Environmental occurrence of selenium in waters and related health significance

Appreciable amounts of selenium in spring and well waters can be found due to geological occurrence. Concentrations of as much as 400-9000 micrograms/l have been reported in U.S. waters. These levels are 8 to 180 times the current EPA drinking water standard and approximate dietary exposures of 4900 micrograms in selenosis regions of China. Reviews of health significance of the elevated drinking water exposures to U.S. populations revealed elevated concentrations of selenium in urine and blood. A decrease in glutathione peroxidase activity in such instances was noted. However noticeable symptoms and signs seem absent in studies reviewed. A comparison of intake levels (diet or drinking water) to urinary excretion for residents of China and the U.S. produced a correlation coefficient, r = 0.82 (P < 0.01) for the three research studies available.