Pharmaceutical substances found in waters of Spain's Doñana National Park

Five anti-inflammatory drugs (diclofenac, ibuprofen, ketoprofen, naproxen and salicylic acid), a nervous system stimulant (caffeine), two antibiotics (sulfametoxazol and trimethoprim), two lipid regulators (clofibric acid and gemfibrozil), an anti-epilepsy drug (carbamazepine), a beta blocker (propranolol) and four hormones (three natural: oestrone, 17β-oestradiol and oestriol; and one artificial: 17α-ethynyloestradiol) have all be found in Doñana.

"Ibuprofen is the compound we found at the highest concentrations. Each year, 140 kg of this drug are discharged into the main Doñana tributaries via urban waste water from the surrounding area," says Esteban Alonso, lead author of the study and a researcher at the Department of Analytical Chemistry at the US.

This pioneering study, which has been published in the Journal of Hazardous Materials, shows that "the primary source of these drugs in the waterways flowing into Doñana (the Guadiamar river, Partido stream and La Rocina stream) is treated waste water from nearby towns," points out Alonso.

These compounds, consumed and metabolised by people, are discharged in the form of urine and faeces via the sewerage systems in towns surrounding Doñana into water treatment plants.

"These are discharged into the Park's water resources, inevitably, 24 hours a day, 365 days per year," the researcher adds. According to the scientist, the technologies used to treat water are "insufficient," and currently only remove rather more than 60%, "with significant variations from one drug to another."

In order to eliminate these kinds of compounds and other associated ones from the waters of Doñana, the scientists recommend implementing tertiary treatment systems at the existing treatment plants, based around oxidation processes or membrane systems. A threat to aquatic ecosystems

The research team has carried out a preliminary estimate of the eco-toxicological risks, and has found that certain levels of drugs pose a risk to aquatic organisms such as Hydra attenuata.

Previous experiments carried out by the team, in collaboration with the University of Stirling (United Kingdom), have shown that exposure over the course of five days to different drugs causes alteration in various genes in the liver and brain of the Atlantic salmon.

Now, the scientists will transfer these results to native species living in the water systems of Doñana in order to "better understand the way these compounds influence genetic expression," says Alonso.