. >> manuani miner john valdez works with mercury almost every day. miners can also be exposed to mercury vapors. that's because once they extract their amalgam - they have to burn off the mercury to get to the gold. >> so these miners are touching mercury, they're breathing mercury, what are the health effects? >> so, the type of mercury that these miners are exposed to is extremely toxic, especially when you breathe it. it starts to affect, the liver, kidneys the digestive system and starts to affect the central nervous system. >> today the manuani miners aren't working because of the rain. but john valdez showed me the equipment he used just two days ago to burn mercury off a piece of gold. >> everything we've been seeing it's for this - this is about 3 grams of gold or a hundred dollars, which the average worker can make in about 3 days. that's a lot of money in madre de dios. the average farm worker makes less than $200 a month. that lure of gold, is changing the face of the amazon as jungle is replaced by mining camps like this magnets for crime