In 1956, in the quiet seaside town of Minamata on the southwestern coast of Japan’s Kyushu Island, cats began to behave very strangely. They convulsed, displayed excessive salivation, and gradually lost the ability to walk. Then, dead birds began to fall out of the sky. Shellfish opened and decomposed. Fish also displayed abnormal behaviors, eventually floating up to the surface of the Shiranui Sea. Many of the ailing cats wandered into the sea and drowned. Soon, there were no more cats alive in the area.
As if on cue, humans then began to fall sick, reporting severe numbness of the limbs and the inability to speak or eat. It wasn’t until 1959 that it was fully acknowledged that a disease was responsible for these phenomena. The deaths in the cats, birds, fish and humans were all connected. In humans we call it Minamata disease (MD), a debilitating and chronic condition caused by consuming fish poisoned by methylmercury (MeHg).
To date, MD has claimed over 1,000 lives, while several thousand others have chronic symptoms. Children have been born with congenital forms of MD, and it could contribute to abnormally high rates of cerebral palsy.
Although an acetaldehyde plant run by the Chisso Corporation (then called Shen Nichitsu) was identified in 1959 as the source of the MeHg, it was not until 1968 that the plant was closed. In 1973, Chisso was officially found guilty of negligence. By that time, the contamination had spread across Minamata Bay, and it took 10 years and over $487 million (48.5 billion yen) to dredge its 1.5 million cubic meters of sludge. Nets preventing contaminated marine life from leaving the bay were in place from 1974 to 1997. Today the bay is considered safe to fish in again.
On October 10, 2013, 57 years after that first outbreak and 16 years after Minamata Bay was declared contamination-free, 92 countries signed the Minamata Convention, agreeing to use mercury-free products and curtail mercury-emissions.
“Mercury is a chemical of global concern owing to its long-range atmospheric transport, its persistence in the environment once anthropogenically introduced, its ability to bioaccumulate in ecosystems and its significant negative effects on human health and the environment,” states the Minamata Convention.
Also called quicksilver, it is liquid at room temperature and evaporates easily. It can neither be created, nor destroyed. Once released into the atmosphere, it retains the dubious distinction of being able to travel thousands of kilometers, alternating between air, soil and living organisms. It becomes concentrated as it travels up a food chain, eventually accumulating in detrimental levels in top predators and the people who eat them. While mercury contamination of the hydrosphere (the global water system) may be contained via similar measures as those used for Minamata Bay, air pollution is currently virtually impossible to control.
According to the United Nation’s Environment Program (UNEP), “once deposited in soils and sediments, mercury changes its chemical form, largely through metabolism by bacteria or other microbes, and becomes methylmercury, the most dangerous form for human health and the environment.”
Although mercury absorption from the air is dangerous, its bioaccumulation in marine life is far more threatening because it can lead to a large amount of mercury consumed in a single meal.
Mercury is readily encountered in an urban environment, even in places with no connection to chemical industries. It is used in a range of products, from electronic devices, fluorescent lamps and batteries, to cosmetics such as mascara and skin lightening creams.
The UNEP, in its Global Mercury Assessment of 2013, reports that most of the 600,000 tons of mercury deposits in the world today are found in a handful of countries – China, Kyrgyzstan, Mexico, Russia, Slovenia, Spain, Ukraine and Peru. It is encouraging to note that the UNEP also reports that the demand for mercury has dropped considerably in the last 50 years – sinking from 9,000 tons a year in the 1960s to roughly 4,000 tons in 2006 – with this trend likely to continue in the future. Unfortunately, there are two major exceptions to this rule that together account for nearly half the global demand for mercury. The first is the production of vinyl chloride monomer, used to make polyvinyl chloride (or PVC), and the second is artisanal and small-scale gold mining (ASGM).
The Minamata Convention defines ASGM as “gold mining conducted by individual miners or small enterprises with limited capital investment and production.” The UNEP suspects that 10-15 million people, including three million women and children, are involved in non-industrial scale gold mining activities across 70 countries. Artisanal gold mining contributes 15 percent of the world’s gold production, but uses 90 percent of its workforce. In 2011 alone, nearly 1,400 tons of mercury was used to mine gold, which accounts for 24 percent of the global consumption of mercury. Most of that mercury is not recycled, leaving artisanal gold mining the largest source of mercury pollution to the environment.
When mercury and gold are brought into contact with each other, even if the gold is still in a sediment or crushed ore, they form a mixture or an “amalgam” of equal parts of each metal. This is particularly useful when gold exists as fine particles in river sediment, and is thus invisible to the naked eye. To retrieve the gold from the amalgam, the mixture is subjected to high temperatures to evaporate the mercury, leaving only the gold behind. Thus, mercury pollution can occur at several points in this process: inappropriate storage and handling, overenthusiastic usage and during the final evaporation step.
Mercury is a powerful neurotoxin, and it can cause a variety of chronic symptoms and congenital deformations particularly in developing fetuses and young children. In its vapor form, it is rapidly absorbed into the blood stream after being inhaled, where it damages internal organs, the central nervous system and the immune system. Neurological symptoms in adults include tremors, memory loss and cognitive dysfunction. In children, however, the symptoms are magnified and include mental retardation, seizures, delayed development, language disorders and memory loss. It has even been shown that children with higher levels of mercury in their bloodstream are more likely to be diagnosed with attention deficit disorder.
Due to the significant health risks and the continually increasing financial cost of mercury, other methods to mine gold have been proposed. Panning, which uses gravity to separate gold from ore or sediment, can eliminate the use of mercury completely. Mercury-use efficiency can also be increased by concentrating ore before amalgamation, where the released mercury can be captured and recycled with fume hoods or retorts to minimize its impact on the environment.
A video by the US EPA that proposes a novel mercury capture system.
So why use mercury at all, particularly when alternatives exist? A variety of social and practical factors contribute to the appeal this chemical element has for small-scale mining operations. Its use is quick and easy, where alternatives involve longer processing times. A single person can independently mine gold with mercury, and it can be used in most field conditions. It does not necessitate large infrastructural investments, and often, its use is not a choice for a worker who is simply following orders. In some cases, miners are unaware of the risks, and those who are aware often cannot afford the alternatives.
A Spotlight on Peru
The Madre de Dios Department (MDD) of Peru is home to Manu National Park, listed by UNESCO as a World Heritage Site for its “biological diversity that exceeds any other place on earth.” The National Park is only one of the many forested areas within the Department, which also contains the Tambopata National Reserve, the Los Amigos Conservation Concession and the Purús Communal Reserve.
Small-scale gold mining abounds on the banks of the Madre de Dios River, which bisects the Department from west to east. There have been several strikes and protests in recent years, some violent, in response to government regulation of mining permits in the region. A lethargic and inefficient bureaucracy and minimal supervision has resulted in a booming mining economy that is primarily illegal. In the last five years, the Peruvian government has aggressively combated small-scale illegal mining along the banks of the Madre de Dios River. Unlike in 2008, when large mining barges could be seen on the river, today’s small-scale mining has been forced to be subversive – mining families have moved their establishments deeper into the jungle, leaving minimal traces of their presence along the river’s edge.
Watch the four-minute trailer to Amazon Gold, a documentary narrated by Academy Award winners Sissy Spacek and Herbie Hancock. It reveals a “disturbing account of a clandestine journey that bears witness to the apocalyptic destruction of the rainforest in the pursuit of illegally mined gold.”
A recent study by a team from Stanford University led by Greg Asner used airborne mapping and high-resolution satellite imaging to monitor the extent of deforestation in the Madre de Dios. They discovered that large swathes of forest have been torn down at unprecedented rates, and that the geographic extent of mining in the area has increased 400 percent from 1999 to 2012. Aerial imaging depicts the Madre de Dios River as a dark chocolate brown, full of disturbed sediment and contaminated water being carried for miles downstream. Given that nearly 200 tons of mercury is deposited annually in the Arctic from the rest of the planet via air currents and aquatic systems, it is highly probable that the Amazon river has received mercury released from mining along its tributary, the Madre de Dios River.
Güido Lombardi voiceover detailing the damage caused by gold mining in Madre de Dios in southeastern Peru (Spanish)
Studies also indicate that superstitions surround the use of mercury in the Madre de Dios, and may be affecting miners’ rates of exposure. Katy Ashe of Stanford University reported in 2012 that some miners believe that they must stand close to the gold to prevent its loss, which may increase mercury inhalation during the evaporation phase of mining. Ashe also found that many miners believe that mercury is not harmful unless it comes into contact with a wound, and is useful as a laxative. She documented that levels of fish consumption were the strongest predictors of levels of mercury in the residents of the Madre de Dios, with the predominantly male mining population having far higher levels than women in the area.
In 2013, Stanford University’s Carnegie Amazon Mercury Ecosystem Project revealed that 60 percent of the fish species sold in Puerto Maldonado, the capital of the MDD, contained mercury at levels higher than those specified by international limits. A whopping 78 percent of adults in Puerto Maldonado had mercury concentrations above international reference limits, of which women of childbearing age (16 – 49 years) had the highest average mercury levels of any other group.
The Future of Artisanal Gold Mining
According to a study by Kevin H. Telmer and Marcello M. Veiga, as reported in a volume titled Mercury Fate and Transport in the Global Atmosphere, an estimated 640 to 1,350 metric tons of mercury (average 1000 metric tons) is released by ASGM alone each year. Thirty-five percent of these emissions go directly into the atmosphere, and the rest is released into the hydrosphere.
They report that as of January 2008, the ratio of mercury to gold prices was 1:1,650. Despite a reduction to roughly 1:567 today, these numbers still imply that mining with mercury is economically appealing. In short, Telmer and Veiga state that mercury is “cheap, simple, fast, independent, and reliable.”
The signatories of the Minamata Convention have been charged with a challenging task. Despite mercury’s appeal, these nations have agreed to take steps toward eliminating the use of mercury and mercury compounds in mining activities within their borders. They plan to use education, outreach and capacity-building initiatives, while providing technical and financial assistance to miners transitioning to alternative mining strategies.
To put this into perspective, Telmer and Veiga predict that if the top ten countries (sans China) using mercury in ASGM were to adopt emissions control methods such as fume hoods and retorts, and clean mercury before use to make it more efficient at binding to gold, mercury emissions would drop from 400 metric tons to approximately 240 metric tons per year. The Minamata Convention can thus contribute significantly towards reducing the global load of mercury emissions.
However, there is another layer of complexity to this economic system. Deforestation, which can cause extensive erosion, can also release mercury into rivers that had previously been trapped in soils. In 2010, this amounted to nearly 260 tons of extra mercury re-entering water systems.
In 2011, Jennifer Swenson and colleagues from Duke University examined gold prices and deforestation rates in the Madre de Dios Department. Their findings demonstrated that the price of gold is tightly linked with increases in Peruvian imports of mercury over time, which in turns spurs deforestation in one of the most biodiverse places on earth.
“We find that since 2003, recent mining deforestation in Madre de Dios, Peru is increasing nonlinearly alongside a constant annual rate of increase in international gold price (18 percent/yr),” write the authors in the journal PLoS ONE.
Although the convention could be successful in curbing mercury emissions in the future, it makes no mention of deforestation as a potential contributor to the movement of mercury into water systems. Nevertheless, it is a strong step forward and one that has been a long time coming for children and families across the planet.
“Many of the actions to reduce mercury emissions and releases into the environment also have multiple, green economy benefits that can assist other international aims,” said Achim Steiner, UNEP Executive Director, in his address to signatories from nearly a hundred countries waiting to sign the Minamata Convention. “In other words this treaty can contribute to wider sustainability aims including a new and universal climate agreement by 2015 to come into effect by 2020.”
- Ashe, K. (2012). Elevated mercury concentrations in humans of Madre de Dios, Peru. PloS one, 7(3), e33305.
- Asner, G. P., Llactayo, W., Tupayachi, R., & Luna, E. R. (2013). Elevated rates of gold mining in the Amazon revealed through high-resolution monitoring. Proceedings of the National Academy of Sciences, 201318271.
- Harada, M. (1995). Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. CRC Critical Reviews in Toxicology, 25(1), 1-24.
- Swenson, J. J., Carter, C. E., Domec, J. C., & Delgado, C. I. (2011). Gold mining in the Peruvian Amazon: global prices, deforestation, and mercury imports. PloS one, 6(4), e18875.
- Telmer, K. H., & Veiga, M. M. (2009). World emissions of mercury from artisanal and small scale gold mining. In Mercury fate and transport in the global atmosphere (pp. 131-172). Springer US.
- UNEP, 2012. A Practical Guide: Reducing mercury use in artisanal and small-scale gold mining.
- UNEP, 2013. Global Mercury Assessment 2013: Sources, Emissions, Releases and Environmental Transport. UNEP Chemicals Branch, Geneva, Switzerland.
- UNEP, 2013, Mercury: Acting Now! UNEP Chemicals Branch, Geneva, Switzerland.
- UNEP, 2013. Mercury: Time to Act. UNEP Chemicals Branch, Geneva, Switzerland.
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