Mercury exists in three forms: elemental mercury, inorganic mercury compounds, and organic mercury compounds. All forms of mercury are extremely toxic, and each form makes different kinds of health effects to human beings and ecosystem, even though mercury have been long used for scientific research applications, gold extraction process, and in amalgam for dental restoration in some parts of the world.
Exposure to mercury threatens to human health especially developing fetuses and young children are at the higher risk.
The inhalation of mercury vapor can produce severe effects on the central nervous system, digestive and immune systems, lungs and kidneys, and may be fatal.
Mercury occurs naturally in the earth’s crust, but human activities, such as burning of coal, oil and wood, mining and fuel combustion, have led to widespread global mercury pollution. Mercury release occurs by both naturally such as volcanic eruption and land emission through soil, and anthropogenic processes (human activities) such as artisanal and small – scale gold mining, fossil fuel burning and primary production of non-ferrous metals. Although it is relatively small percentages of emission, the other sources of mercury emission are cement production, consumer products waste, contaminated sites and chlor-alkali industry.
In the regions closer to plate tectonic boundaries, where soils are enriched with minerals such as cinnabar containing Mercury sulfide (HgS) released by either natural weathering of the rocks or by geothermal reactions.
Mercury is precipitated into the oceans predominantly from air in three main forms; in the state of gas (Hg0) by the process of air-water exchange, wet and dry precipitation of inorganic mercury (Hg2+ or HgII) and particle-bound mercury (Hg(P)). The other natural water channels also deliver mercury into the ocean. Organic mercury compounds called methyl mercury can also be discharged from these which will undergo chemical transformations such as oxidation-reduction, adsorption processes and methylation-demethylation.
Global Mercury Assessment 2018
Global Mercury Assessment 2018 was conducted by an international team of experts convened through a collaboration between UN Environment and the Arctic Monitoring and Assessment Programme (AMAP).
Global ASGM Statistics
The largest source of mercury emissions of anthropogenic activity ever made on earth is artisanal and small-scale gold mining known as ASGM where mercury is used in the traditional method of amalgamation to extract gold from the ore rock. ASGM activities are also sources of social problems, such as land tenure issues, social instability such as migration, and conflict between residents.