were involved in exporting substantial quantities of mercury—ranging from tens to hundreds of tonnes—to Cuba, with its final destination remaining uncertain [39]. At the mining sites, the price of mercury tripled after the Minamata Convention came into effect on 16 August 2017. On the Internet, it is possible to observe that mercury sales are still openly promoted in many sites. However, developing countries no longer reveal the official quantities of mercury imported.

How can one assess the increase and decrease in mercury use and losses in AGM sites when official numbers of mercury imports are not available? The UN COMTRADE numbers show levels close to zero of mercury importation by countries with hundreds of thousands of artisanal gold miners. Some politicians may highlight the success of enforcement actions against artisanal miners by referencing these UN statistics as evidence of their effectiveness. However, the reality is different in the field, with mercury being freely sold and used. Field evaluations of mercury losses must be obtained with an exhaustive sampling of the amalgamation operations to obtain actual numbers and not only guesstimates [40,41,42]. The mercury “use” reported by the countries’ NAPs (National Action Plans), outlined by Keane et al. (2023) [43], can bring confusion to the estimates once the mercury added to an amalgamation operation is not necessarily the amount lost, as usually 50% of mercury added is recycled when excess mercury is squeezed off from the amalgam. Projects in AGM sites rarely apply metallurgical balances to quantify mercury losses in the field.

4. Engineering Solutions Are Overlooked

The number of projects introducing cleaner techniques in AGM compared with mercury monitoring projects is disproportional. Even good researchers, like Jean Guimarães (2020), [4], overlooked the role of engineers when he said, “At this point, the reader who is not familiar with Hg may have realized that tackling environmental Hg issues with a minimum of effectiveness requires the participation of several disciplines, of which the most obvious so far are chemistry, analytical chemistry, atmospheric sciences, hydrology, microbiology, ecology, and toxicology. If human exposure is a concern, add health and social sciences such as sociology and/or anthropology to the discipline basket”.

From 2002 to 2007, GEF/UNDP/UNIDO conducted the Global Mercury Project (GMP) to introduce methods to reduce or eliminate mercury pollution from AGM. The initial 2.5 years were dedicated to environmental and health monitoring in Brazil, Indonesia, Laos, Sudan, Tanzania, and Zimbabwe, focusing on demonstrating to the politicians of these countries the evident health impacts when miners (in particular women and children) burn amalgams in a bonfire with his/her noses close to the amalgam (Figure 1). The GMP was the first international step towards the effort to understand the social and biophysical implications of AGM, generating interventions and primarily teaching almost 30,000 miners and their community members how to operate a cleaner gold processing plant [44]. The participation of miners in the project was crucial to understanding that they must tell us if they are willing to reduce mercury use. This was an important lesson for all interventionists, who must learn that any project to eliminate mercury usage must start by asking miners what their NEEDS are, what their MOTIVATIONS are to keep processing in a polluting way, and what SKILLS they already have to learn new methods [45]. The economic factor (better gold production) must be the main one to highlight to artisanal miners. They are suspicious of the list of environmental and health impacts brought up by interventionists. Some miners believe interventionists are trying to steal their gold deposits.

It is observed that many projects bring a specific process to extract gold that AGM must use without even knowing what the current % of gold extraction is. Most interventions in AGM suggest using gravity separation equipment to replace whole ore amalgamation, which is very commendable. Gravity concentration is not a panacea as it depends on the mineralogy of the ore [46]. Worldwide, over 300 conventional gold mining companies are listed (each with more than one mine), and the majority of mines work with primary ores with higher gold grades than secondary weathered ores. For the latter, tens of thousands of tons of ore are processed daily to justify the investment. Conventional mines remove medium to coarse gold by gravity concentration (centrifuges) before the flotation and/or cyanidation. They typically extract 20%–30% of gold by gravity and the rest by cyanidation. Given this established practice, one may question why the process would differ in AGM. Although gravity concentration presents certain challenges, it is often perceived as a more accessible and cost-effective option for artisanal miners compared to promoting flotation, cyanidation, or other leaching processes. There are ways to increase gold recovery using only gravity concentration [47], but one solution does not fit all cases.

Before suggesting any gravity equipment to artisanal miners, it is important to know the % of gold recovery they currently have. Artisanal miners must understand that the % of gold recovery is not the amount of gold they put in their pockets, and the systematic sampling of feeds and tailings with analytical support must engage miners in the whole process. The AGM’s % of gold recoveries are usually very low when they use sluice boxes and amalgamate concentrates or even when amalgamating the whole ore. Lab results show that whole ore amalgamation of a non-refractory ore from a Colombian AGM site resulted in less than 19% of gold recovery when cyanidation extracted 84% [48].

When a concentrate was obtained using rudimentary gold sluices and manually amalgamated, the gold recovery in many cases (Brazil, Suriname, Nigeria, and Colombia) was found to be close to 20%–40%. A sound sampling with chemical analyses of the concentration and amalgamation plants used by miners will show miners that they lose 70 to over 80% of gold when they process the ore [42]. Unfortunately, gold metallurgical balance is not a common practice in projects that bring a pre-established solution for miners. It is, therefore, not surprising that the solutions are not always durable, as miners often revert to their polluting methods when they do not have the “expert” around, as observed by [49].

Another important piece of information is to know in which grain size fraction the gold is lost in the existing gravity circuit used by the miners. Grain size analyses of the tailings help find out whether gold is lost in the coarse fractions (unliberated) or the fines (fine gold particles not necessarily liberated) [47]. Many miners believe that gold is mainly lost in fine grain sizes, but in most cases, the main gold losses occur in the coarse grain size fractions associated with the gangue minerals. Then, the interventionist must come up with methods to liberate, or partially liberate, gold specks from the coarse fraction minerals before concentration. Therefore, the primary strategy and first step to introducing mercury-free techniques is establishing suitable grinding methods (e.g., scrubbers, Chilean mills, small ball mills, etc.). The second step is to select the appropriate equipment to concentrate coarse, medium, and fine particles of gold. As gold in alluvial ores is frequently liberated, interventionists, unfamiliar with mineral processing, do not pay attention to studying gold liberation before suggesting equipment. Concentration is the primary way to reduce mercury use and loss. Whole ore amalgamation is the main reason for high levels of mercury loss [50]. However, the concentration equipment must be carefully selected, observing the regional availability, the water and power supply, the miners’ skills, the maintenance availability, and most importantly, the mineralogical characteristics of the ore. Where is the gold in the ore? Associated with what? Which minerals? Fine gold? These are some questions that must be answered before establishing a processing plant. It is important to understand the symptoms when selecting medicine, like a medical doctor. The lack of information about the mineralogy of the ore can cause disastrous situations. In 2010, artisanal miners in Zamara State in Nigeria overlooked the presence of galena (PbS) in the gold ore. They dry-ground the ore, releasing lead-laden dust particles into the environment. This had a detrimental impact on various miners and culminated in the tragic loss of more than 400 children living around the processing plants [51]. This and other events of the intoxication of operators and community members by mercury vapors and other harmful substances are widely reported in the scientific literature [31]. Some good articles on health monitoring claim solutions [52], but many do not even know what solution must be applied.

Using a Multicriteria Decision Analysis tool, Morgan et al. (2021) [53] determined the rank of alternatives to reduce mercury exposure based on publications about AGM. They concluded that the Borax Method has 72% of the attention of the “interventionists”. This reflects the low understanding of mineral processing and metallurgy of those implementing solutions for mercury elimination. The smelting of gold concentrates with borax is proper for yellow concentrates with at least 3% gold and no sulfides [54]. The proponents of this method appear to be unaware of a fundamental principle in mineral processing: “The more you concentrate, the more you lose” [47]. The gold grade increases, but the gold recovery decreases. How do we justify a miner losing 90% of the gold to obtain such a rich gold grade in a concentrate? This approach works with alluvial ores, which are not the principal source of mercury pollution in AGM worldwide, as gold is usually liberated, and it is easy to obtain a rich yellow concentrate by panning. This has been used for centuries by alluvial North American miners, but it is not totally applicable to all types of ores [34].

Disregarding the knowledge and expertise of both contemporary and traditional artisanal miners in the implementation of interventions has led to significant challenges. An effective engagement process is essential, as interventionists must establish trust with miners and actively involve them in consultations before introducing any changes to their established practices.

Interestingly, the only method to eliminate mercury currently seen in countries with AGM is the co-existence between artisanal miners and conventional companies [31]. This aspect is rarely discussed in the scientific literature or actively promoted by governments. Artisanal miners extract the ore within their mineral titles or within a designated company’s area if they have obtained their consent. Subsequently, they transport the ore to a responsible processing company that employs appropriate engineering procedures to extract over 90% of the gold contained in the ore. After sampling and chemical analyses, the companies pay the miners 50% or more of the gold content in the ore instead of less than the 30% the artisanal miners would have obtained with primitive sluices and amalgamation. At least 25 companies in Latin America are adopting this process. The company responsible for the mineral claims allows artisanal miners to extract ore in their titles and provides technical and legal assistance [55]. This eliminates the use of mercury [56].

Formalization is a solution that many scholars promote [57,58,59], but they recognize that it is hard to find mineralized deposits not taken by conventional mines. The lack of available areas is indeed the main hurdle for a formalization process [31]. In addition, some formalized processing facilities still contaminate the environment and operators with mercury and cyanide [60]. Without effective enforcement, legal miners assert that their formalized status allows them to operate without constraints. The difference between formalization and legalization must be understood [61]. The formalization involves legal status plus the implementation of best practices, which goes beyond the legalization process of providing permits [31,62]. The formalization process must follow an order: (1) organization of the miners, (2) training and education, (3) legalization, and (4) formalization. This order cannot be different; otherwise, the system legalizes pollution. The establishment of Permanent Training Centers for Artisanal Miners (TCAM) has been advocated by some scholars for years; however, governments frequently regard the legalization of AGM as the sole key strategy to eliminate mercury. It is impossible to formalize miners if they are not educated. A TCAM can provide miners with technical, legal, environmental, and social assistance [45,60,63].

5. A Herculean Effort

Many agencies have spent a significant amount of money on studies of mercury in AGM. In the last four decades, international donors and implementing agencies, universities, and NGOs have probably spent around USD 1 billion, but again, not all of them have approached sustainable technical solutions.

Assessing the Global Environment Facility (GEF) (2025) Project Database using the keywords “Artisanal and Small-scale mining” and “Gold from 1970 to 2024, we found 85 projects in many different developing countries in which USD 340,442,001 was invested by the GEF. The co-financing of USD 1.83 billion from the developing countries’ governments is likely only as in-kind contributions to justify the time spent by their local project implementers. In the list, there are 32 projects with mercury in their titles. In 1970, about USD 116 million were invested in four projects: (1) Senegal; (2) Costa Rica; (3) Bolivia, Congo, Ghana, Honduras, Madagascar, Nigeria, Suriname, Uganda, Cote d’Ivoire, Ecuador, Guinea, Mali, Nicaragua, Sierra Leone, and Zambia; and (4) Burkina Faso, Colombia, Guyana, Indonesia, Kenya, Mongolia, Peru, and Philippines. Information about the results of these projects is not clearly documented and is hard to find on the Internet.

After 1970, it was only in 2002 that the GEF started to reinvest in AGM projects. PlanetGold’s actions in 26 countries plan to reduce 63% of mercury losses (or 494 tons) by 2025 [64]. The implementers of the projects are UN agencies, and the executers are usually international NGOs, with some using professionals with experience, others learning and improvising; however, at least the idea of bringing solutions to stop mercury pollution is on the mind of all project participants. PlanetGold (2024) [65] reported the program’s activities in 2022–2023. The report mentioned that 0.4 t of mercury was eliminated from the AGM plants (Hg-free techniques introduced), 1.4 t was reduced, meaning that less mercury is being introduced in the amalgamation process, and 29.6 t of mercury was prevented (according to PlanetGold (2024) [65]: “The amount of mercury loss to the environment that is assumed to be prevented by the introduction or ongoing support of mercury-free methods”), i.e., not entering the process. This is a fantastic effort; however, it is unclear in the report whether the % of gold recovery increased with the mercury reduction or elimination at the intervened sites. In any case, the sustainability of the projects is questionable as governments are usually not entirely engaged and do not have the technical people to continue with the actions they learned. Governments in developing countries are becoming excessively reliant on foreign projects to address the mercury problem. It is uncommon to observe any measures executed by local governments utilizing their own financial and human resources.

Notwithstanding the ongoing efforts evidenced by certain publicly funded initiatives in Nigeria, a notable deficiency persists in the acquisition of essential data concerning the mineralogical characteristics of the ore and the prevailing local economic conditions. Such data would considerably enhance informed decision-making regarding critical parameters, including the selection of appropriate mineral processing methodologies and equipment types. For instance, the state launched a project aimed at employing the IGoli method [66] for the processing of gold ore in Zamfara State. Regrettably, the initiative yielded minimal outcomes owing to insufficient acceptance and support from the miners. The gold processing facility recently established by the State has remained inoperative and in a condition of disrepair since its inception. The lack of progress in the project may be closely associated with the insufficient acknowledgment of the insights provided by Keane et al. (2023) and Esdaile and Chalker (2018) [36,43]. These scholars also underscore the necessity for interventionists to evaluate the appropriateness of any mercury-free technologies through a comprehensive assessment of various factors, including the improvement of % gold recovery, characteristics of the ore, operational requirements, workflow and technological performance, local technical considerations, skills of the miners, and health, safety, and environmental concerns.

It seems idealistic to believe that any mercury-free technique to bring to miners’ attention will extract high levels of gold only with gravity methods without a hydrometallurgical process [46]. This can be achieved for alluvial ores, but when processing other types of ores, conventional mining companies always use cyanidation to extract the fine exposed particles of gold not captured by gravity equipment. In fact, most gold in the world is produced by leaching with cyanide. Some Processing Centers, with poor knowledge of cyanidation chemistry, use this leaching process to extract parts of gold from an ore or tailing.

An important criticism of the interventions is that most projects do not deal with the main mercury polluters in AGM, the Processing Centers. In most developing countries, artisanal miners do not have their own processing facilities. They transport their ores to private processing plants, where gold extraction is conducted either at no cost or for a nominal fee. These centers use primitive grinding and amalgamation to extract less than 30% of the gold to give back to the miners. They retain the tailings to be processed by cyanidation, where they extract 50 to 80% of the residual gold using rudimentary leaching processes. They also sell mercury to the miners, and the cyanidation of the Hg-rich tailings produces highly toxic Hg(CN)₂, which is usually dumped into the local drainages [67,68,69,70]. These centers are responsible for a significant portion of sales and the use of mercury. In a heuristic way,

Table 1. Empirical estimate of the main Hg polluters in AGM.

	Micro-Miners	Processing Centers
Number of AGMs in the world	90%	10%
Gold production	20%	80%
Loss of Hg	10%	90%
Attention to the intervention projects	100%	0%

shows that they might be responsible for 90% of the Hg pollution from AGM as they carelessly process thousands of tonnes of ores per month, always using mercury and cyanide. We believe that no project has effectively addressed these centers, as they wield considerable political influence in developing countries and are resistant to changing their exploitative business model. Most mercury elimination initiatives focus on micro-miners, processing around or less than 2 tonnes of ore/day, who are more numerous but likely contribute only around 10% of mercury emissions and releases, given their limited daily ore processing capacity. Reducing mercury use is a considerable problem; without local governments’ help, the centers will proliferate, exacerbating mercury pollution.

The number of artisanal miners tends to increase when the price of gold is higher than USD 3100 per troy ounce, or USD 100 per gram (April 2025). With no permanent training, no commitment from governments, and no enforcement, many individuals will keep risking their lives in unsafe mines and unhealthy Processing Centers. Despite the complexity of the AGM sector, governments from developing countries are usually unprepared to deal with the mercury problem. Given the scarcity of technical personnel capable of comprehensively understanding the social, environmental, economic, and technological dimensions without political interests, intervention projects would likely always be unsustainable, and the problem will persist for future generations.

6. A New Generation of Researchers and Engineers

Despite the less-than-optimal outcomes of past interventions aimed at reducing mercury use over the past decades, an increasing number of researchers and engineers now acknowledge the necessity of integrating technical, social, and cultural factors before proposing any alternatives to mercury use in AGM. This new approach combines field-based assessments of ore mineralogy, gold recovery efficiencies, and the socioeconomic context of mining rather than imposing standardized solutions. Building trust through participatory methods, in which miners collaborate to design, test, and optimize technologies that align with their priorities, addresses the practical challenges of ore variability, financial, and skill-based constraints of local miners and the preservation of cultural practices, thereby reducing the risk that a new process will be abandoned once external project support ends.

Field and technical professionals must continually stress the importance of detailed diagnostic studies to clarify gold liberation characteristics and identify optimal processing strategies. Systematic sampling and balance measurements of gold losses in existing circuits pinpoint the reasons for low gold recoveries [42]. Once this baseline is established, technical improvements such as modern milling and mercury-free gold recovery techniques can be implemented, accompanied by culturally sensitive training programs, to enable miners to recover a higher percentage of gold, laying the groundwork to reduce or eliminate mercury use.

A central objective for a new generation should be to demonstrate that better technologies and practices yield tangible economic benefits. These include enhancing gold recovery rates, eliminating mercury usage as well as converting mining waste into valuable materials for construction or other industrial applications [71]. By coupling measurable improvements in gold recovery with clear health and environmental gains, miners become stakeholders in solutions that arise within their communities rather than passive recipients of external directives. Case-specific, collaborative approaches can gradually redefine how mercury reduction projects are designed and implemented, forging a path toward more sustainable and culturally integrated AGM operations.