The regional government of Pasco, in Peru's central sierra, has convened environmental groups and representatives from government ministries to set up a commission to study the impact of mining operations on the environment and human health, and to propose regulations. Pasco is a prominent mining region of the high plains, with little agriculture and a livestock sector that reports damage from environmental contamination caused by mining practices.

A giant open-pit mine divides in two the city of Cerro de Pasco, the region's capital. Two of its districts, Champamarca and Yanacancha, are surrounded by enormous piles of mining waste that has accumulated over decades.

The evaporation of precipitation from the piles causes acid rain, while the water filtering through the rubble carries ferrous oxide and acids to the nearby San Juan and Mantaro rivers.