Strategic survey of therapeutic drugs in the rivers Po and Lambro in northern Italy

A survey was done in the river Po (Italy) to check for therapeutic drugs in the environment. A number of pharmaceuticals were selected for analysis on the basis of high consumption and excretion as parent compound in humans. Eight sampling stations along the rivers Po and Lambro made it possible to plot the patterns of contamination in a highly populated region with a large number of animal farms. Atenolol, lincomycin, erythromycin, clarithromycin, bezafibrate, and furosemide were present at all the sampling sites, and other drugs were found only in some. Concentrations ranged from 0.1 to 250 ng/L, and several drugs exceeded the trigger value (10 ng/L) suggested by recent documents from the European Agency for the Evaluation of Medicinal Products (EMEA), assessing environmental risks for these chemicals. The patterns of contamination showed differences among sub-basins which correlated with the presence of large human settlements and/or animal farms. The ratio of measured to predicted concentrations (MEC/PEC) allowed a gross division of the drugs into two groups. The first consisted of pharmaceuticals with a MEC/PEC in the range 0.01-0.3, where the ratio is probably determined by the environmental behavior and the extent of degradation of the molecule. The other group consisted of pharmaceuticals found at concentrations higher than those predicted (MEC/PEC > 1). In this group, which consists of drugs sold without prescription or for veterinary use, market justifications (sales load uncertainty) have more role than chemical properties and environmental fate in explaining the differences between measured and predicted environmental concentrations.