Nonylphenol and estrogenic activity in aquatic environmental samples

We surveyed a series of surface waters and sewage treatment plants in Flanders (north of Belgium) for the presence of estrogenic activity and a xeno-estrogenic compound para-nonylphenol (NP), respectively. The surface waters of rural origin, used for drinking water production, were free of significant levels of estrogenic activity and NP (<1 mu g/L). Domestic sewage, after proper treatment, appeared to be no major source of this chemical. Yet, in some industrial effluents and surface waters of highly industrialized regions, NP and/or estrogenic activity was prominent, that is, <1 to 122 mu g NP/L and 11 to 42 mu g NP/L, respectively; This is because of the ongoing use of NP polyethoxylates in industry. The response of the recombinant yeast estrogen assay to the environmental samples tested was not consistent with the detected concentrations of NP. Standard addition of a natural estrogen, 17 beta-estradiol, generated no or a reduced response compared to the standard curve concentration. Application of humic acids to standard series of NP and 17 beta-estradiol resulted in a dose-dependent decrease of the estrogenic response. It appears that this bioassay is subject to considerable interferences due to the complexity of environmental samples. Parallel implementation of extensive chemical screening for xenobiotics and use of the bioassay are needed for adequate assessment of the potential estrogenic hazard to avoid false negative evaluations.