Donana National Park (Southern Spain) is one of the most emblematic protected areas in Europe and is included in UNESCO's World Heritage List. A 1-year monitoring study was carried out to investigate the presence of 16 pharmaceutical compounds belonging to seven therapeutic groups in wastewater discharges, rivers and streams affecting Donana Park. Fourteen pharmaceuticals were detected in effluent wastewater at concentration levels up to 26.8 mu g L-1 and thirteen were detected in surface water at concentration levels up to 4.55 mu g L-1. Ibuprofen was the compound at the highest concentration levels. An increase of the concentration levels in surface water was observed in summer months due to the reduction of the flow rates of the rivers. Nevertheless, risk quotient values estimated in surface water were lower than one so no toxicological effect is suspected to occur. The highest average risk quotients were obtained for ibuprofen (risk quotient 0.67 +/- 0.28), gemfibrozil (risk quotient 0.52 +/- 0.33). propranolol (0.13 +/- 0.06) and naproxen (0.10 +/- 0.09). Nevertheless, in summer months, risk quotient values up to 9.3 and 10.7 were estimated for the estrogenic compounds 17 alpha-ethinylestradiol and 17 beta-estradiol. (c) 2010 Elsevier B.V. All rights reserved.