Artisanal and small-scale mining is defined as mining by individuals, groups or cooperatives with minimal or no mechanization often in the informal sector of the market.
It is an important economic activity in many developing countries across Africa, Asia and South America. The process accounts for a quarter of the world’s gold output.
Studies by Spiegel and Veiga, 2010, estimated that 13 million people globally depend on artisanal mining for their livelihood, majority of who are in developing countries.
Women and children comprise of approximately 30 per cent of these miners, with 40-50 per cent of these coming from Africa.
Small-scale gold mining occurs near the surface and within unconsolidated rocks, the most frequent being deposits contained in riverbed alluvium and colluviums and altered upper portions of quartz veins.
The miners employ traditional techniques and usually operate under hazardous, labour intensive, highly disorganised and illegal conditions. To free gold particles, they add mercury to the ore forming a mercury-gold amalgam, what is called the amalgamation method.
The amalgam is then cleaned with water and later roasted in high temperatures to release the gold from the mercury. This process is estimated to globally discharge to the environment up to 1,000 tonnes of mercury per annum, accounting for one third of all global anthropogenic mercury pollution.
Studies also show that an estimated 300 tonnes of mercury are volatilised directly to the atmosphere per annum, while 700 tonnes are discharged in mine tailings into soil, rivers and lakes.
Mercury is considered by the World Health Organization as one of the top 10 chemicals of major public health concern. Exposures to mercury, even in small quantities, are associated with serious health problems, including complications during fetal and early life.
According to WHO, elemental and methyl mercury are toxic to the central and peripheral nervous system, causing harmful effects on the nervous, digestive and immune system, lungs and kidneys.
The inorganic mercury released to the environment may be converted by microbial activity to organic forms of mercury, like methyl-mercury, a potent neurotoxin, which damages the central nervous system and is especially toxic to fetuses (International Finance Corporation & World Bank, 2010).
Impacts on cognitive thinking, memory, attention, language and fine motor and visual spatial skills are seen in children exposed to methyl-mercury in the womb. Consumption of mercury contaminated aquatic foods is a threat to both humans and other fish-eating animals as methyl mercury has protein binding properties, making it readily bio-accumulate and bio-magnify in aquatic food chains.
Gold mining in Kenya has been going on for close to a century and is now being carried out primarily by the artisanal miners.
There are several gold deposits present in Kenya, which include Macalder, Masara, Osiri, Nyalapa and Nyatworo and Mikei mines in Macalder division in Migori county.
Artisan gold mining is practiced in Migori as there is limited resources and training, and the availability of cheap but potentially dangerous method of extraction and processing of minerals, which can cause potential risks to both miners and the environment.
The miners, who use mercury, are constantly exposed through the amalgamation process as they hold the mercury with their bare hands. The mercury tailings end up in the rivers and soils due to poor disposal of the mercury once the miners use it, affecting the aquatic life. The rocks have sulphur minerals, which, when they react with water, produce sulphuric acid which increases the acidity in soil and water bodies, causing aquatic life to die.
The sulphuric acid also reacts with the sulphur minerals to produce lead and arsenic which are both toxic elements. Gold mining in Migori incorporates open-cut and underground operations, which enhance environment degradation due to high uncontrolled excavation in search of gold.
Precious metals are important as they are a source of livelihood to many people in county and they also increase the GDP. Minimal research has been done in the Macalder mines, which are a source of income for many artisan miners who use mercury in the amalgamation process.
Mercury is a heavy metal, which causes both environment and health effects. The mineral ore also contains sulphur, which forms sulphuric acid when it reacts with water, increasing acidity in soil and water bodies. The sulphuric acid formed further reacts with the sulphur minerals to produce arsenic and lead which are toxic elements according to the World Health Organization.
Recent increase in gold mining in Kenya has had a positive impact on unemployment through being a source of livelihood for many artisan miners. However, it has excess of environmental implications, causing significant damage to the landscapes.
The environment implications in the mining regions include pollution of water sources from mercury and cyanide, dust, cracking and collapse of mine pits.
At the local level, the uncontrolled digging and abandoning of pits has caused destruction of land beyond economic and technical reclamation. Mine pits not only make land unfavorable for agricultural activities following closure but also adversely impact livestock and wildlife resources, which in turn, affects locals, who depend on power and animal manure.
Continuous disposal of mine wastes contributes to air and water contamination, which are detrimental to human health, livestock and wildlife biodiversity and have serious effects on the welfare of the mining communities, especially groups of women and children.
Forty per cent of the mercury lost during amalgamation is released directly into the soil, streams and rivers, as inorganic mercury, which later converts into organic mercury. The remaining 60 per cent of mercury is released to the atmosphere when the gold amalgam is heated during the purification process and is often inhaled.
Heavy metals are also seen to affect the microorganisms as resistant genes are known to develop in the bacteria as a result of continued exposure of these bacteria to heavy metal pollution to the environment leads to increased antibiotic resistance.
Aquatic life is also affected as they accumulate toxins in their body through eating planktons, which absorb mercury and in the long run, the animals suffer the risk of poisoning from these heavy metals.
Pollution of water in Migori is significant. Panning is often carried out along river profiles. Evidence of river pollution includes siltation and colouration. The affected rivers are rivers Kuja, Migori and Mickey.
River Kuja is adversely affected by the Macalder tailings through a stream that passes at the foot of the tailings. During gold rushes, the large number of miners put much pressure on the environment in terms of energy resources; thus large quantities of trees are cut down either as firewood or as timber for support of weak mine workings. This causes deforestation and soil erosion.
Also, lack of sound mining techniques and procedures often result in the collapse of the wall rock and eventual subsidence of mined areas. This often results in loss of life which has always been evident in Migori County as many people have been buried by the collapse of the lands resulting from mines.
To solve many environmental problems caused by mining, there is need to check on uncontrolled excavation and abandoned mine pits that were not rehabilitated.
It is also imperative to create awareness of the dangers of using mercury with bare hands and the use of personal protective equipment during mining. The miners should also be sensitized on the dangers of mining through workshops and eco-friendly solutions should be provided to ensure green economy in the mining sector.
The government should come up with an artisanal mining policy that will have well-organized laws of operation to reduce the occupational risks. Also, comprehensible policies on mining that pay detailed attention to the mining effects of the environment and health of the miners should be structured.
Dr. John Chumo is the committee secretary, National Environmental Complaints Committee
