Mining Methods Vary Widely - Mining and the Environment: From Ore to Metal - page 246

Concentrate
(60 to 100 kg)

Hg
(1 kg or 100%)

Amalgamation

Amalgamation Tailings (lost)
0.5 to 8%

Panning

Hg Excess (recovered)
74 to 94%; Exceptionally 50%

Filtering

Hg Condensed or Lost
5 to 16%; Exceptionally 45%

Heating

FIGURE 5.11
Mercury Balance for Artisanal Gold Mining in Brazil

Hg Volatilized (lost)
0.05 to 4%

Gold Melting

In Latin America, up to 200 t/y gold are produced
by artisanal mining, releasing more than 200 t/y
of mercury into the environment.
Source:
Fharid et al. 1992

Bullion

drinking and bathing purposes. Monitoring of situations where there has been widespread
use of mercury, for example near the Talawaan small-scale mining complex, shows ele-
vated concentrations of dissolved mercury in surface water supplies used for bathing and
drinking. High concentrations of mercury are also found in stream bed sediments, ensur-
ing a continuing source of mercury long after gold recovery activities end. The mercury
may also accumulate in i lter-feeding organisms such as shelli sh, and may bio-magnify
along the food chain. Consumption of aquatic organisms therefore provides an additional
potential exposure pathway for local people and those living downstream.
Health effects of mercury vary, depending on the chemical form in which the mercury
occurs. Organic forms of mercury are more toxic, with methyl mercury being the most
toxic. Methyl mercury was implicated in causing Minimata disease, which was i rst dis-
covered in 1956, and which was responsible for killing more than 1,000 people in Japan.
Allegations of Minimata disease from small-scale mining operations have been made
but have not been substantiated, and it appears that most of the mercury contamination
remains in an inorganic form. Ingestion or dermal contact with inorganic mercury may
adversely affect the central nervous system and endocrine system and damage the mouth,
gums, and teeth. High exposure over long periods of time results in brain damage caus-
ing mental illness ( 'mad hatters' disease') and ultimately death. Early symptoms may be
subtle and difi cult to distinguish from those of other maladies. Serious health effects may
take many years to appear. In typical gold rush situations in remote parts of developing
countries with poor sanitation and low life expectancy, the effects of mercury poisoning
may never be recognized. This may explain why the results of monitoring indicating
dangerously high exposure to mercury, do not seem to generate the levels of concern that
would be expected among the people involved. A campaign by the Bureau of Mines and
Geosciences in the Philippines to persuade small-scale miners to use simple condensers to
enable mercury to be recovered and re-used, proved unsuccessful, despite the equipment

In typical gold rush situations
in remote parts of developing
countries with poor sanitation
and low life expectancy, the
effects of mercury poisoning may
never be recognized.