1. Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Kita 18 Nishi 9, Kita-Ku, Sapporo, Hokkaido 060-0818, Japan
2. Department of Chemistry, College of Natural and Computational Science, University of Gondar, P.O. Box 196, Gondar, Ethiopia
3. Water Research Group, School of Environmental Sciences and Development, North-West University, Private Bag X6001, Potchefstroom, South Africa