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(29-04) Risk assessment of 4-nonylphenol by a population-level approach using life-cycle toxicity data for Medaka (Oryzias latipes). Lin, Bin-Le*,1, Miyamoto, Kenichi1, Yoshida, Kikuo1, Nakanishi, Junko1,2, 1 Research Center for Chemical Risk Management, National Institute of Advanced Industrial Science and Technology, Tsukuba city, Ibaragi Prefecture2 Institute of Environmental Science and Technology, Yokohama National University, Yokohama city, Kanagawa Prefecture ABSTRACT- Ecological risk assessment for endocrine disrupters should be based on ecologically relevant endpoints related to the ability of populations to survive, grow, and reproduce, rather than on supplemental observations at a serum and tissue level. To meet this urgent need, we attempted to quantitatively assess the potential impact of 4-nonylphenol on Medaka (Oryzias latipes) in terms of reduction of population growth rate and enhanced risk of population extinction. We first developed an age-classified projection matrix (daily time-step) model. We then used it as a tool to incorporate life-cycle survivorship and fecundity data obtained for individual-level responses of Medaka exposed to 4-nonylphenol into population-level responses such as the intrinsic rate of population growth (r). A dose-response-curve model between exposure concentration and r was derived and analyzed. Together with rational assumptions of equilibrium population size and environmental variance, these estimates provided a basis for a prediction of the enhanced extinction risk of Medaka populations exposed to 4-nonylphenol. Key words: Population-level effect, Ecological risk assessment, Nonylphenol, Fish |
