Reducing Mercury Exposure among the Artisanal Gold Miners using a modern gold processing technology: A Case study of Amudat District in Uganda

Executive summary

Currently there is no policy on the application of Mercury (Hg) in Artisanal Gold Mining (ASGM) and processing industries in Uganda. Hg is a toxic metal that can cause a variety of adverse health effects when exposed to the body. Artisanal gold miners (AGM) use Hg to extract gold from Ore. On 28 Nov 2017, Ministry of Health received notification through Daily Monitor newspaper of over 100 suspected Skin infections among AGM in Amudat District. The miners were reported to be engaged in massive use of mercury in purifying gold. We conducted an epidemiological investigation to quantify mercury exposure among residents of an AGM in Amudat District, determine risk factors for mercury exposure and recommend evidence based control measures. Symptoms included fever (52%), headache (33%), muscle ache (33%), cough (29%), malaria (28%) as well as skin rashes, peeling skin on hand and numbness among 5% of the respondents (figure1. All the participants inter- viewed appeared to be healthy during the time of this survey. 63% of the miners had ever used mercury during gold processing. 50% had stood in a dam of water mixed with mercury, while 42% had mixed mercury with gold and water. Dumping of Wastes (water, sand, gold and mercury) in the nearby river was also observed. Our findings suggest that mercury exposure may be widespread in AGM industries in Uganda. All residents, including children and adults had exposure to mercury during the various stages of gold processing. Thus, our findings recommended the need for a policy to reduce the use of mercury exposure in artisanal gold mining communities.

Background

Currently there is no policy on the application of Mercury in Artisanal Gold Mining (ASGM) industries in Uganda and yet Mercury is a toxic metal that can cause a variety of adverse health effects when exposed to the body depending on the form of mercury, the pathway, quantity, and duration of exposure [2]. Mercury (Hg) is a naturally occurring element found in air, water, and soil. It is distributed through- out the environment by both natural and human processes.

Mercury is found in various Inorganic (elemental) and organic forms (Methyl mercury). Once in the environment, elemental mercury can be transformed by bacteria into methyl mercury. Methyl mercury then bio accumulates in fish, shellfish and plants which can be consumed by Humans [1]. Artisanal Gold Miners use mercury to extract gold from ore by forming ―amalgam‖—a mixture composed of approximately equal parts of Mercury and gold[3]. To remove the mercury, its typically heated in an amalgam furnace. The mercury evaporates into the environment, while the gold stays behind. When it enters the water, it can transform into organic mercury com- pounds, such as methyl mercury, and bio accumulate in fish. This process presents three major potential routes of mercury exposure(1) miners can have dermal exposure when they mix elemental mercury with gold ore; (2) elemental and inorganic mercury vapors can be inhaled when amalgams are heated; and (3) methyl mercury can be consumed from contaminated fish [3]. In developing countries, the ASGM industry, which produces approximately 300–400 tons of gold annually, has rapidly expanded over the last two decades and is estimated that more than 15 million people depend directly, and 100 million people depend indirectly, on the gold mining sec- tor[4]. The ASGM sector is responsible for 37% of all anthropogenic mercury emissions to the environment [4]. The aim of our policy brief is to recommend control interventions to both the Ministry of Health and Ministry of Water and Environment of Uganda to control the wide use of Mercury in ASGM industries in Uganda.

Approaching and results

On 28 Nov 2017, Ministry of Health received notification through Daily Monitor newspaper of over 100 suspected Skin infections among ASGM in Kabisha and Chepkarat parishes, Amudat District. Eight goats were also reported dead after drinking water contaminated with mercury a fortnight ago. The case-patients presented with skin pain, itching, and dark skin. The miners were reported to be engaged in massive use of mercury in purifying gold. We set out to conduct an epidemiological investigation to quantify mercury exposure among residents of an artisanal gold mine in Amudat District, determine risk factors for mercury exposure and recommend control measures.

Mining Processes

The gold mining process starts with survey and identification of potential sites by the locals. This is followed by manual digging of holes which is later supported by a generator to power further drilling until the hole reaches stone linings (gold ore) which contains gold. At Cheptekol mine, the processing of gold involves crushing the ore using stone milling machine which turn the ore into powder. This process normally generates a lot of dust and exposes miners who don’t have protective gears. After crushing, the powder is then taken into a dam of about 3m³ approx 2000 litres of water and washed in the basin using mercury and water by women using bare hands. About 200 grams of mercury is applied at this stage to amalgamate the small particles of gold. Hg is then squeezed from the gold into the main dam and re used for about four times. The gold amalgam is then burnt using gas to remove the remaining mercury. This is normally done by the specialist employed by the association. The gold is then ready for sale

Descriptive findings of the investigation:

65 gold miners were interviewed about their expo- sure to mercury and possible infections related to mercury exposure. 36 (55%) of the gold miners were females and 29 males (44%). The median age was 28 years (Range 12-60). 21 (32%) of respondents had ever fallen sick from 1^st August 2017 till the time of interviews. Symptoms included fever (52%), headache (33%), muscle ache (33%), cough (29%), malaria (28%) as well as skin rashes, peeling skin on hand and numbness among 5% of the respondents. Majority of the gold miners (63%) had ever used mercury during gold processing. 51% had stood in a dam of water mixed with mercury, while 42% had mixed mercury with gold and water.

Conclusions

Mercury exposure may be widespread in ASGM industries in Uganda. All residents, including children and adults had exposure to mercury during the various stages of gold processing. Once absorbed, Mercury is transported to the circulatory system, where it attacks red blood cells, the kidneys, and the central nervous system.

Implications

The inhalation of mercury vapour can produce harmful effects on the nervous, digestive and immune systems, lungs and kidneys, and may be fatal. The inorganic salts of mercury are corrosive to the skin, eyes and gastrointestinal tract, and may in- duce kidney toxicity if ingested. Neurological and behavioural disorders may be observed after inhalation, ingestion or dermal exposure of different mercury compounds(5).

Recommendations

1. Warning community members about adverse health effects from mercury exposure.
2. Creating centralized amalgamation centers located away from commercial and residential areas with amalgam furnace retorts to decrease emissions of mercury
3. Introducing modern gold processing technology which does not utilize mercury.
4. There is also urgent need to measure the long term health outcomes of mercury exposure among the gold miners through conducting a follow up study.