Pollution by psychoactive pharmaceuticals in the Rivers of Madrid metropolitan area (Spain)

There are a number of reports in the literature which describe the occurrence of so-called emerging pollutants, such as pharmaceuticals, in surface water. Few of these studies have reported values from large cities in relatively arid areas, such as in Spain. The persistence of some pharmaceuticals to usual wastewater treatments allows their discharge into surface waters. It is increasingly evident that mental health problems are of special concern for public health since psychiatric drugs are used in large amounts. Compared to other countries, Spain has a high pharmaceutical consumption rate, and Madrid metropolitan area is one of the most densely populated areas in Europe. The aim of the present study was to determine the presence of different psychoactive pharmaceuticals and metabolites in the main rivers of Madrid metropolitan area: Jarama, Manzanares, Guadarrama, Henares and Tajo. Sampling was done downstream of ten sewage treatment plants (STP) discharging into these rivers. Control points upstream of STPs discharge points were also sampled. Pharmaceutical compounds and metabolites for analysis were selected according to human consumption and prescription rates in Madrid, and the availability of valid techniques for detection. We observed residues of the antidepressants fluoxetine (80% of the sampling sites), citalopram (60%) and venlafaxine (100%), the anxiolytics nordiazepam (90%), oxazepam (80%) and 7-aminoflunitrazepam (10%) and the anticonvulsant carabamazepine (70%). Measured concentrations equalled or exceeded those reported for other geographical areas, although there is a pronounced lack of information for the anxiolytics and venlafaxine. This is of special concern given that Wyeth-Ayerst's venlafaxine, Effexor, was the 10th greatest selling pharmaceutical worldwide in 2006. We conclude that the origin of pharmaceutical pollution in the rivers of Madrid is mainly the discharge of sewage treatment plants in Madrid's metropolitan area and a comprehensive monitoring program should be implemented.