Mercury and the environment
Mercury is a known neurotoxin, and elevated blood mercury levels may lead to retardation and deformities in children
Africa hosts a third of the world’s mineral wealth and has significant deposits of gold, Zimbabwe is no exception.
The country’s endowment with vast gold reserves has given rise to artisanal gold mining, whose use of mercury in gold processing has brought several environmental and health impacts.
World over, emerging evidence indicates that artisanal and small scale gold mining related mercury contamination, is contributing to serious health and ecological impacts and has raised concern among environmentalists.
Mercury is a persistent, highly toxic heavy metal whose continued inhalation can cause death. It is estimated that artisanal small scale miners, mostly from vulnerable backgrounds, active in the gold and diamond sectors, constitute more than half of all mineral exploitation in the world.
UN environment estimates that 3,5 million people are at risk of health impacts in artisanal and small scale gold mining sector of which 2,5 million are in Africa. A research (Global Mercury Project) by the United Nations Industrial Development Organisation (UNIDO) which was conducted between 2007 to 2012 revealed that Zimbabwe had an estimated 500 000 artisanal gold miners, the number is expected to have increased over the years.
The Minamata Convention on Mercury
Concerns on the negative impacts of mercury gave rise to the promulgation of the Minamata Convention on Mercury of October 2013. The Convention is an international treaty designed to protect human health and the environment from human induced emissions and releases of mercury and its compounds.
The Convention was a result of international action aimed at managing mercury in an efficient, effective and coherent manner, while member states work towards its total elimination.
Zimbabwe is one of the 128 countries which signed the convention and is working towards ratification.
The document puts an obligation on member states to ensure there is informed consent from the receiving state in relation to the trade in mercury or mercury based products. Trade in mercury or mercury based products will be restricted to allowed purposes under the instrument and also domestic law, and only in quantities needed for those purposes.
The instrument will also put restrictive measures on the use of mercury especially in the mining sector. There is a need for the development of sustainable technologies to extract gold in preparation for the restrictions that will be imposed on trade in mercury.
Once ratified, the main benefit, of the document is that it will be a reference point or provide direction on how national legislation can be developed to tackle the ongoing problem of controlling the use and influx of mercury into the country and prevent the possibility of Zimbabwe being a dumping ground of such hazardous substances.
Large-scale public health crises due to mercury poisoning, such as Minamata disease and Niigata Minamata disease, drew attention to the issue.
In 1972, delegates to the Stockholm Conference on the Human Environment witnessed Japanese Junior High School student Shinobu Sakamoto, disabled as the result of methylmercury poisoning.
Why is mercury bad for the environment?
Toxic mercury vapour from the process of burning the amalgamimpacts negatively on miners, their families and nearby communities. Most gold mining activities are carried out in rivers and streams which drain into dams and lakes.
Mercury contaminates water, accumulates in sediments and bio-accumulates in fish and tissues and other aquatic species. Its effects on the environment include the following:
Mercury in the air may settle into water bodies and affect water quality;
Methylmercury accumulates in fish at levels that may harm fish and the other animals that eat them;
Methylmercury exposure on wildlife can cause mortality (death), reduced fertility, slower growth and development and abnormal behaviour that affects survival;
Research indicates that the endocrine system of fish, which plays an important role in fish development and reproduction, may be altered by the levels of methylmercury found in the environment;
Once present in aquatic ecosystems, elemental and inorganic mercury can undergo chemical transformations to methylated mercury species and enter the food web and high level predators such as birds, sea mammals and humans could be in danger of contamination.
The Environmental Management Agency is conducting an intensive awareness programme on artisanal miners and other stakeholders, in all the 10 provinces, on the dangers associated with the use of mercury, from the 9th to the 20th of July 2018.
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