In the world Ghana is among the top 10 gold producers. One third of Ghana’s gold is mined in artisanal and small-scale mines, which usually operates illegally and locally known as galamsey (gather and sell) and employs children from poor background.
Across Africa, from Mali to Tanzania to Zimbabwe, millions of people, including children, work in small gold mines. Artisanal and small-scale gold mining is a vital source of income, but it is also very dangerous because miners use toxic mercury to separate the gold from the ore.
These people in mining areas are exposed to mercury from the moment of their birth.
How mercury contaminates the environment
In mining operation, mercury is used to recover tiny pieces of gold that is mixed in soil and sediments. Mercury and gold settle and combine to form a mixture called amalgam.
Gold is then extracted by evaporating the mercury. About 15 million of small artisanal miners around the world risk their lives every day, not just because they work in dangerous conditions, but also because they are constantly exposed to toxic chemicals.
While there are cleaner and safer alternative practices and technologies, artisanal miners often ignore the hazards that mercury poses to human health and lack the capacity, funds, and incentives to adopt good mining practices.
When gold miners use mercury to amalgamate gold, they should be aware that they can easily contaminate themselves, their families, and their neighbours, as well as people living considerable distance away from their worksites.
The way the contamination occurs depends on how the miners do their work. For example, if the whole ore is amalgamated and discharged without adequate settling ponds, or if mercury contaminated materials are dumped directly from a raft into a river, mercury will be discharged downstream and dispersed over a very wide area where it can transform into methylmercury in the sediments at the bottom of the rivers, lakes or streams.
Methylmercury is easily absorbed by worms, snails and insects and becomes highly concentrated in fish, especially the piscivorous species (fish that eat other fish). Eating fish contaminated by mercury from mining activities can pose a great health risk to people living downstream of mining areas.
Likewise, mercury vapour emitted from open pan amalgam burning is dispersed in the air. Most of the vapour settles onto the ground and can contaminate soils up to two kilometres downwind from burning. Some vapour however travels long distances and comes down with rain. If the miners amalgamate concentrates in pools, mercury tends to be concentrated within a relatively small area, forming a local hotspot, i.e. a site with high concentration of mercury-contaminated material.
Environmental mercury contamination can be caused by present-day mining, or by historic and abandoned mining sites that continue to emit mercury to the air or water for many years after mining operation has stopped. It is difficult to obtain reliable, quantitative data about how much mercury is released from active artisanal gold mining sites because miners do not freely provide information about the amount of mercury they use.
At abandoned sites, determining the extent and magnitude of mercury contamination is even more difficult. Analyses of water, sediments and soils surrounding mining sites can provide only estimates of the amount of mercury released.
To obtain reliable figures about the amount gold produced or the amount of mercury lost, it is necessary to build a trust relationship with miners to guarantee access to their mining and processing sites. Gaining trust takes time, but without it, it is very difficult to understand how much mercury is used and lost at each unit of operation.
Ultimately, remediation of mercury contaminated sites may be necessary to prevent further exposure of human populations, and to ensure that mercury does not continue to be released into the environment and eventually become methylated.
We must protect our environment: Fate and Partition of mercury in the environment
Mercury released during amalgamation in ponds or next to rivers, and especially during burning of amalgam, contaminates the soil and water of the local environment. This mercury continues to evaporate from soils around amalgamation areas and will continue to contaminate the air that is breathed by miners and their families.
Mercury lost during amalgamation and during burning can be washed into ponds and streams. Mercury deposited in water can be transformed into methylmercury which builds up in fish. While the fish themselves are not affected, frequent consumers of fish downstream from artisanal gold mining areas can become mercury intoxicated–it is irresponsible to contaminate an environment and subject non-miners and innocent people to mercury contamination.
When amalgam is burned, mercury vapour is carried by the air to very distant places. Likewise, when mercury is used with copper plates (and other forms of whole ore amalgamation) the sand and silt flowing over the plates scours mercury from the plate and carries it in the river to regions far from the mines.
Microscopic droplets of mercury become attached to fine, muddy sediment particles which travel easily downstream, far away from mining areas. Even if amalgamation is conducted in enclosed ponds, elemental mercury adhered to small sediment particles can be washed into regional stream systems during rainy periods.
In a slow-moving area of the stream, the particles sink and find reducing conditions (rich in organic matter) at the bottom of the river. Then, through a biological process, bacteria can produce methylmercury. The methylmercury formed does not stay in the water and it is quickly taken by organisms and it goes up into the food chain to become concentrated in fish, especially the carnivorous species. The more sediment particles introduced to the water, the more that mercury is transported to other places downstream. (Note that metallic mercury is not soluble and does not stay in the water.
There is no health risk from drinking clear or filtered water from streams. However, because mercury can be attached to the fine sediment particles, it is not advisable to drink dirty water.) People must not eat fish that have been grown in amalgamation ponds or near streams that might receive mercury contaminated water.
Amalgamation should only occur in ponds that are dedicated for this purpose; similarly, fish should only be grown in special dedicated ponds. Water that has been contaminated with mercury or that has been used for amalgamation must not be used for cooking, bathing, or drinking.
It is important that forests around mining areas are protected and are not cut down. These “buffer zones” allow the sediments to settle locally, preventing the transport of mercury attached to fine muddy particles from reaching streams or lakes where it can be transformed into harmful methylmercury.
Similarly, it is also critical that residual mercury contained in amalgamation ponds does not reach open aquatic systems; efforts should be made to site amalgamation ponds in safe places, protected from flooding during rainy seasons. Mercury-contaminated tailings should be disposed in cement-lined ponds.
Miners should be aware that mercury amalgamation can contaminate miners themselves, their families, their communities, and people living a long distance away and the environment
Health Implications of Mercury Exposure
For miners, mercury can be absorbed directly through the skin during the amalgamation process. However, the main route of exposure in small scale and artisanal miners is through inhalation of mercury vapours during burning of mercury – gold amalgams.
The absorption of mercury vapour is very dangerous and can lead to serious health problems. Most people in the world however aren’t directly affected by mining, so fish consumption is the major route of exposure for them to mercury (as methylmercury). Both mercury vapour and methylmercury affect the brain, nerves, senses (e.g., vision, hearing) and organs (liver, kidney, glands).
Elemental mercury vapour has no colour and no odour. Mercury sticks to clothing worn during burning and will continue to be a source of mercury vapor long after burning has ceased. When breathed, mercury is absorbed by the lungs and is passed directly into the bloodstream where it is carried to all organs of the body.
The body retains 80% of all inhaled mercury vapour. Wearing a dust mask does not afford any protection from mercury vapour. Mercury has no biological purpose and the human body recognises mercury as harmful. The liver and kidney attempt to rid the body of mercury that is either inhaled or absorbed through the skin.
The liver attempts to detoxify and get rid of the mercury via the digestive system. The kidneys attempt to get rid of mercury in the urine.
However, mercury can build up in the body, especially the kidneys, and can cause serious damage. Mercury levels in urine are the best indicators of recent inorganic (metallic) mercury exposure, especially from burning of mercury. Measuring mercury concentration in the breath is another useful means of determining recent exposure.
A person who has recently burned mercury or has been burning for some time will have strongly elevated mercury concentration in their exhaled breath, as the body tries to rid itself of the mercury in the bloodstream. Elevated mercury in blood or hair is regarded as a good indicator the mercury exposure has been from eating fish containing methylmercury.
To assist artisanal gold miners eliminate the use of mercury in gold mining and reduce harmful risk to their health, immediate families and the environment the government of Ghana can support artisanal miners and small scale enterprises by creating policies and market incentives and connecting them to international markets and supply chains that favour gold which uses less or no mercury in its extraction.
Massive reformation of the whole mining sector with more enforcement powers to EPA Ghana to regulate the industry and prosecute the illegal miners with hefty fines and imprisonment.
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