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Experts' Log in
Topic: Mercury Waste
Mr. Shunichi Honda is a Programme Officer at UNEP IETC joined in May 2015. His expertise is waste and chemical management including environmentally sound management of hazardous wastes and heavy me...
Number of questions: 
Posted on 04/08/2015 09:11:20
why is mercury associated with gold mining?
Does mercury cause a short term or longterm effect to the environment and people?
Thank you for your question.
In our general life, it might be difficult to imagine how mercury relates to gold mining.
However, mercury is used for various kinds of industrial processes and products because of its chemical characteristics.
One of processes using mercury is gold mining, in particular informal gold mining activities, so called “artisanal and small scale gold mining (ASGM)”.
At ASGM, ore containing gold is mixed with mercury after pretreatment, such as crushing ore into small particle.
Only gold portion in ore binds mercury: this is called as amalgamation which is an alloy of mercury with various metals. In the case of ASGM, mercury bonds with gold and forms amalgam.
The amalgam is heated to extract gold: During this heating process, mercury is evaporated and gold is remained in the process. Finally, the mercury amalgamation process extracts gold from ore.
However, mercury is released from ASGM using the mercury amalgamation process, and mercury release from ASGM includes acute (short term) and chronic (long term) adverse effect to human health and the environment.
Acute adverse effect:
When mercury is vaporized during the heating process, mercury vapour easily passes the lung of miners and other people at ASGM, mercury vapour further passes the blood-brain barrier, and it reaches the brain. In the brain, mercury vapour is oxidised and accumulated, and then accumulated mercury damages the nerve system.
Chronic adverse effect:
During the mercury amalgamation process at ASGM, mercury is released to the environment. Because mercury cannot be decomposed and it remains in the atmosphere (mercury vapour), soil (ionic mercury) and aquatic phase (methylmercury), mercury released from ASGM ends up in the food chain because of bioaccumulation and biomagnification. Eventually, mercury is eventually ingested by humans and causes adverse effect to human health.
In order to tackle the mercury issue of ASGM, UNEP has been working on various activities to reduce mercury in ASGM since mercury emission from ASGM accounts for 37% of global mercury emission. The Minamata Convention on Mercury stipulates the measures of ASGM at the article 7 to reduce, and where feasible eliminate, the use of mercury and mercury compounds in, and the emissions and releases to the environment of mercury from ASGM. Also one of the areas under the UNEP Global Mercury Partnership is ASGM.
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