Nationwide supplementation of sodium selenate to commercial fertilizers: history and 25-year results from the Finnish selenium monitoring programme.

Selenium is unevenly distributed in soils worldwide. For climatic and geochemical reasons, Finland is one of the low-selenium regions in the world. To improve the quality of Finnish foods and animal health and to increase the selenium intake of the population, an official decision was made in 1984 to supplement compound fertilizers with selenium. Practically all fertilizers used in Finland have contained selenium since 1985. The objective of this chapter is to report the effects of the supplementation of selenium to commercial fertilizers on soils, feeds, basic foodstuffs, dietary selenium intake, human tissues and the environment. Within a monitoring programme, sampling of cereals, basic foodstuffs, feeds, fertilizers, soils and human tissues has been carried out at least annually since 1985. The systematic error in selenium analyses has been followed annually by a quality assessment scheme involving seven participating laboratories. The selenium concentration of spring cereals increased on average 15-fold compared with the level before the selenium fertilization practice. The mean selenium concentration in beef and pork increased six- and twofold, respectively, and in milk threefold, compared with levels before selenium fertilization. The average dietary intake increased from 0.04 mg Se/day to a plateau of 0.07 mg Se/day in the mid-2000s. Foods of animal origin in 2006 contributed over 75% of the total daily intake of selenium. The mean human plasma selenium concentration increased by 60% and the selenium status is optimal. Evident signs of selenium transport into natural waters have not been found. In Finland, where the geochemical conditions are relatively uniform, the nationwide supplementation of fertilizers with selenium has proved to be an effective, safe and controlled way of bringing the selenium intake of the whole population to the recommended level. Moreover the well-being of animals has been secured.