Soil pollutants include a large variety of contaminants or chemicals (organic and inorganic), which could be both naturally-occurring in soil and man-made. In both cases, the main soil pollution causes are the human activities (i.e., the accumulation of those chemicals in soil at levels of health risk is due to human activities such as accidental leaks and spills, dumping, manufacturing processes, etc.). Accumulation due to natural processes is also possible, but it has only been recorded in few cases (such as the accumulation of higher levels of perchlorate in soil from Atacama Desert in Chile which is purely due to natural processes in arid environments). Natural processes, however, may have an influence of the human released toxic chemicals (pollutants) in the soil, overall decreasing or increasing the pollutant toxicity and/or the level of contaminated soil. This is possible due to the complex soil environment involving the presence of other chemicals and natural conditions which may interact with the released pollutants.