title: Evaluating the fish safety level of river water and wastewater with a larval medaka assay.
abstract: A larval medaka (Oryzias latipes) assay was proposed to evaluate the fish safety level of river waters and wastewaters. Organic toxicants were 10-100 times concentrated with adsorption cartridges from 4 l of river water or 1-10 times concentrated from 400 ml of wastewater. Toxicity of these concentrated solutions was determined by exposing 48-72 h post-hatch age larvae for 48 h. The method effectively revealed a variation of the median lethal concentration ratio (LCR50) from 13 to >100 in 125 river water samples, and from <1 to >10 in five typical wastewater samples. Ayase River, which takes water mostly from agricultural or household discharge, showed significantly (P<0.001) lower LCR50 than Sagami River that takes natural water as the source. Safety Levels in both Sagami River and Ayase River were influenced by the irrigation activity, LCR50 at some sites showing a seasonal-specific decrease in winter. Pollution from pulp and paper industries contributed to the low LCR50 in several tributaries of Ayase River. Required little manpower in sampling, pretreatment and testing, the proposed larval medaka assay was proved as an efficient tool for screening those high risk sites for priority management.
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, 79 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan. rui-liu@ynu.ac.jp
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Takashi
authors.initials: T
authors.lastname: Kameya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Sugimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Kubo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sawai
authors.forename: Kohei
authors.initials: K
authors.lastname: Urano
mesh_terms: D000818:Animals; D004784:Environmental Monitoring / Q000379:methods; D005399:Fishes; D005618:Fresh Water / Q000032:analysis*; D007814:Larva / Q000187:drug effects; D019055:No-Observed-Adverse-Effect Level; D009990:Oryzias / Q000254:growth & development*; D012722:Sewage / Q000032:analysis*; D052616:Solid Phase Extraction; D018675:Toxicity Tests / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical