Helping artisan miners stay clear of mercury
Residents of Colombia’s mining towns are breathing in dangerous levels of mercury as a result of artisanal gold mining, says UBC Mining Engineering Prof. Marcello Veiga.
And mercury contamination may be reaching consumers in far away markets through Columbian food exports, making this little-known environmental problem a global issue.
“This is a poverty-driven activity. These miners aren’t villains. They’re victims,” explains Veiga, the world’s leading researcher on mercury contamination and UN advisor on the global effects of artisanal gold mining which involves small scale, rudimentary and often unsafe mineral extraction.
A powerful toxin that damages the brain and kidneys, mercury is used by artisanal miners to extract gold from ore. Over the past three decades, Veiga has travelled to roughly half of the 80 countries where 15 million men women and children are involved in artisanal gold mining. His mission: bring them vital information on practical, safer alternatives that are good for their health, and better for the environment.
Last year, Veiga and a research team investigated gold production methods and mercury release pathways in five municipalities of Antiquoia, a northeastern province of Colombia. In this remote and mountainous region, there are 17 mining towns and about 30,000 artisanal miners who typically bring back the ore to urban centres for processing.
“The miners feel safer in the towns than staying out in the rural areas where the gold rush has attracted armed guerillas and paramilitary activities,” explains Veiga.
Also involved in this research are Colombia’s central and regional governments and the United Nations Industrial Development Organization’s Colombia Mercury Project. One of the goals is to demonstrate mercury free and also cleaner production technologies, including heavy metal condensing and filtering systems. Led by UBC PhD mining engineering student Paul Cordy, the study appeared in a recent issue of the journal Science of the Total Environment.
The paper details how the miners grind the ore with mercury in small ball mills called “cocos.” During this process, up to 80 per cent of the mercury is lost with the waste, which is then drenched with cyanide to recover any residual gold—often minute quantities.
“In this process, a very toxic compound is formed: mercury-cyanide which is dumped into the local creeks,” say Veiga, adding that this is happening as well in countries such as Peru and Ecuador.
As yet, there have been no studies on the impact of mercury-cyanide on the environment or food chain. However, Veiga says that downstream effects are likely given the number of South American banana plantations and shrimp farms that export to global markets.
However, the most immediate and extreme danger is borne by people who live and breathe in Antiquoia’s towns. Shops where the miners’ gold-ore amalgam is refined simply burn off the mercury without containing or filtering the emissions.
Measuring the air quality in the five towns, the researchers found mercury levels that commonly exceeded 10,000 nanograms per cubic metre—ten times the 1,000 nanograms per cubic metre limit set by the World Health Organization for mercury vapour exposure.
Veiga says, “We found these levels and higher to be common in busy main streets with stores and schools, and with residential neighbourhoods nearby.”
Colombia is the world’s highest per capita mercury polluter due to artisanal gold mining, releasing 130 tonnes of mercury annually into the environment, notes Veiga. Globally, artisanal gold miners are responsible for contaminating air, land and water systems with 1,000 tonnes of mercury each year.
“Ironically, most of the mercury used by artisanal miners is recycled mercury imported from the developed world,”
For related stories please visit