. The Conservation Atlas of Tropical Forests: the Americas. * Gold mming areas Figure 1 Most concern has been expressed about the long-term implications of the unregulated mercury use in mining camps. Gold production levels are a rough guide to the order of magnitude of mercury use: if 100 metric tonnes are produced annually, an equal amount of mercury will have been vaporised in the production process. A further 200-300 metric tonnes can be assumed to have escaped in spillages from machinery. There is a growing body of infor- mation about mercury levels in sediments, soils and river water, ba
. The Conservation Atlas of Tropical Forests: the Americas. * Gold mming areas Figure 1 Most concern has been expressed about the long-term implications of the unregulated mercury use in mining camps. Gold production levels are a rough guide to the order of magnitude of mercury use: if 100 metric tonnes are produced annually, an equal amount of mercury will have been vaporised in the production process. A further 200-300 metric tonnes can be assumed to have escaped in spillages from machinery. There is a growing body of infor- mation about mercury levels in sediments, soils and river water, based on field sampling in all major goldfields. There is some information on mercury levels in fish, and only fragmentary data on human contamination. Fish with mercury levels up to 8 times higher than the EEC Environmental Quality Standard have been recorded in the Tapajos and Madeira Rners. The most comprehensive sam- pling of mercury levels in human populations so far carried out, by an Anglo-Brazilian research team in the Tapajos valley in 1990, found blood mercury levels were signifi- cantly higher among riverine fish-eating communities some way from mining areas than among the miners themselves. No generalised contamination was found among the popula- tion of a major gold trading centre. This suggests that fish- eating is a more important contamination pathway than inhaling vapour, and, paradoxically, that it is not the miners themselves who are most at risk. It is likely that the first cases of Minanata disease, caused by acute methyl mercury poisoning, will be recorded in the Brazilian Amazon before the turn of the centurv. of the natural vegetation. Current plans identify a target of 170,000 sq. km, or per cent of the region. In contrast, preser- vation of 25 per cent of the original vegetation of the region was recommended in 1979 by the Interministerial Commission on Forest Policy in the original version of the draft law drawn up by the commission (see Feamside, 1
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