"Approaches for population-level risk assessment: a case study of 4-nonylphenol using life-cycle toxicity data for Medaka (Oryzias latipes)." 

Lin Bin-Le

National Institute of Advanced Industrial Science and Technology

SETAC 23rd Annual Meeting in North America (Salt Lake City, USA 2002/11/19)

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Abstract

The ecological risk for chemicals should be evaluated from the viewpoint of population-level impacts. To this date, however, still no any practical approach available for real chemicals management action appears. Toward this urgent need, this paper firstly proposed two of the population-level approaches based on its state-of-arts, and then as a case study applied the two approaches to the quantitative assessment of the potential impact of 4-nonylphenol (4-NP) on medaka (Oryzias latipes) in terms of reduction of population growth rate (λ). 

An age-classified population matrix model (daily time-step) was developed and used as a tool to incorporate life-cycle survivorship and fecundity data obtained for individual-level responses of medaka exposed to 4-NP into population-level responses such as λ. 

Two of the proposed population-level approaches based on the resulted λs were then examined: to derive the predicted no effect concentration (PNEC) for population-level impacts based on the threshold concentration defined as the chemical concentration at λ=1 and the lowest-observed-effect concentration (LOEC), no-observed-effect concentration (NOEC), and maximum-acceptable-toxic concentration (MATC). 

The results suggest a range of PNEC for medaka population growth impact under the exposure of 4-NP as 0.82 to 2.10 μｇ/ｌ. Although such two approaches still have their limitations, current knowledge indicates that they are the most reasonable and practicable approaches for evaluating population-level risk.

Keywords

Ecological risk assessment, Population-level impacts, 4-Nonylphenol, Medaka