Genesis of seleniferous soils and associated animal and human health problems

Abstract

Abstract The soils containing selenium (Se) high enough to produce forages and grain crops with toxic level of Se for animal and human consumption are designated as seleniferous soils. Seleniferous soils located in several countries around the globe were developed under the action of similar factors and processes on the parent material as for the normal soils, but the parent material inherently contained high Se levels. Nevertheless, different anthropogenic activities like burning of fossil fuels, use of fertilizers, sewage sludge, and underground water for raising crops have also contributed to Se enrichment of soils. The baseline values of natural or geogenic Se in the soils revealed the extent to which soils may have been contaminated by anthropogenic activities over a period of time. Except that the farm produce contained high Se levels and many a times not suitable for human or animal consumption, the overall productivity potential of seleniferous soils is not adversely influenced due to high Se levels. The geochemical and soil characteristics control the speciation of Se, solid-phase distribution, and concentration in food components, which in turn determine the daily Se intake by animals and humans in a region. Daily intake of Se in human beings varied from 30 to 6690 μg day− 1 with the highest levels reported from the seleniferous regions. Consumption of > 400 μg Se day− 1 may lead to serious health hazards in humans. Chronic or acute Se toxicity causes loss of hair and nails in humans and blind staggers and alkali disease in livestock.