Pharmaceutical compounds can reach detectable concentrations in rivers and lakes if production and use aresufficientlylargeandthecompoundsshowsomemobility and persistence in the aquatic environment. In this study, we report on the occurrence and on the enantiomer composition of the chiral pharmaceutical drug ibuprofen (IB) in surface waters and in samples from wastewater treatment plants (WWTPs). Enantioselective gas chromatography and detection by mass spectrometry/mass spectrometry was used for analysis. IB was present in influents of WWTPs at concentrations of up to 3 µg/L with a high enantiomeric excess of the pharmacologically active S enantiomer ( S . R ), as from human urinary excretion. The principal human urinary metabolites of IB, hydroxy-IBandcarboxy-IB,wereobservedinWWTPinfluents at even higher concentrations. In contrast to other pharmaceutical compounds such as clofibric acid and diclofenac,IBanditsmetabolitesarethenefficientlydegraded (>95%) during treatment in WWTPs. Laboratory incubation experiments confirmed this rapid degradation. In rivers and lakes, IB was detected at concentrations of up to 8 ng/L, generally with some excess of the S enantiomer; the IB metabolites were not detected (<1 ng/L). Incubation of lake water fortified with ( rac )-IB indicated a faster dissipation of the S enantiomer, thus resulting eventually in residues with a reversed ( R > S ) enantiomer composition as compared to that from human metabolism. Inefficient WWTPsanddirectdischargesofuntreatedwastewaterfrom storm events, however, can still be a source for increased levels of IB in surface water.

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