The Tapajos River Basin in the Brazilian Amazon is the location of one of the largest concentrations of artisanal and small-scale miners in the world. Today, 40,000 miners produce 8 t of gold annum(-1) and at least double this amount of mercury is released into the environment. This region was selected under the Global Mercury Project, a United Nations program that aims to reduce the environmental and health impacts caused by mercury through the application of cleaner technologies and increased awareness. A group of educators provided support to miners, training 4200 people in 141 mining locations. The effectiveness of this training was evaluated based on 20 performance indicators. After 120 days of training, an absolute improvement of approximately 29% had been achieved. As a result of this training, it is estimated that annual mercury emissions in Tapajos have been reduced by 1762 kg or around 10% of the total mercury released in the region.