that all the metal contaminations can be attributed to the mining activities on the main gold zone of Colombia and San Jorge River basin. Human exposure and risk assessment In placer mining, mercury is added to the material extracted from the alluvial deposits. Excess mercury is discharged into adjacent waterways along with other residues of the ore which enters into the local ecosystem. Mercury grows into a greater threat to health as it moves through the aquatic food chain. In the aquatic environment, the elemental “quicksilver” form of mercury is taken by the bacteria and algae and is converted into the far more dangerous methylmercury. As methylmercury travels up the food chain, from algae to plankton to small fish to big fish, it becomes progressively more concentrated. When humans consume fish that contains methyl mercury, it is absorbed into the human body through gastrointestinal system. Mercury can enter the brain and cross the placenta. Once methylmercury enters the human body, it is relatively difficult to eliminate methylmercury from the body as it is bound to proteins. The effects of methylmercury on developing fetus were tragically demonstrated in Minimata, Japan. Children born to mothers who consumed mercury-contaminated fish suffered devastating birth defects, particularly those affecting the nervous system. When humans consume contaminated fish, they suffer neurological damage and autoimmune disorders. In addition, methylmercury can cause IQ loss, delayed speech and other neuro-developmental deficits among children when exposed. Early life exposures are the most harmful as they can damage the whole brain. Later life exposures may result in localized damage to the cerebellum, visual cortex, and motor strip. In adults, these exposures can lead to visuospatial problems and effects on executive functioning, memory and mood. Prevention Colombian government has been putting effort to reduce mercury usage levels. The adoption in July 2013 of Law 1658 to reduce and eliminate mercury use is an important step. It aims to phase out the use of mercury in all production processes within ten years and in mining within five years. Awareness has to be brought in miners regarding the risks involved in using mercury. In addition to the awareness, miners should be introduced to new techniques that minimize mercury use or provided with safer alternatives that can replace mercury amalgamation. According to Sam Spiegel, a lecturer in international development at the University of Edinburgh, “efforts to lower mercury emissions should aim to support miners and