Abstract
Selenium is an essential trace element for many organisms, including humans, but it is toxic at higher level than homeostatic levels. Both selenium deficiency and toxicity are problems around the world (specially in China, India, USA). The level of selenium in selected waters of Ethiopia (including Akaki Kality river and some of its tributaries such as Kebena, Saris Abo, and Estifanos areas; bottled waters like Yes, Aqua Safe and Gift; well waters like Ziqualla Wogem, Akaki Kality and Ferensay Legasion; and tap water at Arat Kilo) were determined by microwave plasma-atomic emission spectroscopy after wet digestion and acidification. The levels selenium determined (µg/L) were 7.0, 3.1, 6.4, 3.9, 6.3, 5.0, 5.4, 0.66, 4.2, 6.3, and 2.0, respectively. The percentage recovery of Se was found to be 95.2% which is in the acceptable range. The ANOVA result showed that there is a significant difference between the mean levels of selenium in the river, well and bottles waters. The results obtained in this study were compared with the permissible limit (10 µg/L) set by Ethiopian Standards Agency and the tolerable level set by WHO (< 40 µg/L). Thus the levels of selenium detected in this study are within the recommended limit.
 
 KEY WORDS: Selenium, Trace metal, Water samples, Microwave plasma-atomic emission spectroscopy, Ethiopia
 
 Bull. Chem. Soc. Ethiop. 2020, 34(2), 215-226.
 DOI: https://dx.doi.org/10.4314/bcse.v34i2.1
Highlights
Selenium is a relatively rare trace element, ranking 68th among the elements in the Earth’s crust [1]
The anthropogenic activities in Addis Ababa city are the possible causes for the higher level of selenium in Akaki Kality River water while the natural existence of selenium in Ziqulla Wogem well water is at the lowest level
This study was carried out to determine the level of selenium in some of the selected water samples of Ethiopia by MP-AES
Summary
Selenium is a relatively rare trace element, ranking 68th among the elements in the Earth’s crust [1]. Selenium plays a key role in several major metabolic pathways such as thyroid hormone metabolism, antioxidant defense systems, and immune functions [4], has a supposed inhibitory effect in acquired immunodeficiency syndrome (AIDS) development and has beneficial roles in reproduction, cardiovascular diseases, and mood disorders [5,6,7,8]. Selenium may play a detoxication effect due to the mutual antagonism with mercury and arsenic [9,10,11,12]. This protective role of selenium against mercury toxicity depends on the molar ratio between them but it is difficult and premature to establish a value [9]. A high (400 μg per day) intake of selenium causes pulmonary edema, abdominal pain, jaundice, chronic gastrointestinal diseases, hair loss and fatigue in humans and its deficiency result in Keshan disease, iodine deficiency disorders, and thyroid function, cancer, cardiovascular disease, and reproduction problem which are frequently reported in China [13]
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