Ecological risk of nonylphenol in China surface waters based on reproductive fitness.

It has been recognized that ecological risk assessment based on traditional endpoints of toxicity are unable to provide adequate protection because some chemicals may affect reproductive fitness of aquatic organisms at much lower concentrations. In this paper, predicted no effect concentrations (PNECs) for 4-nonylphenol (NP) were derived based either on endpoints of survival, development, and growth or on some nonlethal biomarkers of reproduction, biochemical and molecular biology data. The PNECs derived from reproductive lesion ranged from 0.12 to 0.60 μg NP L(-1), which was significantly lower than those derived from other endpoints. An assessment of ecological risks posed by NP to aquatic organisms in surface waters of China was conducted based on concentration levels of NP in 16 surface waters of 4 major river basins and PNECs derived from reproductive fitness by a tiered ecological risk assessment (ERA). The results showed that 14.2% and 76.5% of surface waters in China may have ecological risks resulting from reproductive fitness if the thresholds of protection for aquatic organisms were set up as 5% (HC5) and 1% (HC1), respectively. The risks were significantly greatest in the Yangtze River Basin than in other major river basins. In comparison with the risks assessed based on traditional endpoints, such as lethality, for those chemicals causing adverse effects on reproduction due to modulation of endocrine function, to be protective of ecosystem structure and function, lesser PNECs, based on sublethal effects of reproduction, were appropriate.