1. Water Research Group, Unit for Environmental Science and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
2. Laboratory of Toxicology, Department of Environmental Veterinary Science, Hokkaido University, Kita 18, Nishi 9, Kita ku, Sapporo 060–0818, Japan
3. Department of Environmental Veterinary Science, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita ku, Sapporo 060–0818, Japan