Quicksilver for Gold
The poisoning of the Amazon
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.
International trade
All the mercury used in Brazil is imported. Historically, up to 90 per cent
of mercury imported into Brazil came from Mexico, but in the last
decade there has been a significant increase in imports from Holland,
Germany and the United Kingdom.
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.
The mercury connection
Metallic mercury is used as an amalgam to separate particles of gold
from river sediment. During the simple process of adding liquid mercury
to filtered sediment, some of this highly toxic substance escapes directly
into the water and soils. S
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 risks
Metallic mercury escapes into the rivers where it is transformed into the
highly toxic and persistent methyl mercury which builds up in the food
chain, ultimately accumulating in high concentrations in fish; the staple
diet of local people.
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.
The reality
Levels of mercury found among people in goldmining areas are high
enough to produce clinical symptoms of mercury poisoning. In its most
advanced form mercury poisoning can result in birth defects, brain
damage and death. Less severe poisoning may result in tunnel vision,
instability and neurological disorders.
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, S100km 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.
Alternatives
The simplicity of the mercury amalgam process has made equally
user-friendly alternative technologies difficult to find. Other amalgam
agents such as arsenic are just as toxic and in order to be adopted,
alternatives must be cheap, simple and easy to use.
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.
Greenpeace demands
A complete ban on the use of mercury in the environment.
In the short-term, Greenpeace is calling for increased regulation and
restriction in the use of mercury in the Amazon environment as a
first step towards a ban on the use of this highly toxic metal.
Research into workable and environmentally-friendly alternatives to
the use of mercury in goldmining activities.
Support and education for the goldminers in finding alternative
activities which do not pose a threat to the Amazon ecosystem.
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