Ozonation is used as additional wastewater treatment option to remove recalcitrant micropollutants. It also removes the estrogenic activity found in wastewater but not always the anti-estrogenic activity. This can be explained by an incomplete removal of anti-estrogenic micropollutants or by formation of transformation products (TPs) which retain the activity. The present study investigates the degradation of the anti-estrogenic pharmaceutical tamoxifen in pure water, regarding TP formation and related anti-estrogenic effect using Arxula adeninivorans yeast estrogen screen (A-YES). In total, five transformation products were detected: three N-oxides and two further products (TP 270 and TP 388). For the transformation product TP 270 a correlation of the extent of formation with an increase of the anti-estrogenic activity was determined, demonstrating that transformation products from ozonation can be more active in a bioassay than the parent compounds. Our study shows also that the transformation of tamoxifen to N-oxides reduces the anti-estrogenic activity. The reactivity of amines towards ozone typically increases with pH, since only deprotonated amines react with ozone. Hence, removal of the endocrine activity by N-oxide formation may be disfavored at low pH.
Keywords: Anti-estrogenic effect; Endocrine disruptive compounds; Micropollutants; Ozone; Transformation products; Water treatment.
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