"Approaches for Establishing Predicted-no-effect Concentrations for Population-Level Ecological Risk Assessment in the Context of Chemical Substances Management" 

LIN Bin-Le, Akihiro Toukai, Junko Nakanishi

National Institute of Advanced Industrial Science and Technology

ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol.39 pp.4833-4840 (2005)

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Abstract

The establishment of rational frameworks for population-level ecological risk assessment (PLERA) in the context of chemical substances management is an important issue. We illustrate two feasible approaches for establishing predicted-no-effect concentrations (PNECs) for PLERA through a case study of 4-nonylphenol (4-NP) using life-cycle toxicity data for medaka (Oryzias latipes). We first quantified the potential impacts of 4-NP on medaka in terms of reduction of population growth rate (��). An age-classified population matrix model (daily time-step) was developed and used to combine life-cycle survivorship and fecundity data obtained from individual-level responses of medaka exposed to 4-NP into population-level responses defined by the parameter ��. Thereafter, from the resulting ��s, two approaches for establishing population-level PNEC values were proposed and examined. The PNEC values for population-level impacts, based on a) the threshold concentration defined as the chemical concentration at which �� = 1 as a value with a 95% confidence intervals, and b) the no-observed-effect concentration (NOEC) and the maximum-acceptable-toxic concentration (MATC), were then derived. The results suggest that PNEC values of 4-NP ranging between 0.82 and 2.10 ��g/L affect medaka population growth. Although these approaches still have their limitations, current knowledge indicates that they are reasonable and practical for evaluating population-level impacts of chemicals, thereby serving as a case study for establishing PNEC values for PLERA in the context of chemical substances management and decision making.

Keywords

Predicted-no-effect Concentrations,Population-Level Ecological Risk Assessment, Nonylphenol, Medaka