Global issues in setting legal limits on soil metal contamination: A case study of Chile

The establishment of legal limits for soil contamination with trace elements is a global issue that has not yet been resolved. However, the resolution of any global problem begins at the national level. In this vein, we present the case of Chile, the world's leading copper producer, where soil contamination by trace elements in mining areas has been severe. We evaluated the magnitude of the ecological and human health risks from exposure to arsenic (As), copper (Cu), zinc (Zn), and lead (Pb) in soils of the La Ligua and Petorca basins, two important mining areas in Chile. Contrary to what might be expected in soils affected by Cu mining activities, As was identified as the most hazardous element in the studied soils, both in terms of ecological and human health risks. On the other hand, Chile does not currently have specific legislation establishing legal limits on soil contamination with trace elements. Since Chile is geochemically similar to New Zealand, Mexico, and Italy, we used the limits of these three countries as benchmarks. We determined the background concentrations of As, Cu, Zn, and Pb in the soils of the two river basins under study and found that they tend to exceed the limits established by foreign laws. We also found that the differences in background elemental concentrations in the studied soils were primarily due to the varied lithology of soil-forming rocks. This means that absolute "one-limit-fits-all" values of element concentrations may not be adequate to regulate the level of soil contamination in areas affected by mining. As a fundamental first step, it is necessary to establish background soil concentrations of trace elements in each river basin in Chile. It is clear that Chile urgently needs to move from rubber-stamping foreign laws to the development of national legislation on soil metal contamination.