Phosphate mineral fertilizers, trace metals and human health

Abstract

Fertilizers, indispensable as they may seem, are nevertheless materials that also clearly cause serious environmental contamination notably in the agricultural soils. The dire necessity for increased food production has been more marked than ever before. Mineral fertilizers, which are indeed an important nutrient source used for enhanced food production, have unfortunately now become a ‘necessary evil’. Excessive and continuous use of nitrogen and phosphorous fertilizers for decades have converted the agricultural soils into virtual chemical time bombs.

Phosphate rocks by their very geological and mineralogical nature contain a host of environmentally hazardous chemical elements such as Cd, Pb, Hg, U Cr and As among others. The superphosphates are particularly abundant in these hazardous elements and they contaminate the agricultural soils through the use of fertilizer. The leachability and dispersion of some of these toxic elements are most pronounced in some types of soils such as andisols. After the discovery of the dreaded disease ‘Itai-Itai’ cadmium has been listed as one of the most potentially dangerous elements found in phosphate fertilizers. Uranium, apart from its radiotoxicity, is chemotoxic and on account of these two properties, it is considered as a disease causing element. The geochemical pathways lead these toxic elements into food crops, soil, water, air and ultimately the human body tissues via the food chain. Several diseases are known to be caused by the excessive presence of the toxic elements and among them gastrointestinal, pulmonary and kidney ailments are most noteworthy.

Keywords: Geochemical pathways, heavy metals, mineral fertilizers, superphosphates.

doi :10.4038/jnsfsr.v37i3.1219

J.Natn.Sci.Foundation Sri Lanka 2009 37 (3):153-165