Abstract
Methodology development for the population-level ecological risk assessment of chemicals with potential endocrine disruption has become a research focus in recent years. A multigeneration full-life-cycle experiment on 4-nonylphenol (4-NP) using S-rR strain medaka was designed and conducted with this focus. This paper provides an overview of the experiment and presents some of the important results of the experiment. The experiment was designed for three generations (approximately 70 days per generation) to determine 1) the effectiveness and biological significance of each of the orthodox endpoints for endocrine disruption from the standpoint of population-level impact, 2) the correlations between the respective endpoints, 3) the possibility of intergenerational sensitivity, and 4) the incidence between the males and females, S-rR strain medaka was employed due to its biological merit of hereditary difference in body color for male and female, which is useful for the detection of a slight endocrine disruption effect on secondary sexual characteristics and reproduction. Seventeen β-estradiol (E2) compounds were used as a positive control. Fertility, the frequency of testis-ovum appearance in the male gonad, and the secondary sexual characteristics were found to have good dose-effect relationship. None of strengthened effect expressed in most of the measure endpoints for 4-NP and E2 were observed to cross from one generation to another. Males were more sensitive than females.
