http://www.greenpeace.org/~thoml/mercury.html (Einblicke ins Internet, 10/1995)Mercury has been used in gold mining in Brazil since gold was first discovered in the Amazon basin in the 18th century. In the last ten years, between 1-2,000 tons of this highly poisonous liquid metal have been released into the Amazon Basin.
Mercury levels are increasing as more gold is mined. For every kilo of gold produced, four times that amount of mercury is released into the environment. Concern over the contamination of the Amazon river and of local populations is escalating with hundreds of thousands of people living in the region thought to be at risk.
Scientists have referred to the presence of such high levels as a "chemical time bomb"; levels of poisoning that are likely to appear in the Amazon may eclipse Bhopal or any comparable case of industrial poisoning.
The current gold rush started as a result of rapid increases in the price of gold in 1979, and the goldfields are now reported to involve over one million miners or 'garimpeiros'. It shows no sign of abating.
The metallic mercury is not produced in any of these countries, but rather, these are the countries where exporting companies have their headquarters. Mercury used in Brazil is produced in Spain, Italy, the United States and Mexico.
The majority of mercury imported into Brazil is resold by wholesalers to the goldmining sector, without any government control. It is usually sold in packaging indicating its use for dentistry.
Mercury in the amalgam is later burnt off, releasing a toxic white vapour and leaving near-pure gold ore. About three quarters of the mercury used in goldmining is released into the atmosphere, where it is absorbed by plants and soils in contaminated rain.
Between 40 and 200 tons of gold is produced each year from the Amazon using mercury amalgam techniques. Alternatively, gold is excavated from rock, as seen in the dramatic photographs taken by world-famous photographer, Sebastiao Salgado of the mine at Serra Pelado, in the state of Para.
The goldmining activities themselves also dramatically change the river environment; as the sediment is disturbed clear waterways turn to rivers of opaque golden brown. However, the ecological effects of this stark alteration of the river environment have been poorly studied.
Added to the accumulated contamination of the Amazon ecosystem (both aquatic and aerial), is the serious risk posed to the health of hundreds of thousands of people living in the region. People are exposed to mercury both directly in mining operations and indirectly as it moves through the environment into the human food supply.
Mercury vapour is inhaled as it is released when the mercury/gold amalgam is burnt in open air containers. The elderly, children and pregnant women, whose health is more vulnerable, are particularly at risk.
Recent surveys in the goldmining town of Itaituba, which has the largest concentration of gold traders in the Brazilian Amazon, show that up to 37 per cent of miners have excessive levels of mercury in their blood. Itaituba is in the Tapajos valley, the largest of nine major goldmining regions in the Amazon Basin.
Distance from mining operations is little protection as mercury moves widely through the environment. Blood and urine samples taken from individuals in the fishing village of Jacareacanga, Š100km from the nearest mining camp, had significantly elevated levels of mercury, with 16 per cent showing exceedingly high levels in their bodies. Kayapo children have also been found to have average blood levels more than twice the acceptable upper limits.
Other samples show dangerously high levels of mercury in floordust in gold workshops in Itaituba which are a major source of atmospheric mercury and human exposure.
Current research is focusing on developing simple methods of reducing occupational exposure to mercury vapour, by using filters or fume cupboards. Although there is no practical alternative to the use of mercury itself, the garimpo method of extraction can be conducted without mercury. But this requires more skill and any miners not using mercury are generally regarded as eccentric's by their peers.
In addition, the use of "retorts" (simple enclosed cooking vessels) in place of open pans in the amalgam process can reduce atmospheric emissions by up to 99 per cent. But the use of retorts is rare among gold mining communities who are still largely ignorant of the dangers and have little concern for the environmental impact of their work.
Since Brazil relies entirely on imports for its mercury supplies, the control of these imports is put forward as one answer to the problem.