Source: Reuters.com                                   Date: 28 July, 2010

Colombia's gold bonanza has a dark side, U.N. experts have said. Mercury poisoning has been spreading from miners to the population of a region where they use mercury to extract the precious metal. Colombia is one of the world's top mercury polluters, as 50 to 100 metric tons of mercury are lost annually in the process of capturing gold while soaring prices push miners and artisans to extract ever more of the yellow metal.

"As prices of gold have been increasing, more artisanal miners are mining and processing gold using mercury which is accessible, easier and cheaper to use," said an adviser to the UN Global Mercury Project. Colombia is the world's No. 1 mercury polluter per capita from artisanal (small-scale) mining, he said. "The number of artisanal miners in the country is also increasing."

Miners have used mercury to separate gold for decades, but part of it is lost in the process, contaminating rivers and soils. The environment ministry currently allows mercury but may soon forbid it, with a few exceptions. In some places, they use the most damaging process, adding around 120 grams of mercury to 60 kilograms of ore, without condensing or capturing the mercury. As a result, mercury levels in some urban areas can be 1,000 times higher than the levels accepted by the World Health Organization.

About 15,000 to 30,000 artisanal miners producing between 10 and 20 metric tons of gold per year in four municipal areas alone release 50 metric tons of mercury annually. The number of kidney transplants has been going up because mercury vapor stays in the kidneys. Among miners, mercury exposure can be linked to memory loss, language issues and chronic headaches.

The United Nations calls for a gradual elimination of mercury in mining as miners switch over to use of centrifuges, which allow for greater gold extraction than mercury.