Influence of illegal gold mining on mercury levels in fish of north Sulawesi's Minahasa Peninsula, (Indonesia).

North Sulawesi's Minahasa Peninsula currently is experiencing intense illegal gold mining activity. It has been estimated that 200 t of mercury are used annually in Indonesia in the recovery of gold from the illegal mines. To date no study has assessed the environmental impact of this illegal activity on the nearby aquatic biota. To address this concern, we compared tissue mercury levels from several sites, including a reference site and a site near an illegal mine. Fish from the region of the illegal mine contained 30 times the mercury content of fish at the reference site. Moreover, whole fish tissue levels were four times those recommended by the World Health Organization for consumption restrictions and often two-fold higher than recommended for total restriction on fish consumption. The environmental and human health implications of these levels are of grave concern; citizen education programmes are required to alert indigenous peoples of the risks associated with mercury exposure and fish consumption guidelines put into place. A more comprehensive effort to identify major sources and effects are required. Such information can be used to determine the correct course of action that needs to be taken to close existing illegal mines and prevent future illegal mining activities.