The need for a reassessment of the safe upper limit of selenium in drinking water

Results of recent epidemiologic studies suggest the need to reassess the safe upper limit in drinking water ofselenium, a metalloid with both toxicological and nutritional properties. Observational and experimentalhuman studies on health effects of organic selenium compounds consumed through diet or supplements,and of inorganic selenium consumed through drinking water, have shown that human toxicity may occurat much lower levels than previously surmised. Evidence indicates that the chemical form of seleniumstrongly influences its toxicity, and that its biological activity may differ in different species, emphasizingthe importance of the few human studies on health effects of the specific selenium compounds found indrinking water. Epidemiologic studies that investigated the effects of selenate, an inorganic selenium speciescommonly found in drinking water, together with evidence of toxicity of inorganic selenium at low levelsin from in vitro and animal studies, indicate that health risks may occur at exposures below the currentEuropean Union and World Health Organization upper limit and guideline of 10 and 40 μg/l, respectively,and suggest reduction to 1 μg/l in order to adequately protect human health. Although few drinking watersare currently known to have selenium concentrations exceeding this level, the public health importance ofthis issue should not be overlooked, and further epidemiologic research is critically needed in this area.