Factors controlling the distribution of selenium in the environment and their impact on health and nutrition

Se is essential to and animal health but call be toxic ill excess. An interest in its geochemistry has developed alongside a greater understanding of its functions in a number of health conditions. Geology exerts a strong control oil the Se status of the surface environment: low-Se rock-types (0.05-0.09 mg Se/kg) make up the majority of rocks occuring at the Earth's surface, which in turn account for the generally low levels of Se in most soils. However. there tire exceptions such as associations With Sulfide mineralisation and in some types of sedimentary rocks (e.g. black shales) in which contents of Se can be much higher. Baseline geochemical data now enable it comparison to be made between environmental and human Se status, although a direct link is only likely to be seen if the population is dependent oil the local environment for Sustenance. This situation is demonstrated with an example from the work of the British Geological Survey in the Se-deficiency belt of China. The recent fall in the daily dietary Se intake in the UK is discussed in the context of human Se status and declining use of, North American wheat in bread making, Generally. US wheat has tell times more Se than UK wheat. attributed to the fact that soils front the wheat-growing, belt of America are more enriched in Se to it similar order of magnitude. In agriculture effective biofortification of crops with Se-rich fertilisers must be demonstrably sale to the environment and monitored appropriately and baseline geochemical data will enable this process to be done with confidence.