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signs of contamination, 97 and another study concluded that half the miners living in thelower Caroní River manifested signs of mercury poisoning. 98• The extent of deforestation attributed to mining is not known. However, one studyestimates that small-scale miners deforest approximately 40,000 hectares per year. 99The indirect impacts of mining are likely to be more serious. An analysis of population change in theregion suggests that some mining communities become frontier settlements, eventually providing apoint of departure for further settlement and migration (see Question 10). The number of small-scaleminers appears to have declined in the last few years due to depressed gold prices. 100 This wouldsuggest that impacts may have diminished, although an increase in gold prices and a lack of economicalternatives could reverse this trend.The Impact of Mercury on the Environment and Human HealthBOX 8Small-scale miners wash metallic mercury through sluices. Metallic mercury can be absorbed through the skin, presentinga health risk to miners who handle the material in their sluicing operations. The mercury/gold amalgamation thatresults from washing is subsequently burned to release the mercury, leaving gold particles behind. Mercury can enter intothe environment in two ways: 1) when miners fail to capture mercury as it is washed through the sluice, and 2) when minersburn the mercury amalgam to separate the gold from the mercury. When mercury is oxidized it remains in organismsand can bioaccumulate over time. Oxidation occurs when miners breathe mercury vapors released during the burningprocess. In a process that is not entirely understood by scientists, metallic mercury can also be transformed intomethylmercury when it is released into rivers and streams. This toxic compound is subsequently consumed by aquaticorganisms, increasing in concentration as it moves up the food chain.Mercury poisoning can result in damage to the nervous system, birth defects, or death. Even minimal exposure tomethylmercury can have serious consequences, and women and children are particularly at risk. In pregnant women,methylmercury can be transferred through the placenta to the fetus, leading to severe birth defects even in cases where themother’s symptoms are mild.Source: M. Veiga, "Mercury in Small-scale Gold Mining in Latin America: Facts, Fantasies and Solutions" Paper presented to UNIDO ExpertGroup Meeting, Vienna: July 1-3, 1997.Information on the impacts of medium and large-scale mines is not available, but given the characteristicsof the Guayana region, there is a significant potential for negative environmental impacts.No data are available on the impacts of existing large and medium-scale mines in the Guayanaregion. Obtaining such information would require extensive field work, which was not conductedfor this report. However, the Guayana region is characterized by high rainfall (between 1500 and4000 mm per year), with few dry months throughout the year. 101 Some of the wettest parts of theGuayana region have been allocated for mining. High rainfall carries with it a potential risk that thetailings impoundments typically constructed to store cyanide and other waste from industrial miningprocesses will overflow, although it may also help to dilute any spills.Gold mining and ore processing generally include production and use of heavy metals. If improperlymanaged, waste containing heavy metals can contaminate nearby streams and groundwater. 102Given the importance of rivers for fish consumption at the local and regional level, mining in theGuayana region must be carefully monitored to ensure that companies comply with strict environmentalstandards.63