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Gold Mining Boom Increasing Mercury Pollution Risk

By Andy Soos | Thu, 06 January 2011 16:34 | 0

In order to maximize gold extraction, mercury is often used to amalgamate with the metal. The gold is then produced by boiling away the mercury from the amalgam, a process which is hazardous owing to the toxicity of mercury vapor. Mercury is effective in extracting very small gold particles, but should be reclaimed in an effective and safe process.

With the price of gold at record levels. the small-scale mining sector, much of it illegal and unregulated, is expanding worldwide faster than at anytime in history and, with it, the health threats posed by mercury. This global gold rush began in Brazil in the late 1970s, before sweeping South America, Asia, and Africa, with an estimated 15 to 20 million prospectors now active in more than 60 countries.

Poverty driven miners rely on inexpensive, outdated, polluting technologies and chemicals because it is what they can afford. Mercury can vaporize and exposure to concentrations above 0.1 mg/m3 can be harmful. At this level, humans cannot detect the Mercury and can be exposed until harmed.

While most gold is produced by major corporations, tens of thousands of people work independently in smaller, artisan operations, in some cases illegal. In Ghana, for instance, the galamseys, independent mine workers, are estimated to number 20,000 to 50,000. In neighboring countries, such workers are called orpailleurs. In Brazil, such workers are called garimpeiros.

A total of about 165,000 tons of gold have been mined in human history, as of 2009. The world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry.

Gold mining is Colombia’s fastest growing industry, with 200,000 small-scale miners producing more than 50 percent of the country’s gold. This growth has turned Colombia into the world’s leading per-capita emitter of mercury, especially in states such as Antioquia.

Ground-level concentrations of mercury gas in gold-processing hamlets like Segovia are so high, experts fear the outbreak of an environmental health crisis worse than any caused by mercury since Minamata, Japan, where releases of mercury from a factory in the mid-20th century killed more than 1,700 people.

Mercury exposure has shown effects such as tremors, impaired cognitive skills, and sleep disturbance in workers with chronic exposure to mercury vapor even at low concentrations   Slightly higher exposure have resulted in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and evidence of interstitial pneumonitis. Acute exposure to mercury vapor has been shown to result in profound central nervous system effects, including psychotic reactions characterized by delirium, hallucinations, and suicidal tendency.  

After the birth of industrial-scale mining in the late 19th century, small-scale mining receded to the corners of crumbling, impoverished Columbian states, offering a refuge for the poor. Unlike larger scale industrial mining operations, small scale mines never abandoned mercury. Cheap, abundant, and easy to use, mercury used in gold mining causes significant mercury pollution. But because of a widespread perception that small-scale mining was no longer a global force, serious efforts to document these toxic emissions only began recently.

In Colombia, two modest technical adjustments (adding mercury after, rather than during, the grinding of ores, and capturing its vapor in ovens) could eliminate nearly all mercury emissions. However, most miners and processors lack the resources to change.

By. Andy Soos

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