Environmentalists in El Salvador and Guatemala have expressed concern about the dumping of polluted waters from the Cerro Blanco mining project, in Jutiapa, Guatemala, into the Ostua river. The Ostua flows into the Guija lake, and later across the border into the Lempa River, which is the primary source of freshwater for over 3 million Salvadorans. Water from the Lempa is used for hydroelectric power, agriculture, fishing, household needs, and drinking water, and supports the livelihoods of many families.
The runoff from the mines can contain high levels of fluorine, arsenic, and boron, at a temperature of 35 degrees celsius, causing thermal pollution and damaging the entire ecosystems of the affected bodies of water. In addition, scientists believe that the pollution will effect any water sources, animals, plants, or human communities in the area. Social organizations in El Salvador and Guatemala have attempted to stop the construction of the mine, but so far no agreement has been reached.