The irrigation or agricultural land with wastewater is increasingly practiced in many parts of the world as a consequence of growing populations and urbanization. The risks emerging from pharmaceuticals that are contained in wastewater for soils and groundwater have hardly been investigated. We studied leaching and effects of naproxen, ibuprofen, bezafibrate, diclofenac, gemfibrocil, clarithromycin, trimethoprim, clindamycin, erythromycin, and metoprolol in a soil column experiment simulating an irrigation event with 8.6 cm of wastewater containing 20 microg L(-1) or 2000 microg L(-1) of each compound or of erythromycin alone. The leached fraction of applied pharmaceuticals ranged from 0.1 +/- 0.1% (clarithromycin, 2000 microg L(-1)) to 130 +/- 41% (naproxen, 20 microg L(-1)) and tended to increase with decreasing K(d) or K(oc). Naproxen transport was similar to that of the tracer chloride. Ibuprofen was also hardly retarded (R = 1.20 +/- 0.18), but showed a higher degradation rate of 0.02 +/- 0.004 h(-1) (2000 microg L(-1)) than naproxen. The transport of a pulse of 2000 microg L(-1) of bezafibrate could be described with a retardation factor of 1.5 and a degradation rate of 0.033 h(-1). The application of erythromycin alone or of a cocktail of all pharmaceuticals significantly increased soil CO2 emissions by 50% 1 d after the application. There is a considerable risk that pharmaceuticals are leached to groundwater during wastewater irrigation.