Perhaps the most insidious aspect of this, both for people and the environment, is the use of mercury to recover minute gold fragments dispersed in soil and rocky sediments. A heavy metal found in the natural environment, mercury can become highly toxic when used in its elemental – or liquid – form. Liquid mercury evaporates even at relatively low ambient temperature, and can be dispersed over long distances by the wind. It binds with gold to form an amalgam, which is then heated to a high temperature to vaporise the mercury and extract the precious metal. This is often done with rudimentary equipment such as a blowtorch or – in the worst circumstances – over stoves in the miners' own homes. Sometimes cyanide is used on the mining tailings to extract yet more gold, and it combines with the mercury to make compounds that are easily dispersed in water and taken up in food chains.
Breathing in mercury can damage the nervous, digestive, and immune systems. Ingesting it can cause the condition called Minamata Disease, after a coastal city in Japan where humans and animals ate mercury-laden fish and shellfish from the local bay. Its most notable symptoms are convulsions, loss of muscle coordination, and damage to vision, speech, and hearing. Pregnant women exposed to the toxic metal are susceptible to giving birth to babies with congenital diseases.
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