Gold panning activities in French Guiana are responsible for a twofold source of mercury pollution: emissions of the elemental form of the metal (Hg°), used as an amalgamating agent, and the erosion of the ancient soils of the Amazon Basin, which are naturally rich in inorganic mercury (HgII). Apart from occupational exposure through inhalation of Hg° (burning of amalgams, gold refining), human contamination stems from the consumption of fishery products, specifically carnivorous and piscivorous fish. They accumulate high concentrations of mercury, exceeding the World Health Organization’s standard of 0.5 μg Hg/g (fresh weight), through biomagnification along food chains of the metal’s organic form, monomethylmercury (MMHg). The latter results from the methylation of HgII by bacteria within anoxic aquatic environments (sediments, dams, etc.). Through cumulative "prey-predator" transfer processes, biomagnification leads to MMHg concentrations in the muscle tissue of fish at the top of food webs that are tens of millions of times higher than those measured in the dissolved fraction of aquatic environments. Thus, human populations that consume these fish daily and in large quantities exhibit mercury levels—estimated by measuring mercury in hair—exceeding the current standard of 10 μg Hg/g. This is the case in French Guiana among the Amerindian communities of the Upper Maroni. Epidemiological studies on children’s psychomotor development conducted among the Amerindians of French Guiana show slight declines in performance on tests measuring motor coordination and visuospatial organization. These results are consistent with the international literature for these exposure levels. Current actions undertaken by health authorities are focused on reducing new exposures and educating Amerindian communities—particularly pregnant and breastfeeding women and young children—to encourage dietary shifts toward consuming the least contaminated fish species.