Selenium is a naturally occurring trace element that is nutritionally required in smallamounts but it can become toxic at concentrations only twice those required. The narrow mar-gin between beneficial and harmful lev...Selenium is a naturally occurring trace element that is nutritionally required in smallamounts but it can become toxic at concentrations only twice those required. The narrow mar-gin between beneficial and harmful levels has important implications for human activities thatincrease the amount of selenium in the environment. Two of these activities, disposal of fbssilfuel wastes and agricultural irrigation of arid, seleniferous soils, have poisoned fish andwildlife, and threatened public health at several locations in the United States. Research stud-ies of these episodes have generated a data base that clearly illustrates the environmental hazardof excessive selenium. It is strongly bioaccumulated by aquatic organisms and even slight in-creases in waterborne concentrations can quickly result in toxic effects such as deformed em-bryos and reproductive failure in wildlife. The selenium data base has been very beneficial indeveloping hazard assessment procedures and establishing environmentally sound water qualitycriteria. The two faces of selenium, required nutrient and Potent toxin, make it a particularlyimportant trace element in the health of both animals and man. Because of this paradox, envi-ronmental selenium in relation to agriculture, fisheries, and wildlife wiIl continue to raise im-POrtant land and water management issues for decades to come. If these issues are dealt withusing prudence and the available environmental selenium data base, adverse irnpacts to naturalresources andspublic health can be avoided展开更多
Appreciable amounts of selenium in spring and well waters can be found due to geological occurrence. Concentrations of as much as 400 9000 μg/l have been reported in U. S. waters.These levels are 8 to 180 times the c...Appreciable amounts of selenium in spring and well waters can be found due to geological occurrence. Concentrations of as much as 400 9000 μg/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 4900μg 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展开更多
文摘Selenium is a naturally occurring trace element that is nutritionally required in smallamounts but it can become toxic at concentrations only twice those required. The narrow mar-gin between beneficial and harmful levels has important implications for human activities thatincrease the amount of selenium in the environment. Two of these activities, disposal of fbssilfuel wastes and agricultural irrigation of arid, seleniferous soils, have poisoned fish andwildlife, and threatened public health at several locations in the United States. Research stud-ies of these episodes have generated a data base that clearly illustrates the environmental hazardof excessive selenium. It is strongly bioaccumulated by aquatic organisms and even slight in-creases in waterborne concentrations can quickly result in toxic effects such as deformed em-bryos and reproductive failure in wildlife. The selenium data base has been very beneficial indeveloping hazard assessment procedures and establishing environmentally sound water qualitycriteria. The two faces of selenium, required nutrient and Potent toxin, make it a particularlyimportant trace element in the health of both animals and man. Because of this paradox, envi-ronmental selenium in relation to agriculture, fisheries, and wildlife wiIl continue to raise im-POrtant land and water management issues for decades to come. If these issues are dealt withusing prudence and the available environmental selenium data base, adverse irnpacts to naturalresources andspublic health can be avoided
文摘Appreciable amounts of selenium in spring and well waters can be found due to geological occurrence. Concentrations of as much as 400 9000 μg/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 4900μg 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
