Occurrence and environmental behavior of the chiral pharmaceutical drug ibuprofen in surface waters and in wastewater

Pharmaceutical compounds can reach detectable concentrations in rivers and lakes if production and use are sufficiently large and the compounds show s ome mobility and persistence in the aquatic environment. In this study, we report on the occurrence and on the enantiomer composition of the chiral ph armaceutical drug ibuprofen (IB) in surface waters and in samples from wast ewater treatment plants (WWTPs). Enantioselective gas chromatography and de tection by mass spectrometry/mass spectrometry was used for analysis. IB wa s present in influents of WWTPs at concentrations of up to 3 mu g/L with a high enantiomeric excess of the pharmacologically active S enantiomer (S mu ch greater than R), as from human urinary excretion. The principal human ur inary metabolites of IB, hydroxy-IB and carhoxy-IB, were observed in WWTP i nfluents at even higher concentrations. In contrast to other pharmaceutical compounds such as clofibric acid and diclofenac, IB and its meta bolites a re then efficiently degraded (>95%) during treatment in WWTPs. Laboratory incubation experiments confirmed this rapid degradation. In rivers and lake s, IB was detected at concentrations of up to 8 ng/L, generally with some e xcess of the S enantiomer; the IB metabolites were not detected (<1 ng/L). Incubation of lake water fortified with (rac)-IB indicated a faster dissipa tion of the S enantiomer, thus resulting eventually in residues with a reve rsed (R > S) enantiomer composition as compared to that from human metaboli sm. Inefficient WWTPs and direct discharges of untreated wastewater from st orm events, however, can still he a source for increased levels of IB in su rface Water.