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Threat of mercury poisoning rises with gold mining boom

By Shefa Siegel - posted Tuesday, 25 January 2011


It is unclear what made the night of Atehortua’s poisoning different from other nights. One theory is that the unusually late shift occurred in the entable just as the air temperature was dropping and the day’s accumulated mercury vapour was precipitating from the ceiling. What is clear is the attack on Atehortua’s nervous system ought to have sounded alarms about an imminent threat to the urban residents of Antioquia’s mining regions.

“There is no other case in the world like this where an urban population of 150,000 people is exposed to such high levels of mercury vapour,” says Marcello Veiga, a professor of geochemistry and mining engineering at the University of British Columbia and former director of the United Nations Global Mercury Project. “The entables must move from the cities.”

Ordinarily, gold processing occurs in rural districts or industrial zones, away from densely-populated areas. But in Colombia, where security forces are preoccupied battling violence from all directions, the risks of working in the bush are too extreme to operate unprotected. (While I was there last fall, bandits robbed and murdered four brothers at their mine.) So gold refiners seek the security of city centres. In Segovia and four nearby cities, an estimated 350 entables release 50 to 100 metric tons of mercury each year into the air and soil of northeast Antioquia.

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Yet cases where mercury-afflicted miners return to work in heavily contaminated areas remain common because of the Colombian Health Ministry’s practice of testing urine rather than blood; only blood tests can gauge how much mercury may have reached a person’s brain. “When the level of mercury in urine is normal,” Veiga says, “the patient can return to the same polluted work environment, without any evaluation of how much mercury has accumulated in the brain.”

Meanwhile, evidence is accumulating that more chronic varieties of the acute symptoms endured by Atehortua are affecting the most vulnerable segment of the population. In neurological tests administered to 196 children in Segovia, aged 7 to 13, 96 per cent failed at least one measure of intoxication, whose indicators include attention, memory, language, and executive functions. These data are included in a UN health report, published in January, which describes the mercury situation in Antioquia as “dramatic”.

“It is no exaggeration,” the report concludes, “that in Segovia and Remedios” - the towns are adjacent - “the proportion of the population exposed to a high risk of mercury intoxication approaches 100 per cent.”

After the birth of industrial-scale mining in the late 19th century, small-scale mining receded to the corners of crumbling, impoverished states, offering a refuge for the global poor - “drought-driven work” - during periods of privation and crop failure. Unlike industrial mining operations, small-scale mines never abandoned mercury. Cheap, abundant, and easy to use, mercury used in gold mining causes 30 per cent of global mercury pollution, eclipsing all sources except mercury gas emitted from coal-fired power plants. 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 in the last decade.

In Colombia, two modest technical adjustments - adding mercury after, rather than during, the grinding of ores, and capturing its vapour in ovens - could eliminate nearly all mercury emissions from entables. But most miners and processors lack the resources to change, while the country’s culture of conflict means there are no easy solutions.

Operating entables inside municipal limits has been illegal in Colombia since 1995, when a federal decree gave mayors a ten-year window to relocate refineries. Ten years turned into 15. The federal government pointed to the state agencies, the state to the mayors, the mayors to the miners, all to no effect. The mayors did not want to lose their votes. They also did not want to lose their lives.

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At a September meeting of 55 public officials in Medellin, Miguel Enrigue Franco Menco, the mayor of Nechí - another gold mining town in Antioquia - issued a sober lament of his state’s mercury crisis. “Responsibility falls on the mayors,” he said. “But behind the gold market there is violence threatening us, and public officials are turning a blind eye to this problem. We have fear.”

The mayor of Nechí was countered, swiftly and unsentimentally, by a vow from the region’s attorney-general, Fanny Enriquez, to imprison any mayor who failed to move the entables. “Comply with the law!” she cried into a microphone, drowning protests from miners and mayors.

During my recent trip to Colombia, I had planned to tour entables in Segovia, but protests over the arrival of a Canadian mining company made that journey impossible. Trade union leaders were persuading miners that UN efforts to curb mercury emissions were part of a foreign conspiracy to expropriate their mines under environmental pretence.

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First published by Yale Environment 360 on January 3, 2011.



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About the Author

Shefa Siegel directs the US State Department’s technical assistance program with small-scale miners in the Andes. From 2005-2007 he was External Relations Advisor for the United Nations Global Mercury Project. He works at the intersections of environmental politics, economic development, and global health, and teaches ecological thought at Royal Roads University on Vancouver Island. He is a fellow in the politics of mining at the University of British Columbia.

Creative Commons LicenseThis work is licensed under a Creative Commons License.

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