Abstract

From a geological standpoint, Chile hosts the largest copper resources in the world and is also the world’s largest producer of copper. In some cases, naturally high arsenic concentrations in Chile are associated with copper-rich deposits which have been mined for centuries. Naturally, copper in Chile is present mainly in the form of sulfides, oxides, and in different mineral deposit types including stratabound, iron oxide copper gold, and porphyry copper deposits. In contrast to copper, arsenic is found in saline precipitates in northern Chile and in volcanic rocks, hot springs, and some mineral deposits present throughout all the regions of Chile. Arsenic was first deemed to be a significant health concern for inhabitants due to chronic exposure in Antofagasta, northern Chile, between 1958 and 1970. Currently, high concentrations of arsenic in that particular region are related to the highest lung cancer rates in the country. Health issues related to human exposure of both elements have existed historically and corresponding environmental guidelines have only been developed recently in Chile. Standards were first enacted in 1994 through the Environmental Framework Law (Law N º 19.300), then through the creation of the National Commission of the Environment (CONAMA) the same year, and the Ministry of the Environment in 2010, which replaced CONAMA. These institutions implemented water regulations and thresholds of 10 μg∙L-1 for arsenic and 2000 μg∙L-1 for copper throughout the entire country. While this effort is a start, the established water guidelines were based on international standards and do not account for natural concentrations found locally within Chile. If arsenic concentrations were interpreted solely based on the established international guidelines, a large proportion of the Chilean territory could be considered uninhabitable. In addition, present environmental regulations in Chile exclude thresholds for all elements in soil and sediments. In summary, the past and present environmental concerns of Chile clearly indicate that natural and anthropogenic sources of arsenic and copper are important to consider in all media (e.g., water, soil, and sediments) as well as within the various regions of the country, which are geologically and hydrologically diverse, to ensure that meaningful, welldeveloped standards exist. Geochemical maps of Chile are presented and interpreted using unpublished and published data of copper and arsenic. Trends show that high background values of both elements exist in barren, unmineralized earth material. In addition, large exceedances are correlated with certain anthropogenic activities. In function of latitude, the total concentrations of arsenic in water generally decrease towards southern Chile. Given the unique geochemical and geological characteristics of the country as well as the historical contamination which has occurred there, the creation of more detailed, region-specific environmental standards is suggested and discussed in accordance with the natural characteristics of each particular region.