【Paper】
Comprehensive Biological Assessment of Leachate from Waste Disposal Landfill Site by Medaka, Oryzias latipes
Kae Osaki*, Shosaku Kashiwada**, Norihisa Tatarazako*** and Yoshiro Ono*
* Graduate School of Natural Science and Technology, Okayama University
** Nicholas School of the Environment and Earth Sciences,
Duke University, USA
*** National Institute for Environmental Studies
† Correspondence should be addressed to Yoshiro Ono:
Graduate School of Natural Science and Technology, Okayama University
（3-1-1 Tsushima-naka, Okayama, 700-8530 Japan）


Abstract
Leachate from waste disposal landfill site and its treated leachate are usually monitored with chemical analyses for environmental safety. Although it is impossible to analyze all chemicals, treated leachates are released into river water. In this study, bioassay by medaka fish（Oryzias latipes）were used to estimate the comprehensive biological effects of leachate; 1） Lethal effects on larvae and adults; and hatch-inhibition were measured for acute toxicities; 2） Induction of CYP1A was measured for xenobiotics（PAHs or dioxin like compounds）exposure as EROD activity; 3） Vitellogenin（Vtg）was induced in male medaka fish for exposure to xenoestrogens（an endocrine disruptor）. The leachate exhibited lethal toxicities to adults and larvae, and delayed hatching. These toxic effects disappeared in the treated leachate. Abnormal larvae were observed from embryos exposed to leachate and treated leachate. EROD activities disappeared in treated leachate as well as in the lethal toxicity test. Vtg inductions still remained in the treated leachates. These results suggest that leachate treatments are useful in removing chemicals that cause lethal and/or hatch-inhibition effects. However, the leachate treatment exhibited limited effects for the removal of mutation substances and xenoestrogens from leachate.


Key words: medaka, leachate, vitellogenin, EROD, ecotoxicology